| Message ID | 1479179603-28476-3-git-send-email-manasi.d.navare@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
None of the other functions that set the connector property hold the mode config locks while setting the connector property, I am following the same convention. Also we dont need to grab and release the locks in i915_modeset_work_func that first validates the modes and then sets this link status property. Manasi On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > In the usual working scenarios, this property is "Good". > If something fails during modeset, the DRM driver can > set the link status to "Bad", prune the mode list based on the > link rate/lane count fallback values and send hotplug uevent > so that userspace that is aware of this property can take an > appropriate action by reprobing connectors and re triggering > a modeset to improve user experience and avoid black screens. > In case of userspace that is not aware of this link status > property, the user experience will be unchanged. > > The reason for adding the property is to handle link training failures, > but it is not limited to DP or link training. For example, if we > implement asynchronous setcrtc, we can use this to report any failures > in that. > > Cc: dri-devel@lists.freedesktop.org > Cc: Jani Nikula <jani.nikula@linux.intel.com> > Cc: Daniel Vetter <daniel.vetter@intel.com> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > --- > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > include/drm/drm_connector.h | 2 ++ > 2 files changed, 40 insertions(+) > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index d4e852f..09f4093 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > } > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > +/** > + * drm_mode_connector_set_link_status_property - Set the link status property of > + * a connector to indicate status of link as a result of link training. > + * @connector: drm connector > + * @link_status: new value of link status property (0: Good, 1: Bad) > + * > + * In usual working scenario, this link status property will always be set to > + * "GOOD". > + * If something fails during or after a mode set, the kernel driver can set this > + * link status to "BAD", prune the mode list based on new information and send a > + * hotplug uevent for userspace to have it re-check the valid modes through > + * Get_connector and try again. > + * > + * If userspace is not aware of this property, the user experience is the same > + * as it currently is. If the userspace is aware of the property, it has a chance > + * to improve user experience by handling link training failures, avoiding black > + * screens. The DRM driver can chose to not modify property and keep link status > + * as "GOOD" always to keep the user experience same as it currently is. > + * > + * The reason for adding this property is to handle link training failures, but > + * it is not limited to DP or link training. For example, if we implement > + * asynchronous setcrtc, this property can be used to reportany failures in that. > + * > + * This function must be called from asynchronous work item. > + * Returns zero on success and negative errrno on failure. > + */ > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status) > +{ > + struct drm_device *dev = connector->dev; > + > + connector->link_status = link_status; > + return drm_object_property_set_value(&connector->base, > + dev->mode_config.link_status_property, > + link_status); > +} > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > + > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > struct drm_property *property, > uint64_t value) > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index ad5c8b0..ac76469 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > const struct edid *edid); > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status); > > /** > * drm_for_each_connector - iterate over all connectors > -- > 1.9.1 >
On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > In the usual working scenarios, this property is "Good". > If something fails during modeset, the DRM driver can > set the link status to "Bad", prune the mode list based on the > link rate/lane count fallback values and send hotplug uevent > so that userspace that is aware of this property can take an > appropriate action by reprobing connectors and re triggering > a modeset to improve user experience and avoid black screens. > In case of userspace that is not aware of this link status > property, the user experience will be unchanged. > > The reason for adding the property is to handle link training failures, > but it is not limited to DP or link training. For example, if we > implement asynchronous setcrtc, we can use this to report any failures > in that. > > Cc: dri-devel@lists.freedesktop.org > Cc: Jani Nikula <jani.nikula@linux.intel.com> > Cc: Daniel Vetter <daniel.vetter@intel.com> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > --- > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > include/drm/drm_connector.h | 2 ++ > 2 files changed, 40 insertions(+) > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index d4e852f..09f4093 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > } > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > +/** > + * drm_mode_connector_set_link_status_property - Set the link status property of > + * a connector to indicate status of link