[v3,05/10] drm: Add helpers to kick off self refresh mode in drivers

Commit Message

Sean Paul May 2, 2019, 7:49 p.m. UTC

From: Sean Paul <[e-mail]>

This patch adds a new drm helper library to help drivers implement
self refresh. Drivers choosing to use it will register crtcs and
will receive callbacks when it's time to enter or exit self refresh
mode.

In its current form, it has a timer which will trigger after a
driver-specified amount of inactivity. When the timer triggers, the
helpers will submit a new atomic commit to shut the refreshing pipe
off. On the next atomic commit, the drm core will revert the self
refresh state and bring everything back up to be actively driven.

From the driver's perspective, this works like a regular disable/enable
cycle. The driver need only check the 'self_refresh_active' state in
crtc_state. It should initiate self refresh mode on the panel and enter
an off or low-power state.

Changes in v2:
- s/psr/self_refresh/ (Daniel)
- integrated the psr exit into the commit that wakes it up (Jose/Daniel)
- made the psr state per-crtc (Jose/Daniel)
Changes in v3:
- Remove the self_refresh_(active|changed) from connector state (Daniel)
- Simplify loop in drm_self_refresh_helper_alter_state (Daniel)
- Improve self_refresh_aware comment (Daniel)
- s/self_refresh_state/self_refresh_data/ (Daniel)

Link to v1: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
Link to v2: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

Cc: Daniel Vetter <[e-mail]>
Cc: Jose Souza <[e-mail]>
Cc: Zain Wang <[e-mail]>
Cc: Tomasz Figa <[e-mail]>
Cc: Ville Syrjälä <[e-mail]>
Signed-off-by: Sean Paul <[e-mail]>
---
 Documentation/gpu/drm-kms-helpers.rst     |   9 +
 drivers/gpu/drm/Makefile                  |   2 +-
 drivers/gpu/drm/drm_atomic.c              |   2 +
 drivers/gpu/drm/drm_atomic_helper.c       |  35 +++-
 drivers/gpu/drm/drm_atomic_state_helper.c |   4 +
 drivers/gpu/drm/drm_atomic_uapi.c         |   7 +-
 drivers/gpu/drm/drm_self_refresh_helper.c | 205 ++++++++++++++++++++++
 include/drm/drm_atomic.h                  |  15 ++
 include/drm/drm_connector.h               |  14 ++
 include/drm/drm_crtc.h                    |  19 ++
 include/drm/drm_self_refresh_helper.h     |  22 +++
 11 files changed, 329 insertions(+), 5 deletions(-)
 create mode 100644 drivers/gpu/drm/drm_self_refresh_helper.c
 create mode 100644 include/drm/drm_self_refresh_helper.h

Comments

Daniel Vetter May 3, 2019, 7:36 a.m. UTC | #1

On Thu, May 02, 2019 at 03:49:47PM -0400, Sean Paul wrote:
> From: Sean Paul <[e-mail]>
> 
> This patch adds a new drm helper library to help drivers implement
> self refresh. Drivers choosing to use it will register crtcs and
> will receive callbacks when it's time to enter or exit self refresh
> mode.
> 
> In its current form, it has a timer which will trigger after a
> driver-specified amount of inactivity. When the timer triggers, the
> helpers will submit a new atomic commit to shut the refreshing pipe
> off. On the next atomic commit, the drm core will revert the self
> refresh state and bring everything back up to be actively driven.
> 
> From the driver's perspective, this works like a regular disable/enable
> cycle. The driver need only check the 'self_refresh_active' state in
> crtc_state. It should initiate self refresh mode on the panel and enter
> an off or low-power state.
> 
> Changes in v2:
> - s/psr/self_refresh/ (Daniel)
> - integrated the psr exit into the commit that wakes it up (Jose/Daniel)
> - made the psr state per-crtc (Jose/Daniel)
> Changes in v3:
> - Remove the self_refresh_(active|changed) from connector state (Daniel)
> - Simplify loop in drm_self_refresh_helper_alter_state (Daniel)
> - Improve self_refresh_aware comment (Daniel)
> - s/self_refresh_state/self_refresh_data/ (Daniel)
> 
> Link to v1: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
> Link to v2: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
> 
> Cc: Daniel Vetter <[e-mail]>
> Cc: Jose Souza <[e-mail]>
> Cc: Zain Wang <[e-mail]>
> Cc: Tomasz Figa <[e-mail]>
> Cc: Ville Syrjälä <[e-mail]>
> Signed-off-by: Sean Paul <[e-mail]>

lgtm now, thanks a lot for sticking with this! Surprising lots of corner
cases I had to learn about and figure out what to best do with them.

