[1/4] drm: add generic zpos property

Commit Message

Benjamin Gaignard May 11, 2016, 10:25 a.m. UTC

This patch adds support for generic plane's zpos property property with
well-defined semantics:
- added zpos properties to plane and plane state structures
- added helpers for normalizing zpos properties of given set of planes
- well defined semantics: planes are sorted by zpos values and then plane
  id value if zpos equals

Normalized zpos values are calculated automatically when generic
muttable zpos property has been initialized. Drivers can simply use
plane_state->normalized_zpos in their atomic_check and/or plane_update
callbacks without any additional calls to DRM core.

Signed-off-by: Marek Szyprowski <[e-mail]>

Compare to Marek's original patch zpos property is now specific to each
plane and no more to the core.
Normalize function take care of the range of per plane defined range
before set normalized_zpos.

Signed-off-by: Benjamin Gaignard <[e-mail]>

Cc: Inki Dae <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Ville Syrjala <[e-mail]>
Cc: Joonyoung Shim <[e-mail]>
Cc: Seung-Woo Kim <[e-mail]>
Cc: Andrzej Hajda <[e-mail]>
Cc: Krzysztof Kozlowski <[e-mail]>
Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
Cc: Tobias Jakobi <[e-mail]>
Cc: Gustavo Padovan <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Laurent Pinchart <[e-mail]>

---
 Documentation/DocBook/gpu.tmpl      |  10 ++
 drivers/gpu/drm/Makefile            |   2 +-
 drivers/gpu/drm/drm_atomic_helper.c |   6 +
 drivers/gpu/drm/drm_blend.c         | 284 ++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_crtc_internal.h |   3 +
 include/drm/drm_crtc.h              |  25 ++++
 6 files changed, 329 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/drm_blend.c

Comments

Laurent Pinchart May 11, 2016, 11:24 a.m. UTC | #1

Hi Benjamin,

Thank you for the patch.

I would have started working on this next week, thanks for beating me to it 
:-)

On Wednesday 11 May 2016 12:25:05 Benjamin Gaignard wrote:
> This patch adds support for generic plane's zpos property property with
> well-defined semantics:
> - added zpos properties to plane and plane state structures
> - added helpers for normalizing zpos properties of given set of planes
> - well defined semantics: planes are sorted by zpos values and then plane
>   id value if zpos equals
> 
> Normalized zpos values are calculated automatically when generic
> muttable zpos property has been initialized. Drivers can simply use
> plane_state->normalized_zpos in their atomic_check and/or plane_update
> callbacks without any additional calls to DRM core.
> 
> Signed-off-by: Marek Szyprowski <[e-mail]>
> 
> Compare to Marek's original patch zpos property is now specific to each
> plane and no more to the core.
> Normalize function take care of the range of per plane defined range
> before set normalized_zpos.
> 
> Signed-off-by: Benjamin Gaignard <[e-mail]>
> 
> Cc: Inki Dae <[e-mail]>
> Cc: Daniel Vetter <[e-mail]>
> Cc: Ville Syrjala <[e-mail]>
> Cc: Joonyoung Shim <[e-mail]>
> Cc: Seung-Woo Kim <[e-mail]>
> Cc: Andrzej Hajda <[e-mail]>
> Cc: Krzysztof Kozlowski <[e-mail]>
> Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
> Cc: Tobias Jakobi <[e-mail]>
> Cc: Gustavo Padovan <[e-mail]>
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: Laurent Pinchart <[e-mail]>
> 
> ---
>  Documentation/DocBook/gpu.tmpl      |  10 ++
>  drivers/gpu/drm/Makefile            |   2 +-
>  drivers/gpu/drm/drm_atomic_helper.c |   6 +
>  drivers/gpu/drm/drm_blend.c         | 284 +++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_crtc_internal.h |   3 +
>  include/drm/drm_crtc.h              |  25 ++++
>  6 files changed, 329 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/drm_blend.c
> 
> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> index 9dd48f7..0df6abb 100644
> --- a/Documentation/DocBook/gpu.tmpl
> +++ b/Documentation/DocBook/gpu.tmpl
> @@ -2151,6 +2151,16 @@ void intel_crt_init(struct drm_device *dev)
>  		the underlying hardware).</td>
>  	</tr>
>  	<tr>
> +	<td valign="top" > "zpos" </td>
> +	<td valign="top" >RANGE</td>
> +	<td valign="top" >Min= driver dependent, Max= driver dependent</td>
> +	<td valign="top" >Plane</td>
> +	<td valign="top" >Plane's 'z' position during blending operation (0 for
> background, highest for frontmost).
> +		If two planes assigned to same CRTC have equal zpos values, the plane
> with higher plane
> +		id is treated as closer to front. Can be IMMUTABLE if driver doesn't
> support changing
> +		planes' order. Exact value range is driver dependent.</td>
> +	</tr>
> +	<tr>
>  	<td rowspan="20" valign="top" >i915</td>
>  	<td rowspan="2" valign="top" >Generic</td>
>  	<td valign="top" >"Broadcast RGB"</td>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 2bd3e5a..df88253 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -2,7 +2,7 @@
>  # Makefile for the drm device driver.  This driver provides support for the
> # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
> 
> -drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
> +drm-y       :=	drm_auth.o drm_bufs.o drm_blend.o drm_cache.o \
>  		drm_context.o drm_dma.o \
>  		drm_fops.o drm_gem.o drm_ioctl.o drm_irq.o \
>  		drm_lock.o drm_memory.o drm_drv.o drm_vm.o \
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> b/drivers/gpu/drm/drm_atomic_helper.c index 997fd21..f10652f 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -32,6 +32,8 @@
>  #include <drm/drm_atomic_helper.h>
>  #include <linux/fence.h>
> 
> +#include "drm_crtc_internal.h"

drm_atomic_helper_normalize_zpos() is declared in <drm/drm_crtc.h>, why do you 
need to include drm_crtc_internal.h ?

>  /**
>   * DOC: overview
>   *
> @@ -587,6 +589,10 @@ drm_atomic_helper_check_planes(struct drm_device *dev,
>  	struct drm_plane_state *plane_state;
>  	int i, ret = 0;
> 
> +	ret = drm_atomic_helper_normalize_zpos(dev, state);
> +	if (ret)
> +		return ret;
> +
>  	for_each_plane_in_state(state, plane, plane_state, i) {
>  		const struct drm_plane_helper_funcs *funcs;
> 
> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> new file mode 100644
> index 0000000..7017715
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_blend.c
> @@ -0,0 +1,284 @@

[snip]

> +#include <linux/slab.h>
> +#include <linux/sort.h>
> +#include <linux/export.h>
> +#include <drm/drmP.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_atomic.h>

Nitpicking, could you please keep header files alphabetically sorted ? It 
helps locating and avoiding duplicates.

> +#include "drm_internal.h"
> +
> +#define MAX(a, b) (((a) > (b)) ? (a) : (b))

linux/kernel.h has max and max_t, is there really a need for a new macro ?

> +/**
> + * drm_plane_atomic_set_zpos_property - set plane zpos property
> + * @plane: drm plane
> + * @state: drm plane state
> + * @property: must be the zpos property associated to the plane
> + * @val: zpos value to be set
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
> +				       struct drm_plane_state *state,
> +				       struct drm_property *property,
> +				       uint64_t val)
> +{
> +	struct drm_mode_object *obj = &plane->base;
> +	int i;
> +
> +	for (i = 0; i < obj->properties->count; i++) {
> +		if (obj->properties->properties[i] == property) {
> +			state->zpos = val;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(drm_plane_atomic_set_zpos_property);

Why do you need this function instead of adding zpos support to 
drm_atomic_plane_set_property() ? Same question for the get handler.

> +/**
> + * drm_plane_atomic_get_zpos_property - set plane zpos property
> + * @plane: drm plane
> + * @state: drm plane state
> + * @property: must be the zpos property associated to the plane
> + * @val: zpos value to be retrieve
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
> +				       const struct drm_plane_state *state,
> +				       struct drm_property *property,
> +				       uint64_t *val)
> +{
> +	struct drm_mode_object *obj = &plane->base;
> +	int i;
> +
> +	for (i = 0; i < obj->properties->count; i++) {
> +		if (obj->properties->properties[i] == property) {
> +			*val = state->zpos;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(drm_plane_atomic_get_zpos_property);
> +
> +/**
> + * drm_plane_create_zpos_property - create mutable zpos property
> + * @plane: drm plane
> + * @min: minimal possible value of zpos property
> + * @max: maximal possible value of zpos property
> + *
> + * This function initializes generic mutable zpos property and enables
> support
> + * for it in drm core. Drivers can then attach this property to planes to
> enable
> + * support for configurable planes arrangement during blending operation.
> + * Once mutable zpos property has been enabled, the DRM core will
> automatically
> + * calculate drm_plane_state->normalized_zpos values. Usually min should be
> set 
> + * to 0 and max to maximal number of planes for given crtc - 1.
> + *
> + * If zpos of some planes cannot be changed (like fixed background or
> + * cursor/topmost planes), driver should adjust min/max values and assign
> those
> + * planes immutable zpos property with lower or higher values (for more
> + * information, see drm_mode_create_zpos_immutable_property() function). In
> such
> + * case driver should also assign proper initial zpos values for all planes
> in
> + * its plane_reset() callback, so the planes will be always sorted
> properly.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_create_zpos_property(struct drm_plane *plane,
> +				   unsigned int min, unsigned int max)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create_range(plane->dev, 0, "zpos", min, max);
> +	if (!prop)
> +		return -ENOMEM;
> +

You should cache prop (in drm_mode_config) instead of recreating it for each 
plane, like done for the other properties. Same in the next function.

> +	drm_object_attach_property(&plane->base, prop, min);
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_create_zpos_property);
> +
> +/**
> + * drm_plane_create_zpos_immutable_property - create immuttable zpos
> property
> + * @plane: drm plane
> + * @min: minimal possible value of zpos property
> + * @max: maximal possible value of zpos property
> + *
> + * This function initializes generic immutable zpos property and enables
> + * support for it in drm core. Using this property driver lets userspace
> + * to get the arrangement of the planes for blending operation and notifies
> + * it that the hardware (or driver) doesn't support changing of the
> planes'
> + * order.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
> +					     unsigned int min, unsigned int max)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create_range(plane->dev, DRM_MODE_PROP_IMMUTABLE,
> +					 "zpos", min, max);

Can two properties exist with the same name but different flags (immutable and 
mutable) ? Or with different min/max values ? I don't expect min/max to be 
different for every plane, so maybe a function that creates the zpos property 
once with min/max values and a second one that attaches the property to planes 
would be a better API.