as a result of link training. iirc this continuation upsets kernel-doc. Did you build the docs and review them? You need to indent the 2nd line. Also, might just shorten it to "set link status for a connector", details are for the text below. > + * @connector: drm connector > + * @link_status: new value of link status property (0: Good, 1: Bad) > + * > + * In usual working scenario, this link status property will always be set to > + * "GOOD". Unecessary linebbreak. Either make a full paragraph (empty line) or reflow, this here won't survivie kernel-doc formatting. > + * If something fails during or after a mode set, the kernel driver can set this > + * link status to "BAD", prune the mode list based on new information and send a First need to prune the mode list, then set the property. Please reorder in your text. > + * hotplug uevent for userspace to have it re-check the valid modes through > + * Get_connector and try again. s/Get_connector/GET_CONNECTOR IOCTL/ is the more usual style. > + * > + * If userspace is not aware of this property, the user experience is the same > + * as it currently is. If the userspace is aware of the property, it has a chance > + * to improve user experience by handling link training failures, avoiding black > + * screens. The DRM driver can chose to not modify property and keep link status > + * as "GOOD" always to keep the user experience same as it currently is. Imo this paragraph isn't needed. Maybe just mention that old userspace exists: "Note that a lot of existing userspace doesn't handle this property. Drivers can therefore not rely on userspace to fix up everything and should try to handle issues (like just re-training a link) without userspace's intervention. This should only be used when the current mode doesn't work any more, and userspace must select a different display mode." > + * > + * The reason for adding this property is to handle link training failures, but > + * it is not limited to DP or link training. For example, if we implement > + * asynchronous setcrtc, this property can be used to reportany failures in that. s/reportany/report/ > + * > + * This function must be called from asynchronous work item. This isn't true - it doesn't require an asynchronous work item, but the locking rules mean that it. > + * Returns zero on success and negative errrno on failure. Hm, why can this ever fail? Intuitively this should never fail, and hence we shouldn't need an error return value. > + */ > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status) > +{ > + struct drm_device *dev = connector->dev; > + > + connector->link_status = link_status; > + return drm_object_property_set_value(&connector->base, > + dev->mode_config.link_status_property, > + link_status); This misses the hotplug_event call from my proposal. Intentionally? Why? Also: With the current code you require that mode_config.mutex is held by the caller. Every time you add a library/core function which requires certain locks to be held, please check that with something like lockdep_assert_held or similar. Leaking locking rules to callers like this should be the exception, not the rule. But with my proposal this function here would grab all necessary locks, solving that problem, too. -Daniel > +} > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > + > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > struct drm_property *property, > uint64_t value) > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index ad5c8b0..ac76469 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > const struct edid *edid); > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status); > > /** > * drm_for_each_connector - iterate over all connectors > -- > 1.9.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Mon, Nov 14, 2016 at 07:23:33PM -0800, Manasi Navare wrote: > None of the other functions that set the connector property hold the > mode config locks while setting the connector property, I am following > the same convention. > Also we dont need to grab and release the locks in i915_modeset_work_func > that first validates the modes and then sets this link status property. Which other functions don't hold the mode_config.mutex? -Daniel > > Manasi > > On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > > In the usual working scenarios, this property is "Good". > > If something fails during modeset, the DRM driver can > > set the link status to "Bad", prune the mode list based on the > > link rate/lane count fallback values and send hotplug uevent > > so that userspace that is aware of this property can take an > > appropriate action by reprobing connectors and re triggering > > a modeset to improve user experience and avoid black screens. > > In case of userspace that is not aware of this link status > > property, the user experience will be unchanged. > > > > The reason for adding the property is to handle link training failures, > > but it is not limited to DP or link training. For example, if we > > implement asynchronous setcrtc, we can use this to report any failures > > in that. > > > > Cc: dri-devel@lists.freedesktop.org > > Cc: Jani Nikula <jani.nikula@linux.intel.com> > > Cc: Daniel Vetter <daniel.vetter@intel.com> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > > --- > > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > > include/drm/drm_connector.h | 2 ++ > > 2 files changed, 40 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > > index d4e852f..09f4093 100644 > > --- a/drivers/gpu/drm/drm_connector.c > > +++ b/drivers/gpu/drm/drm_connector.c > > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > } > > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > > > +/** > > + * drm_mode_connector_set_link_status_property - Set the link status property of > > + * a connector to indicate status of link as a result of link training. > > + * @connector: drm connector > > + * @link_status: new value of link status property (0: Good, 1: Bad) > > + * > > + * In usual working scenario, this link status property will always be set to > > + * "GOOD". > > + * If something fails during or after a mode set, the kernel driver can set this > > + * link status to "BAD", prune the mode list based on new information and send a > > + * hotplug uevent for userspace to have it re-check the valid modes through > > + * Get_connector and try again. > > + * > > + * If userspace is not aware of this property, the user experience is the same > > + * as it currently is. If the userspace is aware of the property, it has a chance > > + * to improve user experience by handling link training failures, avoiding black > > + * screens. The DRM driver can chose to not modify property and keep link status > > + * as "GOOD" always to keep the user experience same as it currently is. > > + * > > + * The reason for adding this property is to handle link training failures, but > > + * it is not limited to DP or link training. For example, if we implement > > + * asynchronous setcrtc, this property can be used to reportany failures in that. > > + * > > + * This function must be called from asynchronous work item. > > + * Returns zero on success and negative errrno on failure. > > + */ > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status) > > +{ > > + struct drm_device *dev = connector->dev; > > + > > + connector->link_status = link_status; > > + return drm_object_property_set_value(&connector->base, > > + dev->mode_config.link_status_property, > > + link_status); > > +} > > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > > + > > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > > struct drm_property *property, > > uint64_t value) > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > index ad5c8b0..ac76469 100644 > > --- a/include/drm/drm_connector.h > > +++ b/include/drm/drm_connector.h > > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > const struct edid *edid); > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status); > > > > /** > > * drm_for_each_connector - iterate over all connectors > > -- > > 1.9.1 > > > _______________________________________________ > dri-devel mailing list > dri-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/dri-devel
On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > In the usual working scenarios, this property is "Good". > If something fails during modeset, the DRM driver can > set the link status to "Bad", prune the mode list based on the > link rate/lane count fallback values and send hotplug uevent > so that userspace that is aware of this property can take an > appropriate action by reprobing connectors and re triggering > a modeset to improve user experience and avoid black screens. > In case of userspace that is not aware of this link status > property, the user experience will be unchanged. > > The reason for adding the property is to handle link training failures, > but it is not limited to DP or link training. For example, if we > implement asynchronous setcrtc, we can use this to report any failures > in that. > > Cc: dri-devel@lists.freedesktop.org > Cc: Jani Nikula <jani.nikula@linux.intel.com> > Cc: Daniel Vetter <daniel.vetter@intel.com> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> One more thing I've forgotten: Just adding the kernel-doc isn't enough yet, we need to link this new property into the overall property documentations. We already have a section "KMS Properties" in Documentation/gpu/drm-kms.rst, I think adding a new sub-section called "Standard Connector Properties" there with a definition list pointing to this function here would be best. -Daniel > --- > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > include/drm/drm_connector.h | 2 ++ > 2 files changed, 40 insertions(+) > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > index d4e852f..09f4093 100644 > --- a/drivers/gpu/drm/drm_connector.c > +++ b/drivers/gpu/drm/drm_connector.c > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > } > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > +/** > + * drm_mode_connector_set_link_status_property - Set the link status property of > + * a connector to indicate status of link as a result of link training. > + * @connector: drm connector > + * @link_status: new value of link status property (0: Good, 1: Bad) > + * > + * In usual working scenario, this link status property will always be set to > + * "GOOD". > + * If something fails during or after a mode set, the kernel driver can set this > + * link status to "BAD", prune the mode list based on new information and send a > + * hotplug uevent for userspace to have it re-check the valid modes through > + * Get_connector and try again. > + * > + * If userspace is not aware of this property, the user experience is the same > + * as it currently is. If the userspace is aware of the property, it has a chance > + * to improve user