> ---
>  Documentation/gpu/drm-kms-helpers.rst     |   9 +
>  drivers/gpu/drm/Makefile                  |   2 +-
>  drivers/gpu/drm/drm_atomic.c              |   2 +
>  drivers/gpu/drm/drm_atomic_helper.c       |  35 +++-
>  drivers/gpu/drm/drm_atomic_state_helper.c |   4 +
>  drivers/gpu/drm/drm_atomic_uapi.c         |   7 +-
>  drivers/gpu/drm/drm_self_refresh_helper.c | 205 ++++++++++++++++++++++
>  include/drm/drm_atomic.h                  |  15 ++
>  include/drm/drm_connector.h               |  14 ++
>  include/drm/drm_crtc.h                    |  19 ++
>  include/drm/drm_self_refresh_helper.h     |  22 +++
>  11 files changed, 329 insertions(+), 5 deletions(-)
>  create mode 100644 drivers/gpu/drm/drm_self_refresh_helper.c
>  create mode 100644 include/drm/drm_self_refresh_helper.h
> 
> diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
> index 14102ae035dc..d8a13c6b4db3 100644
> --- a/Documentation/gpu/drm-kms-helpers.rst
> +++ b/Documentation/gpu/drm-kms-helpers.rst
> @@ -113,6 +113,15 @@ format Helper Functions Reference
>  .. kernel-doc:: drivers/gpu/drm/drm_format_helper.c
>     :export:
>  
> +Panel Self Refresh Helper Reference
> +===================================
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_self_refresh_helper.c
> +   :doc: overview
> +
> +.. kernel-doc:: drivers/gpu/drm/drm_self_refresh_helper.c
> +   :export:

I think this isn't the best place to insert the self refresh helpers. I'd
put them right below panel helpers, together with the other sink related
stuff. I think fits much better there than between the format and gem
helpers ...

> +
>  Framebuffer CMA Helper Functions Reference
>  ==========================================
>  
> diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
> index 3d0c75cd687c..c4852604fc1d 100644
> --- a/drivers/gpu/drm/Makefile
> +++ b/drivers/gpu/drm/Makefile
> @@ -39,7 +39,7 @@ drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper
>  		drm_simple_kms_helper.o drm_modeset_helper.o \
>  		drm_scdc_helper.o drm_gem_framebuffer_helper.o \
>  		drm_atomic_state_helper.o drm_damage_helper.o \
> -		drm_format_helper.o
> +		drm_format_helper.o drm_self_refresh_helper.o
>  
>  drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
>  drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 5eb40130fafb..4449956241f2 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -379,6 +379,7 @@ static void drm_atomic_crtc_print_state(struct drm_printer *p,
>  	drm_printf(p, "crtc[%u]: %s\n", crtc->base.id, crtc->name);
>  	drm_printf(p, "\tenable=%d\n", state->enable);
>  	drm_printf(p, "\tactive=%d\n", state->active);
> +	drm_printf(p, "\tself_refresh_active=%d\n", state->self_refresh_active);
>  	drm_printf(p, "\tplanes_changed=%d\n", state->planes_changed);
>  	drm_printf(p, "\tmode_changed=%d\n", state->mode_changed);
>  	drm_printf(p, "\tactive_changed=%d\n", state->active_changed);
> @@ -881,6 +882,7 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  
>  	drm_printf(p, "connector[%u]: %s\n", connector->base.id, connector->name);
>  	drm_printf(p, "\tcrtc=%s\n", state->crtc ? state->crtc->name : "(null)");
> +	drm_printf(p, "\tself_refresh_aware=%d\n", state->self_refresh_aware);
>  
>  	if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
>  		if (state->writeback_job && state->writeback_job->fb)
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index fa5a367507c1..3c26f04cd6b8 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -30,6 +30,7 @@
>  #include <drm/drm_atomic_uapi.h>
>  #include <drm/drm_plane_helper.h>
>  #include <drm/drm_atomic_helper.h>
> +#include <drm/drm_self_refresh_helper.h>
>  #include <drm/drm_writeback.h>
>  #include <drm/drm_damage_helper.h>
>  #include <linux/dma-fence.h>
> @@ -950,10 +951,33 @@ int drm_atomic_helper_check(struct drm_device *dev,
>  	if (state->legacy_cursor_update)
>  		state->async_update = !drm_atomic_helper_async_check(dev, state);
>  
> +	drm_self_refresh_helper_alter_state(state);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(drm_atomic_helper_check);
>  
> +static bool
> +crtc_needs_disable(struct drm_crtc_state *old_state,
> +		   struct drm_crtc_state *new_state)
> +{
> +	/*