> +	if (!prop)
> +		return -ENOMEM;
> +
> +	drm_object_attach_property(&plane->base, prop, min);
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_create_zpos_immutable_property);
> +
> +static int drm_atomic_state_zpos_cmp(const void *a, const void *b)
> +{
> +	const struct drm_plane_state *sa = *(struct drm_plane_state **)a;
> +	const struct drm_plane_state *sb = *(struct drm_plane_state **)b;
> +	int zpos_a = (sa->zpos << 16) + sa->plane->base.id;
> +	int zpos_b = (sb->zpos << 16) + sb->plane->base.id;
> +
> +	return zpos_a - zpos_b;

Instead of playing tricks with the ids that will create a dependency on the 
plane id value range, how about

	if (sa->zpos != sb->zpos)
		return sa->zpos - sb->zpos;
	else
		return sa->plane->base.id - sb->plane->base.id;

> +}
> +
> +/**
> + * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos values
> + * @crtc: crtc with planes, which have to be considered for normalization
> + * @crtc_state: new atomic state to apply
> + *
> + * This function checks new states of all planes assigned to given crtc and
> + * calculates normalized zpos value for them. Planes are compared first by
> their
> + * zpos values, then by plane id (if zpos equals). Plane with lowest zpos
> value
> + * is at the bottom. The plane_state->normalized_zpos is then filled with
> unique
> + * values from 0 to number of active planes in crtc minus one.
> + *
> + * RETURNS
> + * Zero for success or -errno
> + */
> +int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
> +					  struct drm_crtc_state *crtc_state)
> +{
> +	struct drm_atomic_state *state = crtc_state->state;
> +	struct drm_device *dev = crtc->dev;
> +	int total_planes = dev->mode_config.num_total_plane;
> +	struct drm_plane_state **states;
> +	struct drm_plane *plane;
> +	int i, zpos, n = 0;
> +	int ret = 0;
> +
> +	DRM_DEBUG_ATOMIC("[CRTC:%d:%s] calculating normalized zpos values\n",
> +			 crtc->base.id, crtc->name);
> +
> +	states = kmalloc(total_planes * sizeof(*states), GFP_KERNEL);
> +	if (!states)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Normalization process might create new states for planes which
> +	 * normalized_zpos has to be recalculated.
> +	 */
> +	drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
> +		struct drm_plane_state *plane_state =
> +			drm_atomic_get_plane_state(state, plane);
> +		if (IS_ERR(plane_state)) {
> +			ret = PTR_ERR(plane_state);
> +			goto fail;
> +		}
> +		states[n++] = plane_state;
> +		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] processing zpos value %d\n",
> +				 plane->base.id, plane->name,
> +				 plane_state->zpos);
> +	}
> +
> +	sort(states, n, sizeof(*states), drm_atomic_state_zpos_cmp, NULL);
> +
> +	for (i = 0, zpos = 0; i < n; i++, zpos++) {
> +		plane = states[i]->plane;
> +
> +		zpos = MAX(zpos, states[i]->zpos);
> +
> +		states[i]->normalized_zpos = zpos;

Can't you just use i instead of MAX(zpos, states[i]->zpos) ?

> +		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] normalized zpos value %d\n",
> +				 plane->base.id, plane->name, zpos);
> +	}
> +	crtc_state->zpos_changed = true;
> +
> +fail:

We reach the label in the normal code path too, I would thus call it done or 
exit instead of fail.

> +	kfree(states);
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_crtc_normalize_zpos);
> +
> +/**
> + * drm_atomic_helper_normalize_zpos - calculate normalized zpos values for
> all
> + *				      crtcs
> + * @dev: DRM device
> + * @state: atomic state of DRM device
> + *
> + * This function calculates normalized zpos value for all modified planes
> in
> + * the provided atomic state of DRM device. For more information, see
> + * drm_atomic_helper_crtc_normalize_zpos() function.
> + *
> + * RETURNS
> + * Zero for success or -errno
> + */
> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
> +				     struct drm_atomic_state *state)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_plane *plane;
> +	struct drm_plane_state *plane_state;
> +	int i, ret = 0;
> +
> +	for_each_plane_in_state(state, plane, plane_state, i) {
> +		crtc = plane_state->crtc;
> +		if (!crtc)
> +			continue;
> +		if (plane->state->zpos != plane_state->zpos) {
> +			crtc_state =
> +				drm_atomic_get_existing_crtc_state(state, crtc);
> +			crtc_state->zpos_changed = true;
> +		}
> +	}
> +
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +		if (crtc_state->plane_mask != crtc->state->plane_mask ||
> +		    crtc_state->zpos_changed) {
> +			ret = drm_atomic_helper_crtc_normalize_zpos(crtc,
> +								    crtc_state);
> +			if (ret)
> +				return ret;
> +		}
> +	}
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_normalize_zpos);
> diff --git a/drivers/gpu/drm/drm_crtc_internal.h
> b/drivers/gpu/drm/drm_crtc_internal.h index a78c138..37d9068 100644
> --- a/drivers/gpu/drm/drm_crtc_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_internal.h
> @@ -42,3 +42,6 @@ int drm_atomic_get_property(struct drm_mode_object *obj,
>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>  			  void *data, struct drm_file *file_priv);
> 
> +/* drm_blend.c */
> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
> +				     struct drm_atomic_state *state);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index d1559cd..a34bc29 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -305,6 +305,7 @@ struct drm_plane_helper_funcs;
>   * @mode_changed: crtc_state->mode or crtc_state->enable has been changed
>   * @active_changed: crtc_state->active has been toggled.
>   * @connectors_changed: connectors to this crtc have been updated
> + * @zpos_changed: zpos values of planes on this crtc have been updated
>   * @color_mgmt_changed: color management properties have changed (degamma
> or *	gamma LUT or CSC matrix)
>   * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
> @@ -340,6 +341,7 @@ struct drm_crtc_state {
>  	bool mode_changed : 1;
>  	bool active_changed : 1;
>  	bool connectors_changed : 1;
> +	bool zpos_changed : 1;
>  	bool color_mgmt_changed : 1;
> 
>  	/* attached planes bitmask:
> @@ -1263,6 +1265,9 @@ struct drm_connector {
>   *	plane (in 16.16)
>   * @src_w: width of visible portion of plane (in 16.16)
>   * @src_h: height of visible portion of plane (in 16.16)
> + * @zpos: priority of the given plane on crtc (optional)
> + * @normalized_zpos: normalized value of zpos: unique, range from 0 to N
> + *	 for given crtc

If N is the number of active planes that would be 0 to N-1. If N is the number 
of active planes minus one then this is correct :-)

>   * @state: backpointer to global drm_atomic_state
>   */
>  struct drm_plane_state {
> @@ -1283,6 +1288,10 @@ struct drm_plane_state {
>  	/* Plane rotation */
>  	unsigned int rotation;
> 
> +	/* Plane zpos */
> +	unsigned int zpos;
> +	unsigned int normalized_zpos;
> +
>  	struct drm_atomic_state *state;
>  };
> 
> @@ -2554,6 +2563,22 @@ extern struct drm_property
> *drm_mode_create_rotation_property(struct drm_device extern unsigned int
> drm_rotation_simplify(unsigned int rotation,
>  					  unsigned int supported_rotations);
> 
> +extern int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
> +					      struct drm_plane_state *state,
> +					      struct drm_property *property,
> +					      uint64_t val);
> +

You can drop the extern keywords, they're not needed. I know that lots of 
functions in this header file use extern, but not all of them do, and moving 
forward I don't see a big reason to keep using unneeded keywords.

> +extern int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
> +					      const struct drm_plane_state *state,
> +					      struct drm_property *property,
> +					      uint64_t *val);
> +
> +extern int drm_plane_create_zpos_property(struct drm_plane *plane,
> +					  unsigned int min, unsigned int max);

Shouldn't this be named drm_plane_attach_zpos_property() instead ? The main 
purpose of the function is to attach the property, even if it has to create it 
on first invocation as a side effect.

> +extern int drm_plane_create_zpos_immutable_property(struct drm_plane
> *plane,
> +						    unsigned int min,
> +						    unsigned int max);
> + 
>  /* Helpers */
> 
>  static inline struct drm_plane *drm_plane_find(struct drm_device *dev,

Krzysztof Kozlowski May 11, 2016, 11:56 a.m. UTC | #2

On 05/11/2016 12:25 PM, Benjamin Gaignard wrote:
> This patch adds support for generic plane's zpos property property with
> well-defined semantics:
> - added zpos properties to plane and plane state structures
> - added helpers for normalizing zpos properties of given set of planes
> - well defined semantics: planes are sorted by zpos values and then plane
>   id value if zpos equals
> 
> Normalized zpos values are calculated automatically when generic
> muttable zpos property has been initialized. Drivers can simply use
> plane_state->normalized_zpos in their atomic_check and/or plane_update
> callbacks without any additional calls to DRM core.
> 
> Signed-off-by: Marek Szyprowski <[e-mail]>
> 
> Compare to Marek's original patch zpos property is now specific to each
> plane and no more to the core.
> Normalize function take care of the range of per plane defined range
> before set normalized_zpos.
> 
> Signed-off-by: Benjamin Gaignard <[e-mail]>

The order of SoB is ok, but the "from" field should be set to Marek.