experience by handling link training failures, avoiding black > + * screens. The DRM driver can chose to not modify property and keep link status > + * as "GOOD" always to keep the user experience same as it currently is. > + * > + * The reason for adding this property is to handle link training failures, but > + * it is not limited to DP or link training. For example, if we implement > + * asynchronous setcrtc, this property can be used to reportany failures in that. > + * > + * This function must be called from asynchronous work item. > + * Returns zero on success and negative errrno on failure. > + */ > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status) > +{ > + struct drm_device *dev = connector->dev; > + > + connector->link_status = link_status; > + return drm_object_property_set_value(&connector->base, > + dev->mode_config.link_status_property, > + link_status); > +} > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > + > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > struct drm_property *property, > uint64_t value) > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > index ad5c8b0..ac76469 100644 > --- a/include/drm/drm_connector.h > +++ b/include/drm/drm_connector.h > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > const struct edid *edid); > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > + uint64_t link_status); > > /** > * drm_for_each_connector - iterate over all connectors > -- > 1.9.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
On Tue, Nov 15, 2016 at 08:49:21AM +0100, Daniel Vetter wrote: > On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > > In the usual working scenarios, this property is "Good". > > If something fails during modeset, the DRM driver can > > set the link status to "Bad", prune the mode list based on the > > link rate/lane count fallback values and send hotplug uevent > > so that userspace that is aware of this property can take an > > appropriate action by reprobing connectors and re triggering > > a modeset to improve user experience and avoid black screens. > > In case of userspace that is not aware of this link status > > property, the user experience will be unchanged. > > > > The reason for adding the property is to handle link training failures, > > but it is not limited to DP or link training. For example, if we > > implement asynchronous setcrtc, we can use this to report any failures > > in that. > > > > Cc: dri-devel@lists.freedesktop.org > > Cc: Jani Nikula <jani.nikula@linux.intel.com> > > Cc: Daniel Vetter <daniel.vetter@intel.com> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > > --- > > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > > include/drm/drm_connector.h | 2 ++ > > 2 files changed, 40 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > > index d4e852f..09f4093 100644 > > --- a/drivers/gpu/drm/drm_connector.c > > +++ b/drivers/gpu/drm/drm_connector.c > > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > } > > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > > > +/** > > + * drm_mode_connector_set_link_status_property - Set the link status property of > > + * a connector to indicate status of link as a result of link training. > > iirc this continuation upsets kernel-doc. Did you build the docs and > review them? You need to indent the 2nd line. > I built the docs and didnt see any issue with the docs, but I will shorten the description. > Also, might just shorten it to "set link status for a connector", details > are for the text below. > > > + * @connector: drm connector > > + * @link_status: new value of link status property (0: Good, 1: Bad) > > + * > > + * In usual working scenario, this link status property will always be set to > > + * "GOOD". > > Unecessary linebbreak. Either make a full paragraph (empty line) or > reflow, this here won't survivie kernel-doc formatting. > Agree, will fix this. > > + * If something fails during or after a mode set, the kernel driver can set this > > + * link status to "BAD", prune the mode list based on new information and send a > > First need to prune the mode list, then set the property. Please reorder > in your text. > > > + * hotplug uevent for userspace to have it re-check the valid modes through > > + * Get_connector and try again. > > s/Get_connector/GET_CONNECTOR IOCTL/ is the more usual style. > > > + * > > + * If userspace is not aware of this property, the user experience is the same > > + * as it currently is. If the userspace is aware of the property, it has a chance > > + * to improve user experience by handling link training failures, avoiding black > > + * screens. The DRM driver can chose to not modify property and keep link status > > + * as "GOOD" always to keep the user experience same as it currently is. > > Imo this paragraph isn't needed. Maybe just mention that old userspace > exists: > I think keeping this paragraph is important to give the readers good idea of how this will affect the user experience. > "Note that a lot of existing userspace doesn't handle this property. > Drivers can therefore not rely on userspace to fix up everything and > should try to handle issues (like just re-training a link) without > userspace's intervention. This should only be used when the current mode > doesn't work any more, and userspace must select a different display > mode." > But atleast the way i915 uses this is in both cases where current mode does not get pruned