> +	 * No new_state means the crtc is off, so the only criteria is whether
> +	 * it's currently active or in self refresh mode.
> +	 */
> +	if (!new_state)
> +		return drm_atomic_crtc_effectively_active(old_state);
> +
> +	/*
> +	 * We need to run through the crtc_funcs->disable() function if the crtc
> +	 * is currently on, if it's transitioning to self refresh mode, or if
> +	 * it's in self refresh mode and needs to be fully disabled.
> +	 */
> +	return old_state->active ||
> +	       (old_state->self_refresh_active && !new_state->enable) ||
> +	       new_state->self_refresh_active;
> +}
> +
>  static void
>  disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>  {
> @@ -974,7 +998,14 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>  
>  		old_crtc_state = drm_atomic_get_old_crtc_state(old_state, old_conn_state->crtc);
>  
> -		if (!old_crtc_state->active ||
> +		if (new_conn_state->crtc)
> +			new_crtc_state = drm_atomic_get_new_crtc_state(
> +						old_state,
> +						new_conn_state->crtc);
> +		else
> +			new_crtc_state = NULL;
> +
> +		if (!crtc_needs_disable(old_crtc_state, new_crtc_state) ||
>  		    !drm_atomic_crtc_needs_modeset(old_conn_state->crtc->state))
>  			continue;
>  
> @@ -1020,7 +1051,7 @@ disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
>  		if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
>  			continue;
>  
> -		if (!old_crtc_state->active)
> +		if (!crtc_needs_disable(old_crtc_state, new_crtc_state))
>  			continue;
>  
>  		funcs = crtc->helper_private;
> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> index ac929f68ff31..ca18008043e5 100644
> --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> @@ -128,6 +128,10 @@ void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc,
>  	state->commit = NULL;
>  	state->event = NULL;
>  	state->pageflip_flags = 0;
> +
> +	/* Self refresh should be canceled when a new update is available */
> +	state->active = drm_atomic_crtc_effectively_active(state);
> +	state->self_refresh_active = false;
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_crtc_duplicate_state);
>  
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
> index ea797d4c82ee..a75c633ff0c0 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -490,7 +490,7 @@ drm_atomic_crtc_get_property(struct drm_crtc *crtc,
>  	struct drm_mode_config *config = &dev->mode_config;
>  
>  	if (property == config->prop_active)
> -		*val = state->active;
> +		*val = drm_atomic_crtc_effectively_active(state);
>  	else if (property == config->prop_mode_id)
>  		*val = (state->mode_blob) ? state->mode_blob->base.id : 0;
>  	else if (property == config->prop_vrr_enabled)
> @@ -772,7 +772,10 @@ drm_atomic_connector_get_property(struct drm_connector *connector,
>  	if (property == config->prop_crtc_id) {
>  		*val = (state->crtc) ? state->crtc->base.id : 0;
>  	} else if (property == config->dpms_property) {
> -		*val = connector->dpms;
> +		if (state->crtc && state->crtc->state->self_refresh_active)
> +			*val = DRM_MODE_DPMS_ON;
> +		else
> +			*val = connector->dpms;
>  	} else if (property == config->tv_select_subconnector_property) {
>  		*val = state->tv.subconnector;
>  	} else if (property == config->tv_left_margin_property) {
> diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c
> new file mode 100644
> index 000000000000..f46e7639d277
> --- /dev/null
> +++ b/drivers/gpu/drm/drm_self_refresh_helper.c
> @@ -0,0 +1,205 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright (C) 2019 Google, Inc.
> + *
> + * Authors:
> + * Sean Paul <[e-mail]>
> + */
> +#include <drm/drm_atomic.h>
> +#include <drm/drm_atomic_helper.h>
> +#include <drm/drm_connector.h>
> +#include <drm/drm_crtc.h>
> +#include <drm/drm_device.h>
> +#include <drm/drm_mode_config.h>
> +#include <drm/drm_modeset_lock.h>
> +#include <drm/drm_print.h>
> +#include <drm/drm_self_refresh_helper.h>
> +#include <linux/bitops.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +
> +/**
> + * DOC: overview
> + *
> + * This helper library provides an easy way for drivers to leverage the atomic
> + * framework to implement panel self refresh (SR) support. Drivers are
> + * responsible for registering and unregistering the SR helpers on load/unload.