Best regards,
Krzysztof

Benjamin Gaignard May 11, 2016, 12:05 p.m. UTC | #3

Hi Laurent,


2016-05-11 13:24 GMT+02:00 Laurent Pinchart <[e-mail]>:
> Hi Benjamin,
>
> Thank you for the patch.
>
> I would have started working on this next week, thanks for beating me to it
> :-)
>
> On Wednesday 11 May 2016 12:25:05 Benjamin Gaignard wrote:
>> This patch adds support for generic plane's zpos property property with
>> well-defined semantics:
>> - added zpos properties to plane and plane state structures
>> - added helpers for normalizing zpos properties of given set of planes
>> - well defined semantics: planes are sorted by zpos values and then plane
>>   id value if zpos equals
>>
>> Normalized zpos values are calculated automatically when generic
>> muttable zpos property has been initialized. Drivers can simply use
>> plane_state->normalized_zpos in their atomic_check and/or plane_update
>> callbacks without any additional calls to DRM core.
>>
>> Signed-off-by: Marek Szyprowski <[e-mail]>
>>
>> Compare to Marek's original patch zpos property is now specific to each
>> plane and no more to the core.
>> Normalize function take care of the range of per plane defined range
>> before set normalized_zpos.
>>
>> Signed-off-by: Benjamin Gaignard <[e-mail]>
>>
>> Cc: Inki Dae <[e-mail]>
>> Cc: Daniel Vetter <[e-mail]>
>> Cc: Ville Syrjala <[e-mail]>
>> Cc: Joonyoung Shim <[e-mail]>
>> Cc: Seung-Woo Kim <[e-mail]>
>> Cc: Andrzej Hajda <[e-mail]>
>> Cc: Krzysztof Kozlowski <[e-mail]>
>> Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
>> Cc: Tobias Jakobi <[e-mail]>
>> Cc: Gustavo Padovan <[e-mail]>
>> Cc: [e-mail]
>> Cc: [e-mail]
>> Cc: Laurent Pinchart <[e-mail]>
>>
>> ---
>>  Documentation/DocBook/gpu.tmpl      |  10 ++
>>  drivers/gpu/drm/Makefile            |   2 +-
>>  drivers/gpu/drm/drm_atomic_helper.c |   6 +
>>  drivers/gpu/drm/drm_blend.c         | 284 +++++++++++++++++++++++++++++++++
>>  drivers/gpu/drm/drm_crtc_internal.h |   3 +
>>  include/drm/drm_crtc.h              |  25 ++++
>>  6 files changed, 329 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/gpu/drm/drm_blend.c
>>
>> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
>> index 9dd48f7..0df6abb 100644
>> --- a/Documentation/DocBook/gpu.tmpl
>> +++ b/Documentation/DocBook/gpu.tmpl
>> @@ -2151,6 +2151,16 @@ void intel_crt_init(struct drm_device *dev)
>>               the underlying hardware).</td>
>>       </tr>
>>       <tr>
>> +     <td valign="top" > "zpos" </td>
>> +     <td valign="top" >RANGE</td>
>> +     <td valign="top" >Min= driver dependent, Max= driver dependent</td>
>> +     <td valign="top" >Plane</td>
>> +     <td valign="top" >Plane's 'z' position during blending operation (0 for
>> background, highest for frontmost).
>> +             If two planes assigned to same CRTC have equal zpos values, the plane
>> with higher plane
>> +             id is treated as closer to front. Can be IMMUTABLE if driver doesn't
>> support changing
>> +             planes' order. Exact value range is driver dependent.</td>
>> +     </tr>
>> +     <tr>
>>       <td rowspan="20" valign="top" >i915</td>
>>       <td rowspan="2" valign="top" >Generic</td>
>>       <td valign="top" >"Broadcast RGB"</td>
>> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
>> index 2bd3e5a..df88253 100644
>> --- a/drivers/gpu/drm/Makefile
>> +++ b/drivers/gpu/drm/Makefile
>> @@ -2,7 +2,7 @@
>>  # Makefile for the drm device driver.  This driver provides support for the
>> # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
>>
>> -drm-y       :=       drm_auth.o drm_bufs.o drm_cache.o \
>> +drm-y       :=       drm_auth.o drm_bufs.o drm_blend.o drm_cache.o \
>>               drm_context.o drm_dma.o \
>>               drm_fops.o drm_gem.o drm_ioctl.o drm_irq.o \
>>               drm_lock.o drm_memory.o drm_drv.o drm_vm.o \
>> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
>> b/drivers/gpu/drm/drm_atomic_helper.c index 997fd21..f10652f 100644
>> --- a/drivers/gpu/drm/drm_atomic_helper.c
>> +++ b/drivers/gpu/drm/drm_atomic_helper.c
>> @@ -32,6 +32,8 @@
>>  #include <drm/drm_atomic_helper.h>
>>  #include <linux/fence.h>
>>
>> +#include "drm_crtc_internal.h"
>
> drm_atomic_helper_normalize_zpos() is declared in <drm/drm_crtc.h>, why do you
> need to include drm_crtc_internal.h ?

drm_atomic_helper_normalize_zpos() is declared in drm_crtc_internal.h
not into <drm/drm_crtc.h>

>
>>  /**
>>   * DOC: overview
>>   *
>> @@ -587,6 +589,10 @@ drm_atomic_helper_check_planes(struct drm_device *dev,
>>       struct drm_plane_state *plane_state;
>>       int i, ret = 0;
>>
>> +     ret = drm_atomic_helper_normalize_zpos(dev, state);
>> +     if (ret)
>> +             return ret;
>> +
>>       for_each_plane_in_state(state, plane, plane_state, i) {
>>               const struct drm_plane_helper_funcs *funcs;
>>
>> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
>> new file mode 100644
>> index 0000000..7017715
>> --- /dev/null
>> +++ b/drivers/gpu/drm/drm_blend.c
>> @@ -0,0 +1,284 @@
>
> [snip]
>
>> +#include <linux/slab.h>
>> +#include <linux/sort.h>
>> +#include <linux/export.h>
>> +#include <drm/drmP.h>
>> +#include <drm/drm_crtc.h>
>> +#include <drm/drm_atomic.h>
>
> Nitpicking, could you please keep header files alphabetically sorted ? It
> helps locating and avoiding duplicates.
>

sure, I will for v2

>> +#include "drm_internal.h"
>> +
>> +#define MAX(a, b) (((a) > (b)) ? (a) : (b))
>
> linux/kernel.h has max and max_t, is there really a need for a new macro ?

ok I will replace by max_t

>
>> +/**
>> + * drm_plane_atomic_set_zpos_property - set plane zpos property
>> + * @plane: drm plane
>> + * @state: drm plane state
>> + * @property: must be the zpos property associated to the plane
>> + * @val: zpos value to be set
>> + *
>> + * Returns:
>> + * Zero on success, negative errno on failure.
>> + */
>> +int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
>> +                                    struct drm_plane_state *state,
>> +                                    struct drm_property *property,
>> +                                    uint64_t val)
>> +{
>> +     struct drm_mode_object *obj = &plane->base;
>> +     int i;
>> +
>> +     for (i = 0; i < obj->properties->count; i++) {
>> +             if (obj->properties->properties[i] == property) {
>> +                     state->zpos = val;
>> +                     return 0;
>> +             }
>> +     }
>> +
>> +     return -EINVAL;
>> +}
>> +EXPORT_SYMBOL(drm_plane_atomic_set_zpos_property);
>
> Why do you need this function instead of adding zpos support to
> drm_atomic_plane_set_property() ? Same question for the get handler.
>
>> +/**
>> + * drm_plane_atomic_get_zpos_property - set plane zpos property
>> + * @plane: drm plane
>> + * @state: drm plane state
>> + * @property: must be the zpos property associated to the plane
>> + * @val: zpos value to be retrieve
>> + *
>> + * Returns:
>> + * Zero on success, negative errno on failure.
>> + */
>> +int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
>> +                                    const struct drm_plane_state *state,
>> +                                    struct drm_property *property,
>> +                                    uint64_t *val)
>> +{
>> +     struct drm_mode_object *obj = &plane->base;
>> +     int i;
>> +
>> +     for (i = 0; i < obj->properties->count; i++) {
>> +             if (obj->properties->properties[i] == property) {
>> +                     *val = state->zpos;
>> +                     return 0;
>> +             }
>> +     }
>> +
>> +     return -EINVAL;
>> +}
>> +EXPORT_SYMBOL(drm_plane_atomic_get_zpos_property);
>> +
>> +/**
>> + * drm_plane_create_zpos_property - create mutable zpos property
>> + * @plane: drm plane
>> + * @min: minimal possible value of zpos property
>> + * @max: maximal possible value of zpos property
>> + *
>> + * This function initializes generic mutable zpos property and enables
>> support
>> + * for it in drm core. Drivers can then attach this property to planes to
>> enable
>> + * support for configurable planes arrangement during blending operation.
>> + * Once mutable zpos property has been enabled, the DRM core will
>> automatically
>> + * calculate drm_plane_state->normalized_zpos values. Usually min should be
>> set
>> + * to 0 and max to maximal number of planes for given crtc - 1.
>> + *
>> + * If zpos of some planes cannot be changed (like fixed background or
>> + * cursor/topmost planes), driver should adjust min/max values and assign
>> those
>> + * planes immutable zpos property with lower or higher values (for more
>> + * information, see drm_mode_create_zpos_immutable_property() function). In
>> such
>> + * case driver should also assign proper initial zpos values for all planes
>> in
>> + * its plane_reset() callback, so the planes will be always sorted
>> properly.
>> + *
>> + * Returns:
>> + * Zero on success, negative errno on failure.
>> + */
>> +int drm_plane_create_zpos_property(struct drm_plane *plane,
>> +                                unsigned int min, unsigned int max)
>> +{
>> +     struct drm_property *prop;
>> +
>> +     prop = drm_property_create_range(plane->dev, 0, "zpos", min, max);
>> +     if (!prop)
>> +             return -ENOMEM;
>> +
>
> You should cache prop (in drm_mode_config) instead of recreating it for each
> plane, like done for the other properties. Same in the next function.
>
>> +     drm_object_attach_property(&plane->base, prop, min);
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL(drm_plane_create_zpos_property);
>> +
>> +/**
>> + * drm_plane_create_zpos_immutable_property - create immuttable zpos
>> property
>> + * @plane: drm plane
>> + * @min: minimal possible value of zpos property
>> + * @max: maximal possible value of zpos property
>> + *
>> + * This function initializes generic immutable zpos property and enables
>> + * support for it in drm core. Using this property driver lets userspace
>> + * to get the arrangement of the planes for blending operation and notifies
>> + * it that the hardware (or driver) doesn't support changing of the
>> planes'
>> + * order.
>> + *
>> + * Returns:
>> + * Zero on success, negative errno on failure.
>> + */
>> +int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
>> +                                          unsigned int min, unsigned int max)
>> +{
>> +     struct drm_property *prop;
>> +
>> +     prop = drm_property_create_range(plane->dev, DRM_MODE_PROP_IMMUTABLE,
>> +                                      "zpos", min, max);
>
> Can two properties exist with the same name but different flags (immutable and
> mutable) ? Or with different min/max values ? I don't expect min/max to be
> different for every plane, so maybe a function that creates the zpos property
> once with min/max values and a second one that attaches the property to planes
> would be a better API.
>

Be able to have a per plane zpos property was a Ville request because
all the planes may not have the same min/max zpos.
The consequences of this design are that we can cache the property in
drm_mode_config
and we need to have helpers functions
drm_plane_atomic_{set,get}_zpos_property to be able find
the property attached to the drm_plane.