but need sto be retried and also when current mode is no longer valid and gets pruned and modeset is done at a lower mode. But in either case if link training fails, this property is set to BAD. Manasi > > + * > > + * The reason for adding this property is to handle link training failures, but > > + * it is not limited to DP or link training. For example, if we implement > > + * asynchronous setcrtc, this property can be used to reportany failures in that. > > s/reportany/report/ > > > + * > > + * This function must be called from asynchronous work item. > > This isn't true - it doesn't require an asynchronous work item, but the > locking rules mean that it. > > > + * Returns zero on success and negative errrno on failure. > > Hm, why can this ever fail? Intuitively this should never fail, and hence > we shouldn't need an error return value. > Ok, yes agree will change it to return void. > > + */ > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status) > > +{ > > + struct drm_device *dev = connector->dev; > > + > > + connector->link_status = link_status; > > + return drm_object_property_set_value(&connector->base, > > + dev->mode_config.link_status_property, > > + link_status); > > This misses the hotplug_event call from my proposal. Intentionally? Why? > > Also: With the current code you require that mode_config.mutex is held by > the caller. Every time you add a library/core function which requires > certain locks to be held, please check that with something like > lockdep_assert_held or similar. Leaking locking rules to callers like this > should be the exception, not the rule. > > But with my proposal this function here would grab all necessary locks, > solving that problem, too. > -Daniel > As per our IRC chat, I am going to leave ueventc calling to the caller of this function. > > +} > > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > > + > > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > > struct drm_property *property, > > uint64_t value) > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > index ad5c8b0..ac76469 100644 > > --- a/include/drm/drm_connector.h > > +++ b/include/drm/drm_connector.h > > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > const struct edid *edid); > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status); > > > > /** > > * drm_for_each_connector - iterate over all connectors > > -- > > 1.9.1 > > > > _______________________________________________ > > Intel-gfx mailing list > > Intel-gfx@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
On Tue, Nov 15, 2016 at 08:53:27AM +0100, Daniel Vetter wrote: > On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > > In the usual working scenarios, this property is "Good". > > If something fails during modeset, the DRM driver can > > set the link status to "Bad", prune the mode list based on the > > link rate/lane count fallback values and send hotplug uevent > > so that userspace that is aware of this property can take an > > appropriate action by reprobing connectors and re triggering > > a modeset to improve user experience and avoid black screens. > > In case of userspace that is not aware of this link status > > property, the user experience will be unchanged. > > > > The reason for adding the property is to handle link training failures, > > but it is not limited to DP or link training. For example, if we > > implement asynchronous setcrtc, we can use this to report any failures > > in that. > > > > Cc: dri-devel@lists.freedesktop.org > > Cc: Jani Nikula <jani.nikula@linux.intel.com> > > Cc: Daniel Vetter <daniel.vetter@intel.com> > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > > One more thing I've forgotten: Just adding the kernel-doc isn't enough > yet, we need to link this new property into the overall property > documentations. > > We already have a section "KMS Properties" in > Documentation/gpu/drm-kms.rst, I think adding a new sub-section called > "Standard Connector Properties" there with a definition list pointing to > this function here would be best. > -Daniel > What about other standard proprties like EDID etc? And could you give an example for writing out a definition list there pointing to this function? This .rst file currently consists of kernel::doc:: and paths for .h files Manasi > > --- > > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > > include/drm/drm_connector.h | 2 ++ > > 2 files changed, 40 insertions(+) > > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > > index d4e852f..09f4093 100644 > > --- a/drivers/gpu/drm/drm_connector.c > > +++ b/drivers/gpu/drm/drm_connector.c > > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > } > > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > > > +/** > > + * drm_mode_connector_set_link_status_property - Set the link status property of > > + * a connector to indicate status of link as a result of link training. > > + * @connector: drm connector > > + * @link_status: new value of link status property (0: Good, 1: Bad) > > + * > > + * In usual working scenario, this link status property will always be set to > > + * "GOOD". > > + * If something fails during or after a mode set, the kernel driver can set this > > + * link status to "BAD", prune the mode list based on new information and send a > > + * hotplug uevent for userspace to have it re-check the valid modes through > > + * Get_connector and try again. > > + * > > + * If userspace is not