I think better if you mention that you both need to set up the CRTC (using
the init/cleanup functions), and also the connector (by setting
&drm_connector.self_refresh_aware).
> + *
> + * Once a crtc has enabled SR, the helpers will monitor activity and
> + * call back into the driver to enable/disable SR as appropriate. The best way
> + * to think about this is that it's a DPMS on/off request with a flag set in
> + * state that tells you to disable/enable SR on the panel instead of power-
> + * cycling it.
> + *
> + * Drivers may choose to fully disable their crtc/encoder/bridge hardware, or
> + * they can use the "self_refresh_active" flags in crtc state if they want to
> + * enter low power mode without full disable (in case full disable/enable is too
> + * slow).
> + *
> + * SR will be deactivated if there are any atomic updates affecting the
> + * pipe that is in SR mode. If a crtc is driving multiple connectors, all
> + * connectors must be SR aware and all will enter SR mode.

I think the above text would be more useful if you spice it up with links
to the relevant functions (init/cleanup and alter_state) plus what to look
at, i.e. &drm_crtc_state.self_refresh_active.

> + */
> +
> +struct drm_self_refresh_data {
> +	struct drm_crtc *crtc;
> +	struct delayed_work entry_work;
> +	struct drm_atomic_state *save_state;
> +	unsigned int entry_delay_ms;
> +};
> +
> +static void drm_self_refresh_helper_entry_work(struct work_struct *work)
> +{
> +	struct drm_self_refresh_data *sr_data = container_of(
> +				to_delayed_work(work),
> +				struct drm_self_refresh_data, entry_work);
> +	struct drm_crtc *crtc = sr_data->crtc;
> +	struct drm_device *dev = crtc->dev;
> +	struct drm_modeset_acquire_ctx ctx;
> +	struct drm_atomic_state *state;
> +	struct drm_connector *conn;
> +	struct drm_connector_state *conn_state;
> +	struct drm_crtc_state *crtc_state;
> +	int i, ret;
> +
> +	drm_modeset_acquire_init(&ctx, 0);
> +
> +	state = drm_atomic_state_alloc(dev);
> +	if (!state) {
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
> +retry:
> +	state->acquire_ctx = &ctx;
> +
> +	crtc_state = drm_atomic_get_crtc_state(state, crtc);
> +	if (IS_ERR(crtc_state)) {
> +		ret = PTR_ERR(crtc_state);
> +		goto out;
> +	}
> +
> +	if (!crtc_state->enable)
> +		goto out;
> +
> +	ret = drm_atomic_add_affected_connectors(state, crtc);
> +	if (ret)
> +		goto out;
> +
> +	for_each_new_connector_in_state(state, conn, conn_state, i) {
> +		if (!conn_state->self_refresh_aware)
> +			goto out;
> +	}
> +
> +	crtc_state->active = false;
> +	crtc_state->self_refresh_active = true;
> +
> +	ret = drm_atomic_commit(state);
> +	if (ret)
> +		goto out;
> +
> +out:
> +	if (ret == -EDEADLK) {
> +		drm_atomic_state_clear(state);
> +		ret = drm_modeset_backoff(&ctx);
> +		if (!ret)
> +			goto retry;
> +	}
> +
> +	drm_atomic_state_put(state);
> +	drm_modeset_drop_locks(&ctx);
> +	drm_modeset_acquire_fini(&ctx);
> +}
> +
> +/**
> + * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit
> + * @state: the state currently being checked
> + *
> + * Called at the end of atomic check. This function checks the state for flags
> + * incompatible with self refresh exit and changes them. This is a bit
> + * disingenuous since userspace is expecting one thing and we're giving it
> + * another. However in order to keep self refresh entirely hidden from
> + * userspace, this is required.
> + *
> + * At the end, we queue up the self refresh entry work so we can enter PSR after
> + * the desired delay.
> + */
> +void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *crtc_state;
> +	int i;
> +
> +	if (state->async_update || !state->allow_modeset) {
> +		for_each_old_crtc_in_state(state, crtc, crtc_state, i) {
> +			if (crtc_state->self_refresh_active) {
> +				state->async_update = false;
> +				state->allow_modeset = true;
> +				break;
> +			}
> +		}
> +	}
> +
> +	for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> +		struct drm_self_refresh_data *sr_data;
> +
> +		/* Don't trigger the entry timer when we're already in SR */
> +		if (crtc_state->self_refresh_active)
> +			continue;
> +
> +		sr_data = crtc->self_refresh_data;
> +		if (!sr_data)
> +			continue;
> +
> +		mod_delayed_work(system_wq, &sr_data->entry_work,
> +				 msecs_to_jiffies(sr_data->entry_delay_ms));
> +	}
> +}
> +EXPORT_SYMBOL(drm_self_refresh_helper_alter_state);
> +
> +/**
> + * drm_self_refresh_helper_register - Registers self refresh helpers for a crtc
> + * @crtc: the crtc which supports self refresh supported displays
> + * @entry_delay_ms: amount of inactivity to wait before entering self refresh
> + */
> +int drm_self_refresh_helper_register(struct drm_crtc *crtc,
> +				     unsigned int entry_delay_ms)
> +{

Bikeshed that I missed in previous rounds: _register/_unregister has
pretty clear meaning of "(un)publish an interface to userspace".
_init/_cleanup are the common ones.