>> +     if (!prop)
>> +             return -ENOMEM;
>> +
>> +     drm_object_attach_property(&plane->base, prop, min);
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL(drm_plane_create_zpos_immutable_property);
>> +
>> +static int drm_atomic_state_zpos_cmp(const void *a, const void *b)
>> +{
>> +     const struct drm_plane_state *sa = *(struct drm_plane_state **)a;
>> +     const struct drm_plane_state *sb = *(struct drm_plane_state **)b;
>> +     int zpos_a = (sa->zpos << 16) + sa->plane->base.id;
>> +     int zpos_b = (sb->zpos << 16) + sb->plane->base.id;
>> +
>> +     return zpos_a - zpos_b;
>
> Instead of playing tricks with the ids that will create a dependency on the
> plane id value range, how about
>
>         if (sa->zpos != sb->zpos)
>                 return sa->zpos - sb->zpos;
>         else
>                 return sa->plane->base.id - sb->plane->base.id;
>

It is how Marek have code it but you solution is more readable.

>> +}
>> +
>> +/**
>> + * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos values
>> + * @crtc: crtc with planes, which have to be considered for normalization
>> + * @crtc_state: new atomic state to apply
>> + *
>> + * This function checks new states of all planes assigned to given crtc and
>> + * calculates normalized zpos value for them. Planes are compared first by
>> their
>> + * zpos values, then by plane id (if zpos equals). Plane with lowest zpos
>> value
>> + * is at the bottom. The plane_state->normalized_zpos is then filled with
>> unique
>> + * values from 0 to number of active planes in crtc minus one.
>> + *
>> + * RETURNS
>> + * Zero for success or -errno
>> + */
>> +int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
>> +                                       struct drm_crtc_state *crtc_state)
>> +{
>> +     struct drm_atomic_state *state = crtc_state->state;
>> +     struct drm_device *dev = crtc->dev;
>> +     int total_planes = dev->mode_config.num_total_plane;
>> +     struct drm_plane_state **states;
>> +     struct drm_plane *plane;
>> +     int i, zpos, n = 0;
>> +     int ret = 0;
>> +
>> +     DRM_DEBUG_ATOMIC("[CRTC:%d:%s] calculating normalized zpos values\n",
>> +                      crtc->base.id, crtc->name);
>> +
>> +     states = kmalloc(total_planes * sizeof(*states), GFP_KERNEL);
>> +     if (!states)
>> +             return -ENOMEM;
>> +
>> +     /*
>> +      * Normalization process might create new states for planes which
>> +      * normalized_zpos has to be recalculated.
>> +      */
>> +     drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
>> +             struct drm_plane_state *plane_state =
>> +                     drm_atomic_get_plane_state(state, plane);
>> +             if (IS_ERR(plane_state)) {
>> +                     ret = PTR_ERR(plane_state);
>> +                     goto fail;
>> +             }
>> +             states[n++] = plane_state;
>> +             DRM_DEBUG_ATOMIC("[PLANE:%d:%s] processing zpos value %d\n",
>> +                              plane->base.id, plane->name,
>> +                              plane_state->zpos);
>> +     }
>> +
>> +     sort(states, n, sizeof(*states), drm_atomic_state_zpos_cmp, NULL);
>> +
>> +     for (i = 0, zpos = 0; i < n; i++, zpos++) {
>> +             plane = states[i]->plane;
>> +
>> +             zpos = MAX(zpos, states[i]->zpos);
>> +
>> +             states[i]->normalized_zpos = zpos;
>
> Can't you just use i instead of MAX(zpos, states[i]->zpos) ?

No because since each plane could have different min/max you could
have gaps between two plane.
For example if planeX range is [0,2] and planeY range is [4,6] we need
to be sure the min value of planeY is 4

>
>> +             DRM_DEBUG_ATOMIC("[PLANE:%d:%s] normalized zpos value %d\n",
>> +                              plane->base.id, plane->name, zpos);
>> +     }
>> +     crtc_state->zpos_changed = true;
>> +
>> +fail:
>
> We reach the label in the normal code path too, I would thus call it done or
> exit instead of fail.

I will change it to done

>
>> +     kfree(states);
>> +     return ret;
>> +}
>> +EXPORT_SYMBOL(drm_atomic_helper_crtc_normalize_zpos);
>> +
>> +/**
>> + * drm_atomic_helper_normalize_zpos - calculate normalized zpos values for
>> all
>> + *                                 crtcs
>> + * @dev: DRM device
>> + * @state: atomic state of DRM device
>> + *
>> + * This function calculates normalized zpos value for all modified planes
>> in
>> + * the provided atomic state of DRM device. For more information, see
>> + * drm_atomic_helper_crtc_normalize_zpos() function.
>> + *
>> + * RETURNS
>> + * Zero for success or -errno
>> + */
>> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
>> +                                  struct drm_atomic_state *state)
>> +{
>> +     struct drm_crtc *crtc;
>> +     struct drm_crtc_state *crtc_state;
>> +     struct drm_plane *plane;
>> +     struct drm_plane_state *plane_state;
>> +     int i, ret = 0;
>> +
>> +     for_each_plane_in_state(state, plane, plane_state, i) {
>> +             crtc = plane_state->crtc;
>> +             if (!crtc)
>> +                     continue;
>> +             if (plane->state->zpos != plane_state->zpos) {
>> +                     crtc_state =
>> +                             drm_atomic_get_existing_crtc_state(state, crtc);
>> +                     crtc_state->zpos_changed = true;
>> +             }
>> +     }
>> +
>> +     for_each_crtc_in_state(state, crtc, crtc_state, i) {
>> +             if (crtc_state->plane_mask != crtc->state->plane_mask ||
>> +                 crtc_state->zpos_changed) {
>> +                     ret = drm_atomic_helper_crtc_normalize_zpos(crtc,
>> +                                                                 crtc_state);
>> +                     if (ret)
>> +                             return ret;
>> +             }
>> +     }
>> +     return 0;
>> +}
>> +EXPORT_SYMBOL(drm_atomic_helper_normalize_zpos);
>> diff --git a/drivers/gpu/drm/drm_crtc_internal.h
>> b/drivers/gpu/drm/drm_crtc_internal.h index a78c138..37d9068 100644
>> --- a/drivers/gpu/drm/drm_crtc_internal.h
>> +++ b/drivers/gpu/drm/drm_crtc_internal.h
>> @@ -42,3 +42,6 @@ int drm_atomic_get_property(struct drm_mode_object *obj,
>>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>>                         void *data, struct drm_file *file_priv);
>>
>> +/* drm_blend.c */
>> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
>> +                                  struct drm_atomic_state *state);
>> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
>> index d1559cd..a34bc29 100644
>> --- a/include/drm/drm_crtc.h
>> +++ b/include/drm/drm_crtc.h
>> @@ -305,6 +305,7 @@ struct drm_plane_helper_funcs;
>>   * @mode_changed: crtc_state->mode or crtc_state->enable has been changed
>>   * @active_changed: crtc_state->active has been toggled.
>>   * @connectors_changed: connectors to this crtc have been updated
>> + * @zpos_changed: zpos values of planes on this crtc have been updated
>>   * @color_mgmt_changed: color management properties have changed (degamma
>> or *  gamma LUT or CSC matrix)
>>   * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
>> @@ -340,6 +341,7 @@ struct drm_crtc_state {
>>       bool mode_changed : 1;
>>       bool active_changed : 1;
>>       bool connectors_changed : 1;
>> +     bool zpos_changed : 1;
>>       bool color_mgmt_changed : 1;
>>
>>       /* attached planes bitmask:
>> @@ -1263,6 +1265,9 @@ struct drm_connector {
>>   *   plane (in 16.16)
>>   * @src_w: width of visible portion of plane (in 16.16)
>>   * @src_h: height of visible portion of plane (in 16.16)
>> + * @zpos: priority of the given plane on crtc (optional)
>> + * @normalized_zpos: normalized value of zpos: unique, range from 0 to N
>> + *    for given crtc
>
> If N is the number of active planes that would be 0 to N-1. If N is the number
> of active planes minus one then this is correct :-)

I will fix that.

>
>>   * @state: backpointer to global drm_atomic_state
>>   */
>>  struct drm_plane_state {
>> @@ -1283,6 +1288,10 @@ struct drm_plane_state {
>>       /* Plane rotation */
>>       unsigned int rotation;
>>
>> +     /* Plane zpos */
>> +     unsigned int zpos;
>> +     unsigned int normalized_zpos;
>> +
>>       struct drm_atomic_state *state;
>>  };
>>
>> @@ -2554,6 +2563,22 @@ extern struct drm_property
>> *drm_mode_create_rotation_property(struct drm_device extern unsigned int
>> drm_rotation_simplify(unsigned int rotation,
>>                                         unsigned int supported_rotations);
>>
>> +extern int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
>> +                                           struct drm_plane_state *state,
>> +                                           struct drm_property *property,
>> +                                           uint64_t val);
>> +
>
> You can drop the extern keywords, they're not needed. I know that lots of
> functions in this header file use extern, but not all of them do, and moving
> forward I don't see a big reason to keep using unneeded keywords.
>

ok done

>> +extern int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
>> +                                           const struct drm_plane_state *state,
>> +                                           struct drm_property *property,
>> +                                           uint64_t *val);
>> +
>> +extern int drm_plane_create_zpos_property(struct drm_plane *plane,
>> +                                       unsigned int min, unsigned int max);
>
> Shouldn't this be named drm_plane_attach_zpos_property() instead ? The main
> purpose of the function is to attach the property, even if it has to create it
> on first invocation as a side effect.
>
>> +extern int drm_plane_create_zpos_immutable_property(struct drm_plane
>> *plane,
>> +                                                 unsigned int min,
>> +                                                 unsigned int max);
>> +
>>  /* Helpers */
>>
>>  static inline struct drm_plane *drm_plane_find(struct drm_device *dev,
>
> --
> Regards,
>
> Laurent Pinchart
>