> +	struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
> +
> +	/* Helper is already registered */
> +	if (WARN_ON(sr_data))
> +		return -EINVAL;
> +
> +	sr_data = kzalloc(sizeof(*sr_data), GFP_KERNEL);
> +	if (!sr_data)
> +		return -ENOMEM;
> +
> +	INIT_DELAYED_WORK(&sr_data->entry_work,
> +			  drm_self_refresh_helper_entry_work);
> +	sr_data->entry_delay_ms = entry_delay_ms;
> +	sr_data->crtc = crtc;
> +
> +	crtc->self_refresh_data = sr_data;
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_self_refresh_helper_register);
> +
> +/**
> + * drm_self_refresh_helper_unregister - Unregisters self refresh helpers
> + * @crtc: the crtc to unregister
> + */
> +void drm_self_refresh_helper_unregister(struct drm_crtc *crtc)
> +{
> +	struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
> +
> +	/* Helper is already unregistered */
> +	if (sr_data)
> +		return;
> +
> +	crtc->self_refresh_data = NULL;
> +
> +	cancel_delayed_work_sync(&sr_data->entry_work);
> +	kfree(sr_data);
> +}
> +EXPORT_SYMBOL(drm_self_refresh_helper_unregister);
> diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
> index 824a5ed4e216..1e9cab1da97a 100644
> --- a/include/drm/drm_atomic.h
> +++ b/include/drm/drm_atomic.h
> @@ -944,4 +944,19 @@ drm_atomic_crtc_needs_modeset(const struct drm_crtc_state *state)
>  	       state->connectors_changed;
>  }
>  
> +/**
> + * drm_atomic_crtc_effectively_active - compute whether crtc is actually active
> + * @state: &drm_crtc_state for the CRTC
> + *
> + * When in self refresh mode, the crtc_state->active value will be false, since
> + * the crtc is off. However in some cases we're interested in whether the crtc
> + * is active, or effectively active (ie: it's connected to an active display).
> + * In these cases, use this function instead of just checking active.
> + */
> +static inline bool
> +drm_atomic_crtc_effectively_active(const struct drm_crtc_state *state)
> +{
> +	return state->active || state->self_refresh_active;
> +}
> +
>  #endif /* DRM_ATOMIC_H_ */
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 02a131202add..9b40eb6f0ef4 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -539,6 +539,20 @@ struct drm_connector_state {
>  	/** @tv: TV connector state */
>  	struct drm_tv_connector_state tv;
>  
> +	/**
> +	 * @self_refresh_aware:
> +	 *
> +	 * This tracks whether a connector is aware of the self refresh state.
> +	 * It should be set to true for those connector implementations which
> +	 * understand the self refresh state. This is needed since the crtc
> +	 * registers the self refresh helpers and it doesn't know if the
> +	 * connectors downstream have implemented self refresh entry/exit.
> +	 *
> +	 * Drivers should set this to true in atomic_check if they know how to
> +	 * handle self_refresh requests.
> +	 */
> +	bool self_refresh_aware;
> +
>  	/**
>  	 * @picture_aspect_ratio: Connector property to control the
>  	 * HDMI infoframe aspect ratio setting.
> diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
> index 58ad983d7cd6..67e3075a8784 100644
> --- a/include/drm/drm_crtc.h
> +++ b/include/drm/drm_crtc.h
> @@ -53,6 +53,7 @@ struct drm_mode_set;
>  struct drm_file;
>  struct drm_clip_rect;
>  struct drm_printer;
> +struct drm_self_refresh_data;
>  struct device_node;
>  struct dma_fence;
>  struct edid;
> @@ -299,6 +300,17 @@ struct drm_crtc_state {
>  	 */
>  	bool vrr_enabled;
>  
> +	/**
> +	 * @self_refresh_active:
> +	 *
> +	 * Used by the self refresh helpers to denote when a self refresh
> +	 * transition is occuring. This will be set on enable/disable callbacks
> +	 * when self refresh is being enabled or disabled. In some cases, it may
> +	 * not be desirable to fully shut off the crtc during self refresh.
> +	 * CRTC's can inspect this flag and determine the best course of action.
> +	 */
> +	bool self_refresh_active;
> +
>  	/**
>  	 * @event:
>  	 *
> @@ -1087,6 +1099,13 @@ struct drm_crtc {
>  	 * The name of the CRTC's fence timeline.
>  	 */
>  	char timeline_name[32];
> +
> +	/**
> +	 * @self_refresh_data: Holds the state for the self refresh helpers
> +	 *
> +	 * Initialized via drm_self_refresh_helper_register().
> +	 */
> +	struct drm_self_refresh_data *self_refresh_data;
>  };
>  
>  /**
> diff --git a/include/drm/drm_self_refresh_helper.h b/include/drm/drm_self_refresh_helper.h
> new file mode 100644
> index 000000000000..efb2e6e3249f
> --- /dev/null
> +++ b/include/drm/drm_self_refresh_helper.h
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: MIT */
> +/*
> + * Copyright (C) 2019 Google, Inc.
> + *
> + * Authors:
> + * Sean Paul <[e-mail]>
> + */
> +#ifndef DRM_SELF_REFRESH_HELPER_H_
> +#define DRM_SELF_REFRESH_HELPER_H_
> +
> +struct drm_atomic_state;
> +struct drm_connector;
> +struct drm_device;
> +struct drm_modeset_acquire_ctx;
> +
> +void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state);
> +
> +int drm_self_refresh_helper_register(struct drm_crtc *crtc,
> +				     unsigned int entry_delay_ms);
> +
> +void drm_self_refresh_helper_unregister(struct drm_crtc *crtc);
> +#endif

With the remaining nits addressed: Reviewed-by: Daniel Vetter <[e-mail]>

Patch

diff --git a/Documentation/gpu/drm-kms-helpers.rst b/Documentation/gpu/drm-kms-helpers.rst
index 14102ae035dc..d8a13c6b4db3 100644
--- a/Documentation/gpu/drm-kms-helpers.rst
+++ b/Documentation/gpu/drm-kms-helpers.rst
@@ -113,6 +113,15 @@  format Helper Functions Reference
 .. kernel-doc:: drivers/gpu/drm/drm_format_helper.c
    :export:
 
+Panel Self Refresh Helper Reference
+===================================
+
+.. kernel-doc:: drivers/gpu/drm/drm_self_refresh_helper.c
+   :doc: overview
+
+.. kernel-doc:: drivers/gpu/drm/drm_self_refresh_helper.c
+   :export:
+
 Framebuffer CMA Helper Functions Reference
 ==========================================
 
diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index 3d0c75cd687c..c4852604fc1d 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -39,7 +39,7 @@  drm_kms_helper-y := drm_crtc_helper.o drm_dp_helper.o drm_dsc.o drm_probe_helper
 		drm_simple_kms_helper.o drm_modeset_helper.o \
 		drm_scdc_helper.o drm_gem_framebuffer_helper.o \
 		drm_atomic_state_helper.o drm_damage_helper.o \
-		drm_format_helper.o
+		drm_format_helper.o drm_self_refresh_helper.o
 
 drm_kms_helper-$(CONFIG_DRM_PANEL_BRIDGE) += bridge/panel.o
 drm_kms_helper-$(CONFIG_DRM_FBDEV_EMULATION) += drm_fb_helper.o
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 5eb40130fafb..4449956241f2 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -379,6 +379,7 @@  static void drm_atomic_crtc_print_state(struct drm_printer *p,
 	drm_printf(p, "crtc[%u]: %s\n", crtc->base.id, crtc->name);
 	drm_printf(p, "\tenable=%d\n", state->enable);
 	drm_printf(p, "\tactive=%d\n", state->active);
+	drm_printf(p, "\tself_refresh_active=%d\n", state->self_refresh_active);
 	drm_printf(p, "\tplanes_changed=%d\n", state->planes_changed);
 	drm_printf(p, "\tmode_changed=%d\n", state->mode_changed);
 	drm_printf(p, "\tactive_changed=%d\n", state->active_changed);
@@ -881,6 +882,7 @@  static void drm_atomic_connector_print_state(struct drm_printer *p,
 
 	drm_printf(p, "connector[%u]: %s\n", connector->base.id, connector->name);
 	drm_printf(p, "\tcrtc=%s\n", state->crtc ? state->crtc->name : "(null)");
+	drm_printf(p, "\tself_refresh_aware=%d\n", state->self_refresh_aware);
 
 	if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
 		if (state->writeback_job && state->writeback_job->fb)
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index fa5a367507c1..3c26f04cd6b8 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -30,6 +30,7 @@ 
 #include <drm/drm_atomic_uapi.h>
 #include <drm/drm_plane_helper.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_self_refresh_helper.h>
 #include <drm/drm_writeback.h>
 #include <drm/drm_damage_helper.h>
 #include <linux/dma-fence.h>
@@ -950,10 +951,33 @@  int drm_atomic_helper_check(struct drm_device *dev,
 	if (state->legacy_cursor_update)
 		state->async_update = !drm_atomic_helper_async_check(dev, state);
 
+	drm_self_refresh_helper_alter_state(state);
+
 	return ret;
 }
 EXPORT_SYMBOL(drm_atomic_helper_check);
 
+static bool
+crtc_needs_disable(struct drm_crtc_state *old_state,
+		   struct drm_crtc_state *new_state)
+{
+	/*
+	 * No new_state means the crtc is off, so the only criteria is whether
+	 * it's currently active or in self refresh mode.
+	 */
+	if (!new_state)
+		return drm_atomic_crtc_effectively_active(old_state);
+
+	/*
+	 * We need to run through the crtc_funcs->disable() function if the crtc
+	 * is currently on, if it's transitioning to self refresh mode, or if
+	 * it's in self refresh mode and needs to be fully disabled.
+	 */
+	return old_state->active ||
+	       (old_state->self_refresh_active && !new_state->enable) ||
+	       new_state->self_refresh_active;
+}
+
 static void
 disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 {
@@ -974,7 +998,14 @@  disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 
 		old_crtc_state = drm_atomic_get_old_crtc_state(old_state, old_conn_state->crtc);
 
-		if (!old_crtc_state->active ||
+		if (new_conn_state->crtc)
+			new_crtc_state = drm_atomic_get_new_crtc_state(
+						old_state,
+						new_conn_state->crtc);
+		else
+			new_crtc_state = NULL;
+
+		if (!crtc_needs_disable(old_crtc_state, new_crtc_state) ||
 		    !drm_atomic_crtc_needs_modeset(old_conn_state->crtc->state))
 			continue;
 
@@ -1020,7 +1051,7 @@  disable_outputs(struct drm_device *dev, struct drm_atomic_state *old_state)
 		if (!drm_atomic_crtc_needs_modeset(new_crtc_state))
 			continue;
 
-		if (!old_crtc_state->active)
+		if (!crtc_needs_disable(old_crtc_state, new_crtc_state))
 			continue;
 
 		funcs = crtc->helper_private;
diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
index ac929f68ff31..ca18008043e5 100644
--- a/drivers/gpu/drm/drm_atomic_state_helper.c
+++ b/drivers/gpu/drm/drm_atomic_state_helper.c
@@ -128,6 +128,10 @@  void __drm_atomic_helper_crtc_duplicate_state(struct drm_crtc *crtc,
 	state->commit = NULL;
 	state->event = NULL;
 	state->pageflip_flags = 0;
+
+	/* Self refresh should be canceled when a new update is available */
+	state->active = drm_atomic_crtc_effectively_active(state);
+	state->self_refresh_active = false;
 }
 EXPORT_SYMBOL(__drm_atomic_helper_crtc_duplicate_state);
 
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index ea797d4c82ee..a75c633ff0c0 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -490,7 +490,7 @@  drm_atomic_crtc_get_property(struct drm_crtc *crtc,
 	struct drm_mode_config *config = &dev->mode_config;
 