Laurent Pinchart May 11, 2016, 1:02 p.m. UTC | #4

Hi Benjamin,

On Wednesday 11 May 2016 14:05:49 Benjamin Gaignard wrote:
> 2016-05-11 13:24 GMT+02:00 Laurent Pinchart:
> > On Wednesday 11 May 2016 12:25:05 Benjamin Gaignard wrote:
> >> This patch adds support for generic plane's zpos property property with
> >> well-defined semantics:
> >> - added zpos properties to plane and plane state structures
> >> - added helpers for normalizing zpos properties of given set of planes
> >> - well defined semantics: planes are sorted by zpos values and then plane
> >>   id value if zpos equals
> >> 
> >> Normalized zpos values are calculated automatically when generic
> >> muttable zpos property has been initialized. Drivers can simply use
> >> plane_state->normalized_zpos in their atomic_check and/or plane_update
> >> callbacks without any additional calls to DRM core.
> >> 
> >> Signed-off-by: Marek Szyprowski <[e-mail]>
> >> 
> >> Compare to Marek's original patch zpos property is now specific to each
> >> plane and no more to the core.
> >> Normalize function take care of the range of per plane defined range
> >> before set normalized_zpos.
> >> 
> >> Signed-off-by: Benjamin Gaignard <[e-mail]>
> >> 
> >> Cc: Inki Dae <[e-mail]>
> >> Cc: Daniel Vetter <[e-mail]>
> >> Cc: Ville Syrjala <[e-mail]>
> >> Cc: Joonyoung Shim <[e-mail]>
> >> Cc: Seung-Woo Kim <[e-mail]>
> >> Cc: Andrzej Hajda <[e-mail]>
> >> Cc: Krzysztof Kozlowski <[e-mail]>
> >> Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
> >> Cc: Tobias Jakobi <[e-mail]>
> >> Cc: Gustavo Padovan <[e-mail]>
> >> Cc: [e-mail]
> >> Cc: [e-mail]
> >> Cc: Laurent Pinchart <[e-mail]>
> >> 
> >> ---
> >> 
> >>  Documentation/DocBook/gpu.tmpl      |  10 ++
> >>  drivers/gpu/drm/Makefile            |   2 +-
> >>  drivers/gpu/drm/drm_atomic_helper.c |   6 +
> >>  drivers/gpu/drm/drm_blend.c         | 284 ++++++++++++++++++++++++++++++
> >>  drivers/gpu/drm/drm_crtc_internal.h |   3 +
> >>  include/drm/drm_crtc.h              |  25 ++++
> >>  6 files changed, 329 insertions(+), 1 deletion(-)
> >>  create mode 100644 drivers/gpu/drm/drm_blend.c

[snip]

> >> diff --git a/drivers/gpu/drm/drm_atomic_helper.c
> >> b/drivers/gpu/drm/drm_atomic_helper.c index 997fd21..f10652f 100644
> >> --- a/drivers/gpu/drm/drm_atomic_helper.c
> >> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> >> @@ -32,6 +32,8 @@
> >> 
> >>  #include <drm/drm_atomic_helper.h>
> >>  #include <linux/fence.h>
> >> 
> >> +#include "drm_crtc_internal.h"
> > 
> > drm_atomic_helper_normalize_zpos() is declared in <drm/drm_crtc.h>, why do
> > you need to include drm_crtc_internal.h ?
> 
> drm_atomic_helper_normalize_zpos() is declared in drm_crtc_internal.h
> not into <drm/drm_crtc.h>

OK, I'll go back to bed -_-'

[snip]

> >> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> >> new file mode 100644
> >> index 0000000..7017715
> >> --- /dev/null
> >> +++ b/drivers/gpu/drm/drm_blend.c
> >> @@ -0,0 +1,284 @@

[snip]

> >> +/**
> >> + * drm_plane_create_zpos_immutable_property - create immuttable zpos
> >> property
> >> + * @plane: drm plane
> >> + * @min: minimal possible value of zpos property
> >> + * @max: maximal possible value of zpos property
> >> + *
> >> + * This function initializes generic immutable zpos property and enables
> >> + * support for it in drm core. Using this property driver lets userspace
> >> + * to get the arrangement of the planes for blending operation and
> >> notifies + * it that the hardware (or driver) doesn't support changing
> >> of the planes'
> >> + * order.
> >> + *
> >> + * Returns:
> >> + * Zero on success, negative errno on failure.
> >> + */
> >> +int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
> >> +                                          unsigned int min, unsigned int
> >> max) +{
> >> +     struct drm_property *prop;
> >> +
> >> +     prop = drm_property_create_range(plane->dev,
> >> DRM_MODE_PROP_IMMUTABLE,
> >> +                                      "zpos", min, max);
> > 
> > Can two properties exist with the same name but different flags (immutable
> > and mutable) ? Or with different min/max values ? I don't expect min/max
> > to be different for every plane, so maybe a function that creates the
> > zpos property once with min/max values and a second one that attaches the
> > property to planes would be a better API.
> 
> Be able to have a per plane zpos property was a Ville request because
> all the planes may not have the same min/max zpos.

Which driver(s) need that feature ? Is it for the cursor plane only ? In that 
case I wonder if it would really make sense to create an immutable zpos 
property with a fixed high value for the cursor plane, versus not having a 
zpos property at all.

> The consequences of this design are that we can cache the property in
> drm_mode_config
> and we need to have helpers functions
> drm_plane_atomic_{set,get}_zpos_property to be able find
> the property attached to the drm_plane.

Can't you cache it in drm_plane instead then, and remove the loop from those 
two helpers ? You should even remove the helpers completely and handle the 
zpos property in drm_plane_atomic_[gs]et_property().

> >> +     if (!prop)
> >> +             return -ENOMEM;
> >> +
> >> +     drm_object_attach_property(&plane->base, prop, min);
> >> +     return 0;
> >> +}
> >> +EXPORT_SYMBOL(drm_plane_create_zpos_immutable_property);

[snip]

> >> +/**
> >> + * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos
> >> values
> >> + * @crtc: crtc with planes, which have to be considered for
> >> normalization
> >> + * @crtc_state: new atomic state to apply
> >> + *
> >> + * This function checks new states of all planes assigned to given crtc
> >> and
> >> + * calculates normalized zpos value for them. Planes are compared first
> >> by their
> >> + * zpos values, then by plane id (if zpos equals). Plane with lowest
> >> zpos value
> >> + * is at the bottom. The plane_state->normalized_zpos is then filled
> >> with unique
> >> + * values from 0 to number of active planes in crtc minus one.
> >> + *
> >> + * RETURNS
> >> + * Zero for success or -errno
> >> + */
> >> +int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
> >> +                                       struct drm_crtc_state
> >> *crtc_state)
> >> +{
> >> +     struct drm_atomic_state *state = crtc_state->state;
> >> +     struct drm_device *dev = crtc->dev;
> >> +     int total_planes = dev->mode_config.num_total_plane;
> >> +     struct drm_plane_state **states;
> >> +     struct drm_plane *plane;
> >> +     int i, zpos, n = 0;
> >> +     int ret = 0;
> >> +
> >> +     DRM_DEBUG_ATOMIC("[CRTC:%d:%s] calculating normalized zpos
> >> values\n",
> >> +                      crtc->base.id, crtc->name);
> >> +
> >> +     states = kmalloc(total_planes * sizeof(*states), GFP_KERNEL);
> >> +     if (!states)
> >> +             return -ENOMEM;
> >> +
> >> +     /*
> >> +      * Normalization process might create new states for planes which
> >> +      * normalized_zpos has to be recalculated.
> >> +      */
> >> +     drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
> >> +             struct drm_plane_state *plane_state =
> >> +                     drm_atomic_get_plane_state(state, plane);
> >> +             if (IS_ERR(plane_state)) {
> >> +                     ret = PTR_ERR(plane_state);
> >> +                     goto fail;
> >> +             }
> >> +             states[n++] = plane_state;
> >> +             DRM_DEBUG_ATOMIC("[PLANE:%d:%s] processing zpos value
> >> %d\n",
> >> +                              plane->base.id, plane->name,
> >> +                              plane_state->zpos);
> >> +     }
> >> +
> >> +     sort(states, n, sizeof(*states), drm_atomic_state_zpos_cmp, NULL);
> >> +
> >> +     for (i = 0, zpos = 0; i < n; i++, zpos++) {
> >> +             plane = states[i]->plane;
> >> +
> >> +             zpos = MAX(zpos, states[i]->zpos);
> >> +
> >> +             states[i]->normalized_zpos = zpos;
> > 
> > Can't you just use i instead of MAX(zpos, states[i]->zpos) ?
> 
> No because since each plane could have different min/max you could
> have gaps between two plane.
> For example if planeX range is [0,2] and planeY range is [4,6] we need
> to be sure the min value of planeY is 4

And that's exactly what I'd rather avoid. I think the core code should take 
care of sorting planes, taking driver-specific constraints into account when 
possible (too exotic constraints can always be implemented directly by 
drivers), and then leave to the drivers the responsibility of taking the 
sorted planes array and computing whatever hardware-specific configuration is 
needed. Sorting planes from 0 to N-1 seems to be like a better API than having 
semi-random values for the normalized zpos.

Do we even have a real use case for the "feature" you described ?