 	if (property == config->prop_active)
-		*val = state->active;
+		*val = drm_atomic_crtc_effectively_active(state);
 	else if (property == config->prop_mode_id)
 		*val = (state->mode_blob) ? state->mode_blob->base.id : 0;
 	else if (property == config->prop_vrr_enabled)
@@ -772,7 +772,10 @@  drm_atomic_connector_get_property(struct drm_connector *connector,
 	if (property == config->prop_crtc_id) {
 		*val = (state->crtc) ? state->crtc->base.id : 0;
 	} else if (property == config->dpms_property) {
-		*val = connector->dpms;
+		if (state->crtc && state->crtc->state->self_refresh_active)
+			*val = DRM_MODE_DPMS_ON;
+		else
+			*val = connector->dpms;
 	} else if (property == config->tv_select_subconnector_property) {
 		*val = state->tv.subconnector;
 	} else if (property == config->tv_left_margin_property) {
diff --git a/drivers/gpu/drm/drm_self_refresh_helper.c b/drivers/gpu/drm/drm_self_refresh_helper.c
new file mode 100644
index 000000000000..f46e7639d277
--- /dev/null
+++ b/drivers/gpu/drm/drm_self_refresh_helper.c
@@ -0,0 +1,205 @@ 
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright (C) 2019 Google, Inc.
+ *
+ * Authors:
+ * Sean Paul <[e-mail]>
+ */
+#include <drm/drm_atomic.h>
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_connector.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_device.h>
+#include <drm/drm_mode_config.h>
+#include <drm/drm_modeset_lock.h>
+#include <drm/drm_print.h>
+#include <drm/drm_self_refresh_helper.h>
+#include <linux/bitops.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+
+/**
+ * DOC: overview
+ *
+ * This helper library provides an easy way for drivers to leverage the atomic
+ * framework to implement panel self refresh (SR) support. Drivers are
+ * responsible for registering and unregistering the SR helpers on load/unload.
+ *
+ * Once a crtc has enabled SR, the helpers will monitor activity and
+ * call back into the driver to enable/disable SR as appropriate. The best way
+ * to think about this is that it's a DPMS on/off request with a flag set in
+ * state that tells you to disable/enable SR on the panel instead of power-
+ * cycling it.
+ *
+ * Drivers may choose to fully disable their crtc/encoder/bridge hardware, or
+ * they can use the "self_refresh_active" flags in crtc state if they want to
+ * enter low power mode without full disable (in case full disable/enable is too
+ * slow).
+ *
+ * SR will be deactivated if there are any atomic updates affecting the
+ * pipe that is in SR mode. If a crtc is driving multiple connectors, all
+ * connectors must be SR aware and all will enter SR mode.
+ */
+
+struct drm_self_refresh_data {
+	struct drm_crtc *crtc;
+	struct delayed_work entry_work;
+	struct drm_atomic_state *save_state;
+	unsigned int entry_delay_ms;
+};
+
+static void drm_self_refresh_helper_entry_work(struct work_struct *work)
+{
+	struct drm_self_refresh_data *sr_data = container_of(
+				to_delayed_work(work),
+				struct drm_self_refresh_data, entry_work);
+	struct drm_crtc *crtc = sr_data->crtc;
+	struct drm_device *dev = crtc->dev;
+	struct drm_modeset_acquire_ctx ctx;
+	struct drm_atomic_state *state;
+	struct drm_connector *conn;
+	struct drm_connector_state *conn_state;
+	struct drm_crtc_state *crtc_state;
+	int i, ret;
+
+	drm_modeset_acquire_init(&ctx, 0);
+
+	state = drm_atomic_state_alloc(dev);
+	if (!state) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+retry:
+	state->acquire_ctx = &ctx;
+
+	crtc_state = drm_atomic_get_crtc_state(state, crtc);
+	if (IS_ERR(crtc_state)) {
+		ret = PTR_ERR(crtc_state);
+		goto out;
+	}
+
+	if (!crtc_state->enable)
+		goto out;
+
+	ret = drm_atomic_add_affected_connectors(state, crtc);
+	if (ret)
+		goto out;
+
+	for_each_new_connector_in_state(state, conn, conn_state, i) {
+		if (!conn_state->self_refresh_aware)
+			goto out;
+	}
+
+	crtc_state->active = false;
+	crtc_state->self_refresh_active = true;
+
+	ret = drm_atomic_commit(state);
+	if (ret)
+		goto out;
+
+out:
+	if (ret == -EDEADLK) {
+		drm_atomic_state_clear(state);
+		ret = drm_modeset_backoff(&ctx);
+		if (!ret)
+			goto retry;
+	}
+
+	drm_atomic_state_put(state);
+	drm_modeset_drop_locks(&ctx);
+	drm_modeset_acquire_fini(&ctx);
+}
+
+/**
+ * drm_self_refresh_helper_alter_state - Alters the atomic state for SR exit
+ * @state: the state currently being checked
+ *
+ * Called at the end of atomic check. This function checks the state for flags
+ * incompatible with self refresh exit and changes them. This is a bit
+ * disingenuous since userspace is expecting one thing and we're giving it
+ * another. However in order to keep self refresh entirely hidden from
+ * userspace, this is required.
+ *
+ * At the end, we queue up the self refresh entry work so we can enter PSR after
+ * the desired delay.
+ */
+void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state)
+{
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
+	int i;
+
+	if (state->async_update || !state->allow_modeset) {
+		for_each_old_crtc_in_state(state, crtc, crtc_state, i) {
+			if (crtc_state->self_refresh_active) {
+				state->async_update = false;
+				state->allow_modeset = true;
+				break;
+			}
+		}
+	}
+
+	for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
+		struct drm_self_refresh_data *sr_data;
+
+		/* Don't trigger the entry timer when we're already in SR */
+		if (crtc_state->self_refresh_active)
+			continue;
+
+		sr_data = crtc->self_refresh_data;
+		if (!sr_data)
+			continue;
+
+		mod_delayed_work(system_wq, &sr_data->entry_work,
+				 msecs_to_jiffies(sr_data->entry_delay_ms));
+	}
+}
+EXPORT_SYMBOL(drm_self_refresh_helper_alter_state);
+
+/**
+ * drm_self_refresh_helper_register - Registers self refresh helpers for a crtc
+ * @crtc: the crtc which supports self refresh supported displays
+ * @entry_delay_ms: amount of inactivity to wait before entering self refresh
+ */
+int drm_self_refresh_helper_register(struct drm_crtc *crtc,
+				     unsigned int entry_delay_ms)
+{
+	struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
+
+	/* Helper is already registered */
+	if (WARN_ON(sr_data))
+		return -EINVAL;
+
+	sr_data = kzalloc(sizeof(*sr_data), GFP_KERNEL);
+	if (!sr_data)
+		return -ENOMEM;
+
+	INIT_DELAYED_WORK(&sr_data->entry_work,
+			  drm_self_refresh_helper_entry_work);
+	sr_data->entry_delay_ms = entry_delay_ms;
+	sr_data->crtc = crtc;
+
+	crtc->self_refresh_data = sr_data;
+	return 0;
+}
+EXPORT_SYMBOL(drm_self_refresh_helper_register);
+
+/**
+ * drm_self_refresh_helper_unregister - Unregisters self refresh helpers
+ * @crtc: the crtc to unregister
+ */
+void drm_self_refresh_helper_unregister(struct drm_crtc *crtc)
+{
+	struct drm_self_refresh_data *sr_data = crtc->self_refresh_data;
+
+	/* Helper is already unregistered */
+	if (sr_data)
+		return;
+
+	crtc->self_refresh_data = NULL;
+
+	cancel_delayed_work_sync(&sr_data->entry_work);
+	kfree(sr_data);
+}
+EXPORT_SYMBOL(drm_self_refresh_helper_unregister);
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 824a5ed4e216..1e9cab1da97a 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -944,4 +944,19 @@  drm_atomic_crtc_needs_modeset(const struct drm_crtc_state *state)
 	       state->connectors_changed;
 }
 
+/**
+ * drm_atomic_crtc_effectively_active - compute whether crtc is actually active
+ * @state: &drm_crtc_state for the CRTC
+ *
+ * When in self refresh mode, the crtc_state->active value will be false, since
+ * the crtc is off. However in some cases we're interested in whether the crtc
+ * is active, or effectively active (ie: it's connected to an active display).
+ * In these cases, use this function instead of just checking active.
+ */
+static inline bool
+drm_atomic_crtc_effectively_active(const struct drm_crtc_state *state)
+{
+	return state->active || state->self_refresh_active;
+}
+
 #endif /* DRM_ATOMIC_H_ */
diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
index 02a131202add..9b40eb6f0ef4 100644
--- a/include/drm/drm_connector.h
+++ b/include/drm/drm_connector.h
@@ -539,6 +539,20 @@  struct drm_connector_state {
 	/** @tv: TV connector state */
 	struct drm_tv_connector_state tv;
 
+	/**
+	 * @self_refresh_aware:
+	 *
+	 * This tracks whether a connector is aware of the self refresh state.
+	 * It should be set to true for those connector implementations which
+	 * understand the self refresh state. This is needed since the crtc
+	 * registers the self refresh helpers and it doesn't know if the
+	 * connectors downstream have implemented self refresh entry/exit.
+	 *
+	 * Drivers should set this to true in atomic_check if they know how to
+	 * handle self_refresh requests.
+	 */
+	bool self_refresh_aware;
+
 	/**
 	 * @picture_aspect_ratio: Connector property to control the
 	 * HDMI infoframe aspect ratio setting.
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 58ad983d7cd6..67e3075a8784 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -53,6 +53,7 @@  struct drm_mode_set;
 struct drm_file;
 struct drm_clip_rect;
 struct drm_printer;
+struct drm_self_refresh_data;
 struct device_node;
 struct dma_fence;
 struct edid;
@@ -299,6 +300,17 @@  struct drm_crtc_state {
 	 */
 	bool vrr_enabled;
 
+	/**
+	 * @self_refresh_active:
+	 *
+	 * Used by the self refresh helpers to denote when a self refresh
+	 * transition is occuring. This will be set on enable/disable callbacks
+	 * when self refresh is being enabled or disabled. In some cases, it may
+	 * not be desirable to fully shut off the crtc during self refresh.
+	 * CRTC's can inspect this flag and determine the best course of action.
+	 */
+	bool self_refresh_active;
+
 	/**
 	 * @event:
 	 *
@@ -1087,6 +1099,13 @@  struct drm_crtc {
 	 * The name of the CRTC's fence timeline.
 	 */
 	char timeline_name[32];
+
+	/**
+	 * @self_refresh_data: Holds the state for the self refresh helpers
+	 *
+	 * Initialized via drm_self_refresh_helper_register().
+	 */
+	struct drm_self_refresh_data *self_refresh_data;
 };
 
 /**
diff --git a/include/drm/drm_self_refresh_helper.h b/include/drm/drm_self_refresh_helper.h
new file mode 100644
index 000000000000..efb2e6e3249f
--- /dev/null
+++ b/include/drm/drm_self_refresh_helper.h
@@ -0,0 +1,22 @@ 
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright (C) 2019 Google, Inc.
+ *
+ * Authors:
+ * Sean Paul <[e-mail]>
+ */
+#ifndef DRM_SELF_REFRESH_HELPER_H_
+#define DRM_SELF_REFRESH_HELPER_H_
+
+struct drm_atomic_state;
+struct drm_connector;
+struct drm_device;
+struct drm_modeset_acquire_ctx;
+
+void drm_self_refresh_helper_alter_state(struct drm_atomic_state *state);
+
+int drm_self_refresh_helper_register(struct drm_crtc *crtc,
+				     unsigned int entry_delay_ms);
+
+void drm_self_refresh_helper_unregister(struct drm_crtc *crtc);
+#endif