> >> +             DRM_DEBUG_ATOMIC("[PLANE:%d:%s] normalized zpos value
> >> %d\n",
> >> +                              plane->base.id, plane->name, zpos);
> >> +     }
> >> +     crtc_state->zpos_changed = true;
> >> +
> > 
> >> +fail:
> > We reach the label in the normal code path too, I would thus call it done
> > or exit instead of fail.
> 
> I will change it to done
> 
> >> +     kfree(states);
> >> +     return ret;
> >> +}
> >> +EXPORT_SYMBOL(drm_atomic_helper_crtc_normalize_zpos);

[snip]

Daniel Vetter May 11, 2016, 1:21 p.m. UTC | #5

On Wed, May 11, 2016 at 12:25:05PM +0200, Benjamin Gaignard wrote:
> This patch adds support for generic plane's zpos property property with
> well-defined semantics:
> - added zpos properties to plane and plane state structures
> - added helpers for normalizing zpos properties of given set of planes
> - well defined semantics: planes are sorted by zpos values and then plane
>   id value if zpos equals
> 
> Normalized zpos values are calculated automatically when generic
> muttable zpos property has been initialized. Drivers can simply use
> plane_state->normalized_zpos in their atomic_check and/or plane_update
> callbacks without any additional calls to DRM core.
> 
> Signed-off-by: Marek Szyprowski <[e-mail]>
> 
> Compare to Marek's original patch zpos property is now specific to each
> plane and no more to the core.
> Normalize function take care of the range of per plane defined range
> before set normalized_zpos.
> 
> Signed-off-by: Benjamin Gaignard <[e-mail]>
> 
> Cc: Inki Dae <[e-mail]>
> Cc: Daniel Vetter <[e-mail]>
> Cc: Ville Syrjala <[e-mail]>
> Cc: Joonyoung Shim <[e-mail]>
> Cc: Seung-Woo Kim <[e-mail]>
> Cc: Andrzej Hajda <[e-mail]>
> Cc: Krzysztof Kozlowski <[e-mail]>
> Cc: Bartlomiej Zolnierkiewicz <[e-mail]>
> Cc: Tobias Jakobi <[e-mail]>
> Cc: Gustavo Padovan <[e-mail]>
> Cc: [e-mail]
> Cc: [e-mail]
> Cc: Laurent Pinchart <[e-mail]>
> 
> ---
>  Documentation/DocBook/gpu.tmpl      |  10 ++
>  drivers/gpu/drm/Makefile            |   2 +-
>  drivers/gpu/drm/drm_atomic_helper.c |   6 +
>  drivers/gpu/drm/drm_blend.c         | 284 ++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/drm_crtc_internal.h |   3 +
>  include/drm/drm_crtc.h              |  25 ++++
>  6 files changed, 329 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/gpu/drm/drm_blend.c
> 
> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> index 9dd48f7..0df6abb 100644
> --- a/Documentation/DocBook/gpu.tmpl
> +++ b/Documentation/DocBook/gpu.tmpl
> @@ -2151,6 +2151,16 @@ void intel_crt_init(struct drm_device *dev)
>  		the underlying hardware).</td>
>  	</tr>
>  	<tr>
> +	<td valign="top" > "zpos" </td>
> +	<td valign="top" >RANGE</td>
> +	<td valign="top" >Min= driver dependent, Max= driver dependent</td>
> +	<td valign="top" >Plane</td>
> +	<td valign="top" >Plane's 'z' position during blending operation (0 for background, highest for frontmost).
> +		If two planes assigned to same CRTC have equal zpos values, the plane with higher plane
> +		id is treated as closer to front. Can be IMMUTABLE if driver doesn't support changing
> +		planes' order. Exact value range is driver dependent.</td>
> +	</tr>
> +	<tr>
>  	<td rowspan="20" valign="top" >i915</td>
>  	<td rowspan="2" valign="top" >Generic</td>
>  	<td valign="top" >"Broadcast RGB"</td>
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 2bd3e5a..df88253 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -2,7 +2,7 @@
>  # Makefile for the drm device driver.  This driver provides support for the
>  # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
>  
> -drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
> +drm-y       :=	drm_auth.o drm_bufs.o drm_blend.o drm_cache.o \
>  		drm_context.o drm_dma.o \
>  		drm_fops.o drm_gem.o drm_ioctl.o drm_irq.o \
>  		drm_lock.o drm_memory.o drm_drv.o drm_vm.o \
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 997fd21..f10652f 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -32,6 +32,8 @@
>  #include <drm/drm_atomic_helper.h>
>  #include <linux/fence.h>
>  
> +#include "drm_crtc_internal.h"
> +
>  /**
>   * DOC: overview
>   *
> @@ -587,6 +589,10 @@ drm_atomic_helper_check_planes(struct drm_device *dev,
>  	struct drm_plane_state *plane_state;
>  	int i, ret = 0;
>  
> +	ret = drm_atomic_helper_normalize_zpos(dev, state);
> +	if (ret)
> +		return ret;
> +
>  	for_each_plane_in_state(state, plane, plane_state, i) {
>  		const struct drm_plane_helper_funcs *funcs;
>  
> diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
> new file mode 100644
> index 0000000..7017715
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_blend.c
> @@ -0,0 +1,284 @@
> +/*
> + * Copyright (C) 2016 Samsung Electronics Co.Ltd
> + * Authors:
> + *	Marek Szyprowski <[e-mail]>
> + *
> + * DRM core plane blending related functions
> + *
> + * Permission to use, copy, modify, distribute, and sell this software and its
> + * documentation for any purpose is hereby granted without fee, provided that
> + * the above copyright notice appear in all copies and that both that copyright
> + * notice and this permission notice appear in supporting documentation, and
> + * that the name of the copyright holders not be used in advertising or
> + * publicity pertaining to distribution of the software without specific,
> + * written prior permission.  The copyright holders make no representations
> + * about the suitability of this software for any purpose.  It is provided "as
> + * is" without express or implied warranty.
> + *
> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
> + * OF THIS SOFTWARE.
> + */
> +#include <linux/slab.h>
> +#include <linux/sort.h>
> +#include <linux/export.h>
> +#include <drm/drmP.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_atomic.h>
> +
> +#include "drm_internal.h"
> +
> +#define MAX(a, b) (((a) > (b)) ? (a) : (b))
> +
> +/**
> + * drm_plane_atomic_set_zpos_property - set plane zpos property
> + * @plane: drm plane
> + * @state: drm plane state
> + * @property: must be the zpos property associated to the plane
> + * @val: zpos value to be set
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
> +				       struct drm_plane_state *state,
> +				       struct drm_property *property,
> +				       uint64_t val)
> +{
> +	struct drm_mode_object *obj = &plane->base;
> +	int i;
> +
> +	for (i = 0; i < obj->properties->count; i++) {
> +		if (obj->properties->properties[i] == property) {
> +			state->zpos = val;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(drm_plane_atomic_set_zpos_property);
> +
> +/**
> + * drm_plane_atomic_get_zpos_property - set plane zpos property
> + * @plane: drm plane
> + * @state: drm plane state
> + * @property: must be the zpos property associated to the plane
> + * @val: zpos value to be retrieve
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
> +				       const struct drm_plane_state *state,
> +				       struct drm_property *property,
> +				       uint64_t *val)
> +{
> +	struct drm_mode_object *obj = &plane->base;
> +	int i;
> +
> +	for (i = 0; i < obj->properties->count; i++) {
> +		if (obj->properties->properties[i] == property) {
> +			*val = state->zpos;
> +			return 0;
> +		}
> +	}
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(drm_plane_atomic_get_zpos_property);

For standardized functions we don't want drivers to do the decoding, even
if it's only done by calling into an exported function like the above two.

Instead the decoding should be done in the drm core in
drm_atomic_plane_set_property and drm_atomic_plane_get_property. That
requires though that the zpos property itself is registered at a place the
core can get at, i.e. we need to add drm_plane->zpos_prop pointer.

See for example how rotation is handled, the only difference is that
currently there's only one global rotation property, whereas with planes
we want it to be per-plane.

The benefit is both more incentives to use the standardized properties,
and less boilerplate in drivers (since they can just access state->zpos
without taking any action above registering/attaching the zpos prop to a
plane).

> +
> +/**
> + * drm_plane_create_zpos_property - create mutable zpos property
> + * @plane: drm plane
> + * @min: minimal possible value of zpos property
> + * @max: maximal possible value of zpos property
> + *
> + * This function initializes generic mutable zpos property and enables support
> + * for it in drm core. Drivers can then attach this property to planes to enable
> + * support for configurable planes arrangement during blending operation.
> + * Once mutable zpos property has been enabled, the DRM core will automatically
> + * calculate drm_plane_state->normalized_zpos values. Usually min should be set
> + * to 0 and max to maximal number of planes for given crtc - 1.
> + *
> + * If zpos of some planes cannot be changed (like fixed background or
> + * cursor/topmost planes), driver should adjust min/max values and assign those
> + * planes immutable zpos property with lower or higher values (for more
> + * information, see drm_mode_create_zpos_immutable_property() function). In such
> + * case driver should also assign proper initial zpos values for all planes in
> + * its plane_reset() callback, so the planes will be always sorted properly.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_create_zpos_property(struct drm_plane *plane,
> +				   unsigned int min, unsigned int max)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create_range(plane->dev, 0, "zpos", min, max);
> +	if (!prop)
> +		return -ENOMEM;
> +

See above, but we need to store the prop in plane->zpos_prop.
-Daniel

> +	drm_object_attach_property(&plane->base, prop, min);
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_create_zpos_property);
> +
> +/**
> + * drm_plane_create_zpos_immutable_property - create immuttable zpos property
> + * @plane: drm plane
> + * @min: minimal possible value of zpos property
> + * @max: maximal possible value of zpos property
> + *
> + * This function initializes generic immutable zpos property and enables
> + * support for it in drm core. Using this property driver lets userspace
> + * to get the arrangement of the planes for blending operation and notifies
> + * it that the hardware (or driver) doesn't support changing of the planes'
> + * order.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
> +					     unsigned int min, unsigned int max)
> +{
> +	struct drm_property *prop;
> +
> +	prop = drm_property_create_range(plane->dev, DRM_MODE_PROP_IMMUTABLE,
> +					 "zpos", min, max);
> +	if (!prop)
> +		return -ENOMEM;
> +
> +	drm_object_attach_property(&plane->base, prop, min);
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_plane_create_zpos_immutable_property);
> +
> +static int drm_atomic_state_zpos_cmp(const void *a, const void *b)
> +{
> +	const struct drm_plane_state *sa = *(struct drm_plane_state **)a;
> +	const struct drm_plane_state *sb = *(struct drm_plane_state **)b;
> +	int zpos_a = (sa->zpos << 16) + sa->plane->base.id;
> +	int zpos_b = (sb->zpos << 16) + sb->plane->base.id;
> +
> +	return zpos_a - zpos_b;
> +}
> +
> +/**
> + * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos values
> + * @crtc: crtc with planes, which have to be considered for normalization
> + * @crtc_state: new atomic state to apply
> + *
> + * This function checks new states of all planes assigned to given crtc and
> + * calculates normalized zpos value for them. Planes are compared first by their
> + * zpos values, then by plane id (if zpos equals). Plane with lowest zpos value
> + * is at the bottom. The plane_state->normalized_zpos is then filled with unique
> + * values from 0 to number of active planes in crtc minus one.
> + *
> + * RETURNS
> + * Zero for success or -errno
> + */
> +int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
> +					  struct drm_crtc_state *crtc_state)
> +{
> +	struct drm_atomic_state *state = crtc_state->state;
> +	struct drm_device *dev = crtc->dev;
> +	int total_planes = dev->mode_config.num_total_plane;
> +	struct drm_plane_state **states;
> +	struct drm_plane *plane;
> +	int i, zpos, n = 0;
> +	int ret = 0;
> +
> +	DRM_DEBUG_ATOMIC("[CRTC:%d:%s] calculating normalized zpos values\n",
> +			 crtc->base.id, crtc->name);
> +
> +	states = kmalloc(total_planes * sizeof(*states), GFP_KERNEL);
> +	if (!states)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Normalization process might create new states for planes which
> +	 * normalized_zpos has to be recalculated.
> +	 */
> +	drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
> +		struct drm_plane_state *plane_state =
> +			drm_atomic_get_plane_state(state, plane);
> +		if (IS_ERR(plane_state)) {
> +			ret = PTR_ERR(plane_state);
> +			goto fail;
> +		}
> +		states[n++] = plane_state;
> +		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] processing zpos value %d\n",
> +				 plane->base.id, plane->name,
> +				 plane_state->zpos);
> +	}
> +
> +	sort(states, n, sizeof(*states), drm_atomic_state_zpos_cmp, NULL);
> +
> +	for (i = 0, zpos = 0; i < n; i++, zpos++) {
> +		plane = states[i]->plane;
> +
> +		zpos = MAX(zpos, states[i]->zpos);
> +
> +		states[i]->normalized_zpos = zpos;
> +		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] normalized zpos value %d\n",
> +				 plane->base.id, plane->name, zpos);
> +	}
> +	crtc_state->zpos_changed = true;
> +
> +fail:
> +	kfree(states);
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_crtc_normalize_zpos);
> +
> +/**
> + * drm_atomic_helper_normalize_zpos - calculate normalized zpos values for all
> + *				      crtcs
> + * @dev: DRM device
> + * @state: atomic state of DRM device
> + *
> + * This function calculates normalized zpos value for all modified planes in
> + * the provided atomic state of DRM device. For more information, see
> + * drm_atomic_helper_crtc_normalize_zpos() function.
> + *
> + * RETURNS
> + * Zero for success or -errno
> + */
> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
> +				     struct drm_atomic_state *state)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_plane *plane;
> +	struct drm_plane_state *plane_state;
> +	int i, ret = 0;
> +
> +	for_each_plane_in_state(state, plane, plane_state, i) {
> +		crtc = plane_state->crtc;
> +		if (!crtc)
> +			continue;
> +		if (plane->state->zpos != plane_state->zpos) {
> +			crtc_state =
> +				drm_atomic_get_existing_crtc_state(state, crtc);
> +			crtc_state->zpos_changed = true;
> +		}
> +	}
> +
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +		if (crtc_state->plane_mask != crtc->state->plane_mask ||
> +		    crtc_state->zpos_changed) {
> +			ret = drm_atomic_helper_crtc_normalize_zpos(crtc,
> +								    crtc_state);
> +			if (ret)
> +				return ret;
> +		}
> +	}
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_atomic_helper_normalize_zpos);
> diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
> index a78c138..37d9068 100644
> --- a/drivers/gpu/drm/drm_crtc_internal.h
> +++ b/drivers/gpu/drm/drm_crtc_internal.h
> @@ -42,3 +42,6 @@ int drm_atomic_get_property(struct drm_mode_object *obj,
>  int drm_mode_atomic_ioctl(struct drm_device *dev,
>  			  void *data, struct drm_file *file_priv);
>  
> +/* drm_blend.c */
> +int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
> +				     struct drm_atomic_state *state);
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index d1559cd..a34bc29 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -305,6 +305,7 @@ struct drm_plane_helper_funcs;
>   * @mode_changed: crtc_state->mode or crtc_state->enable has been changed
>   * @active_changed: crtc_state->active has been toggled.
>   * @connectors_changed: connectors to this crtc have been updated
> + * @zpos_changed: zpos values of planes on this crtc have been updated
>   * @color_mgmt_changed: color management properties have changed (degamma or
>   *	gamma LUT or CSC matrix)
>   * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
> @@ -340,6 +341,7 @@ struct drm_crtc_state {
>  	bool mode_changed : 1;
>  	bool active_changed : 1;
>  	bool connectors_changed : 1;
> +	bool zpos_changed : 1;
>  	bool color_mgmt_changed : 1;
>  
>  	/* attached planes bitmask:
> @@ -1263,6 +1265,9 @@ struct drm_connector {
>   *	plane (in 16.16)
>   * @src_w: width of visible portion of plane (in 16.16)
>   * @src_h: height of visible portion of plane (in 16.16)
> + * @zpos: priority of the given plane on crtc (optional)
> + * @normalized_zpos: normalized value of zpos: unique, range from 0 to N
> + *	 for given crtc
>   * @state: backpointer to global drm_atomic_state
>   */
>  struct drm_plane_state {
> @@ -1283,6 +1288,10 @@ struct drm_plane_state {
>  	/* Plane rotation */
>  	unsigned int rotation;
>  
> +	/* Plane zpos */
> +	unsigned int zpos;
> +	unsigned int normalized_zpos;
> +
>  	struct drm_atomic_state *state;
>  };
>  
> @@ -2554,6 +2563,22 @@ extern struct drm_property *drm_mode_create_rotation_property(struct drm_device
>  extern unsigned int drm_rotation_simplify(unsigned int rotation,
>  					  unsigned int supported_rotations);
>  
> +extern int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
> +					      struct drm_plane_state *state,
> +					      struct drm_property *property,
> +					      uint64_t val);
> +
> +extern int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
> +					      const struct drm_plane_state *state,
> +					      struct drm_property *property,
> +					      uint64_t *val);
> +
> +extern int drm_plane_create_zpos_property(struct drm_plane *plane,
> +					  unsigned int min, unsigned int max);
> +extern int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
> +						    unsigned int min,
> +						    unsigned int max);
> +
>  /* Helpers */
>  
>  static inline struct drm_plane *drm_plane_find(struct drm_device *dev,
> -- 
> 1.9.1
>

Patch

diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
index 9dd48f7..0df6abb 100644
--- a/Documentation/DocBook/gpu.tmpl
+++ b/Documentation/DocBook/gpu.tmpl
@@ -2151,6 +2151,16 @@  void intel_crt_init(struct drm_device *dev)
 		the underlying hardware).</td>
 	</tr>
 	<tr>
+	<td valign="top" > "zpos" </td>
+	<td valign="top" >RANGE</td>
+	<td valign="top" >Min= driver dependent, Max= driver dependent</td>
+	<td valign="top" >Plane</td>
+	<td valign="top" >Plane's 'z' position during blending operation (0 for background, highest for frontmost).
+		If two planes assigned to same CRTC have equal zpos values, the plane with higher plane
+		id is treated as closer to front. Can be IMMUTABLE if driver doesn't support changing
+		planes' order. Exact value range is driver dependent.</td>
+	</tr>
+	<tr>
 	<td rowspan="20" valign="top" >i915</td>
 	<td rowspan="2" valign="top" >Generic</td>
 	<td valign="top" >"Broadcast RGB"</td>
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 2bd3e5a..df88253 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -2,7 +2,7 @@ 
 # Makefile for the drm device driver.  This driver provides support for the
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
-drm-y       :=	drm_auth.o drm_bufs.o drm_cache.o \
+drm-y       :=	drm_auth.o drm_bufs.o drm_blend.o drm_cache.o \
 		drm_context.o drm_dma.o \
 		drm_fops.o drm_gem.o drm_ioctl.o drm_irq.o \
 		drm_lock.o drm_memory.o drm_drv.o drm_vm.o \
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 997fd21..f10652f 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -32,6 +32,8 @@ 
 #include <drm/drm_atomic_helper.h>
 #include <linux/fence.h>
 
+#include "drm_crtc_internal.h"
+
 /**
  * DOC: overview
  *
@@ -587,6 +589,10 @@  drm_atomic_helper_check_planes(struct drm_device *dev,
 	struct drm_plane_state *plane_state;
 	int i, ret = 0;
 
+	ret = drm_atomic_helper_normalize_zpos(dev, state);
+	if (ret)
+		return ret;
+
 	for_each_plane_in_state(state, plane, plane_state, i) {
 		const struct drm_plane_helper_funcs *funcs;
 
diff --git a/drivers/gpu/drm/drm_blend.c b/drivers/gpu/drm/drm_blend.c
new file mode 100644
index 0000000..7017715
--- /dev/null
+++ b/drivers/gpu/drm/drm_blend.c
@@ -0,0 +1,284 @@ 
+/*
+ * Copyright (C) 2016 Samsung Electronics Co.Ltd
+ * Authors:
+ *	Marek Szyprowski <[e-mail]>
+ *
+ * DRM core plane blending related functions
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/export.h>
+#include <drm/drmP.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_atomic.h>
+
+#include "drm_internal.h"
+
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+
+/**
+ * drm_plane_atomic_set_zpos_property - set plane zpos property
+ * @plane: drm plane
+ * @state: drm plane state
+ * @property: must be the zpos property associated to the plane
+ * @val: zpos value to be set
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
+				       struct drm_plane_state *state,
+				       struct drm_property *property,
+				       uint64_t val)
+{
+	struct drm_mode_object *obj = &plane->base;
+	int i;
+
+	for (i = 0; i < obj->properties->count; i++) {
+		if (obj->properties->properties[i] == property) {
+			state->zpos = val;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(drm_plane_atomic_set_zpos_property);
+
+/**
+ * drm_plane_atomic_get_zpos_property - set plane zpos property
+ * @plane: drm plane
+ * @state: drm plane state
+ * @property: must be the zpos property associated to the plane
+ * @val: zpos value to be retrieve
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
+				       const struct drm_plane_state *state,
+				       struct drm_property *property,
+				       uint64_t *val)
+{
+	struct drm_mode_object *obj = &plane->base;
+	int i;
+
+	for (i = 0; i < obj->properties->count; i++) {
+		if (obj->properties->properties[i] == property) {
+			*val = state->zpos;
+			return 0;
+		}
+	}
+
+	return -EINVAL;
+}
+EXPORT_SYMBOL(drm_plane_atomic_get_zpos_property);
+
+/**
+ * drm_plane_create_zpos_property - create mutable zpos property
+ * @plane: drm plane
+ * @min: minimal possible value of zpos property
+ * @max: maximal possible value of zpos property
+ *
+ * This function initializes generic mutable zpos property and enables support
+ * for it in drm core. Drivers can then attach this property to planes to enable
+ * support for configurable planes arrangement during blending operation.
+ * Once mutable zpos property has been enabled, the DRM core will automatically
+ * calculate drm_plane_state->normalized_zpos values. Usually min should be set
+ * to 0 and max to maximal number of planes for given crtc - 1.
+ *
+ * If zpos of some planes cannot be changed (like fixed background or
+ * cursor/topmost planes), driver should adjust min/max values and assign those
+ * planes immutable zpos property with lower or higher values (for more
+ * information, see drm_mode_create_zpos_immutable_property() function). In such
+ * case driver should also assign proper initial zpos values for all planes in
+ * its plane_reset() callback, so the planes will be always sorted properly.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_create_zpos_property(struct drm_plane *plane,
+				   unsigned int min, unsigned int max)
+{
+	struct drm_property *prop;
+
+	prop = drm_property_create_range(plane->dev, 0, "zpos", min, max);
+	if (!prop)
+		return -ENOMEM;
+
+	drm_object_attach_property(&plane->base, prop, min);
+	return 0;
+}
+EXPORT_SYMBOL(drm_plane_create_zpos_property);
+
+/**
+ * drm_plane_create_zpos_immutable_property - create immuttable zpos property
+ * @plane: drm plane
+ * @min: minimal possible value of zpos property
+ * @max: maximal possible value of zpos property
+ *
+ * This function initializes generic immutable zpos property and enables
+ * support for it in drm core. Using this property driver lets userspace
+ * to get the arrangement of the planes for blending operation and notifies
+ * it that the hardware (or driver) doesn't support changing of the planes'
+ * order.
+ *
+ * Returns:
+ * Zero on success, negative errno on failure.
+ */
+int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
+					     unsigned int min, unsigned int max)
+{
+	struct drm_property *prop;
+
+	prop = drm_property_create_range(plane->dev, DRM_MODE_PROP_IMMUTABLE,
+					 "zpos", min, max);
+	if (!prop)
+		return -ENOMEM;
+
+	drm_object_attach_property(&plane->base, prop, min);
+	return 0;
+}
+EXPORT_SYMBOL(drm_plane_create_zpos_immutable_property);
+
+static int drm_atomic_state_zpos_cmp(const void *a, const void *b)
+{
+	const struct drm_plane_state *sa = *(struct drm_plane_state **)a;
+	const struct drm_plane_state *sb = *(struct drm_plane_state **)b;
+	int zpos_a = (sa->zpos << 16) + sa->plane->base.id;
+	int zpos_b = (sb->zpos << 16) + sb->plane->base.id;
+
+	return zpos_a - zpos_b;
+}
+
+/**
+ * drm_atomic_helper_crtc_normalize_zpos - calculate normalized zpos values
+ * @crtc: crtc with planes, which have to be considered for normalization
+ * @crtc_state: new atomic state to apply
+ *
+ * This function checks new states of all planes assigned to given crtc and
+ * calculates normalized zpos value for them. Planes are compared first by their
+ * zpos values, then by plane id (if zpos equals). Plane with lowest zpos value
+ * is at the bottom. The plane_state->normalized_zpos is then filled with unique
+ * values from 0 to number of active planes in crtc minus one.
+ *
+ * RETURNS
+ * Zero for success or -errno
+ */
+int drm_atomic_helper_crtc_normalize_zpos(struct drm_crtc *crtc,
+					  struct drm_crtc_state *crtc_state)
+{
+	struct drm_atomic_state *state = crtc_state->state;
+	struct drm_device *dev = crtc->dev;
+	int total_planes = dev->mode_config.num_total_plane;
+	struct drm_plane_state **states;
+	struct drm_plane *plane;
+	int i, zpos, n = 0;
+	int ret = 0;
+
+	DRM_DEBUG_ATOMIC("[CRTC:%d:%s] calculating normalized zpos values\n",
+			 crtc->base.id, crtc->name);
+
+	states = kmalloc(total_planes * sizeof(*states), GFP_KERNEL);
+	if (!states)
+		return -ENOMEM;
+
+	/*
+	 * Normalization process might create new states for planes which
+	 * normalized_zpos has to be recalculated.
+	 */
+	drm_for_each_plane_mask(plane, dev, crtc_state->plane_mask) {
+		struct drm_plane_state *plane_state =
+			drm_atomic_get_plane_state(state, plane);
+		if (IS_ERR(plane_state)) {
+			ret = PTR_ERR(plane_state);
+			goto fail;
+		}
+		states[n++] = plane_state;
+		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] processing zpos value %d\n",
+				 plane->base.id, plane->name,
+				 plane_state->zpos);
+	}
+
+	sort(states, n, sizeof(*states), drm_atomic_state_zpos_cmp, NULL);
+
+	for (i = 0, zpos = 0; i < n; i++, zpos++) {
+		plane = states[i]->plane;
+
+		zpos = MAX(zpos, states[i]->zpos);
+
+		states[i]->normalized_zpos = zpos;
+		DRM_DEBUG_ATOMIC("[PLANE:%d:%s] normalized zpos value %d\n",
+				 plane->base.id, plane->name, zpos);
+	}
+	crtc_state->zpos_changed = true;
+
+fail:
+	kfree(states);
+	return ret;
+}
+EXPORT_SYMBOL(drm_atomic_helper_crtc_normalize_zpos);
+
+/**
+ * drm_atomic_helper_normalize_zpos - calculate normalized zpos values for all
+ *				      crtcs
+ * @dev: DRM device
+ * @state: atomic state of DRM device
+ *
+ * This function calculates normalized zpos value for all modified planes in
+ * the provided atomic state of DRM device. For more information, see
+ * drm_atomic_helper_crtc_normalize_zpos() function.
+ *
+ * RETURNS
+ * Zero for success or -errno
+ */
+int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
+				     struct drm_atomic_state *state)
+{
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	struct drm_plane *plane;
+	struct drm_plane_state *plane_state;
+	int i, ret = 0;
+
+	for_each_plane_in_state(state, plane, plane_state, i) {
+		crtc = plane_state->crtc;
+		if (!crtc)
+			continue;
+		if (plane->state->zpos != plane_state->zpos) {
+			crtc_state =
+				drm_atomic_get_existing_crtc_state(state, crtc);
+			crtc_state->zpos_changed = true;
+		}
+	}
+
+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
+		if (crtc_state->plane_mask != crtc->state->plane_mask ||
+		    crtc_state->zpos_changed) {
+			ret = drm_atomic_helper_crtc_normalize_zpos(crtc,
+								    crtc_state);
+			if (ret)
+				return ret;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL(drm_atomic_helper_normalize_zpos);
diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
index a78c138..37d9068 100644
--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h
@@ -42,3 +42,6 @@  int drm_atomic_get_property(struct drm_mode_object *obj,
 int drm_mode_atomic_ioctl(struct drm_device *dev,
 			  void *data, struct drm_file *file_priv);
 
+/* drm_blend.c */
+int drm_atomic_helper_normalize_zpos(struct drm_device *dev,
+				     struct drm_atomic_state *state);
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index d1559cd..a34bc29 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -305,6 +305,7 @@  struct drm_plane_helper_funcs;
  * @mode_changed: crtc_state->mode or crtc_state->enable has been changed
  * @active_changed: crtc_state->active has been toggled.
  * @connectors_changed: connectors to this crtc have been updated
+ * @zpos_changed: zpos values of planes on this crtc have been updated
  * @color_mgmt_changed: color management properties have changed (degamma or
  *	gamma LUT or CSC matrix)
  * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
@@ -340,6 +341,7 @@  struct drm_crtc_state {
 	bool mode_changed : 1;
 	bool active_changed : 1;
 	bool connectors_changed : 1;
+	bool zpos_changed : 1;
 	bool color_mgmt_changed : 1;
 
 	/* attached planes bitmask:
@@ -1263,6 +1265,9 @@  struct drm_connector {
  *	plane (in 16.16)
  * @src_w: width of visible portion of plane (in 16.16)
  * @src_h: height of visible portion of plane (in 16.16)
+ * @zpos: priority of the given plane on crtc (optional)
+ * @normalized_zpos: normalized value of zpos: unique, range from 0 to N
+ *	 for given crtc
  * @state: backpointer to global drm_atomic_state
  */
 struct drm_plane_state {
@@ -1283,6 +1288,10 @@  struct drm_plane_state {
 	/* Plane rotation */
 	unsigned int rotation;
 
+	/* Plane zpos */
+	unsigned int zpos;
+	unsigned int normalized_zpos;
+
 	struct drm_atomic_state *state;
 };
 
@@ -2554,6 +2563,22 @@  extern struct drm_property *drm_mode_create_rotation_property(struct drm_device
 extern unsigned int drm_rotation_simplify(unsigned int rotation,
 					  unsigned int supported_rotations);
 
+extern int drm_plane_atomic_set_zpos_property(struct drm_plane *plane,
+					      struct drm_plane_state *state,
+					      struct drm_property *property,
+					      uint64_t val);
+
+extern int drm_plane_atomic_get_zpos_property(struct drm_plane *plane,
+					      const struct drm_plane_state *state,
+					      struct drm_property *property,
+					      uint64_t *val);
+
+extern int drm_plane_create_zpos_property(struct drm_plane *plane,
+					  unsigned int min, unsigned int max);
+extern int drm_plane_create_zpos_immutable_property(struct drm_plane *plane,
+						    unsigned int min,
+						    unsigned int max);
+
 /* Helpers */
 
 static inline struct drm_plane *drm_plane_find(struct drm_device *dev,