aware of this property, the user experience is the same > > + * as it currently is. If the userspace is aware of the property, it has a chance > > + * to improve user experience by handling link training failures, avoiding black > > + * screens. The DRM driver can chose to not modify property and keep link status > > + * as "GOOD" always to keep the user experience same as it currently is. > > + * > > + * The reason for adding this property is to handle link training failures, but > > + * it is not limited to DP or link training. For example, if we implement > > + * asynchronous setcrtc, this property can be used to reportany failures in that. > > + * > > + * This function must be called from asynchronous work item. > > + * Returns zero on success and negative errrno on failure. > > + */ > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status) > > +{ > > + struct drm_device *dev = connector->dev; > > + > > + connector->link_status = link_status; > > + return drm_object_property_set_value(&connector->base, > > + dev->mode_config.link_status_property, > > + link_status); > > +} > > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > > + > > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > > struct drm_property *property, > > uint64_t value) > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > index ad5c8b0..ac76469 100644 > > --- a/include/drm/drm_connector.h > > +++ b/include/drm/drm_connector.h > > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > const struct edid *edid); > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > + uint64_t link_status); > > > > /** > > * drm_for_each_connector - iterate over all connectors > > -- > > 1.9.1 > > > > _______________________________________________ > > Intel-gfx mailing list > > Intel-gfx@lists.freedesktop.org > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx > > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
On Tue, Nov 15, 2016 at 05:13:43PM -0800, Manasi Navare wrote: > On Tue, Nov 15, 2016 at 08:53:27AM +0100, Daniel Vetter wrote: > > On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > > > In the usual working scenarios, this property is "Good". > > > If something fails during modeset, the DRM driver can > > > set the link status to "Bad", prune the mode list based on the > > > link rate/lane count fallback values and send hotplug uevent > > > so that userspace that is aware of this property can take an > > > appropriate action by reprobing connectors and re triggering > > > a modeset to improve user experience and avoid black screens. > > > In case of userspace that is not aware of this link status > > > property, the user experience will be unchanged. > > > > > > The reason for adding the property is to handle link training failures, > > > but it is not limited to DP or link training. For example, if we > > > implement asynchronous setcrtc, we can use this to report any failures > > > in that. > > > > > > Cc: dri-devel@lists.freedesktop.org > > > Cc: Jani Nikula <jani.nikula@linux.intel.com> > > > Cc: Daniel Vetter <daniel.vetter@intel.com> > > > Cc: Ville Syrjala <ville.syrjala@linux.intel.com> > > > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> > > > > One more thing I've forgotten: Just adding the kernel-doc isn't enough > > yet, we need to link this new property into the overall property > > documentations. > > > > We already have a section "KMS Properties" in > > Documentation/gpu/drm-kms.rst, I think adding a new sub-section called > > "Standard Connector Properties" there with a definition list pointing to > > this function here would be best. > > -Daniel > > > > What about other standard proprties like EDID etc? And could you give an > example for writing out a definition list there pointing to this function? > This .rst file currently consists of kernel::doc:: and paths for .h files Yeah, none of the standard connector properties are currently documented. I'll write a quick patch that you can then base yours on. -Daniel > > Manasi > > > --- > > > drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ > > > include/drm/drm_connector.h | 2 ++ > > > 2 files changed, 40 insertions(+) > > > > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > > > index d4e852f..09f4093 100644 > > > --- a/drivers/gpu/drm/drm_connector.c > > > +++ b/drivers/gpu/drm/drm_connector.c > > > @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > > } > > > EXPORT_SYMBOL(drm_mode_connector_update_edid_property); > > > > > > +/** > > > + * drm_mode_connector_set_link_status_property - Set the link status property of > > > + * a connector to indicate status of link as a result of link training. > > > + * @connector: drm connector > > > + * @link_status: new value of link status property (0: Good, 1: Bad) > > > + * > > > + * In usual working scenario, this link status property will always be set to > > > + * "GOOD". > > > + * If something fails during or after a mode set, the kernel driver can set this > > > + * link status to "BAD", prune the mode list based on new information and send a > > > + * hotplug uevent for userspace to have it re-check the valid modes through > > > + * Get_connector and try again. > > > + * > > > + * If userspace is not aware of this property, the user experience is the same > > > + * as it currently is. If the userspace is aware of the property, it has a chance > > > + * to improve user experience by handling link training failures, avoiding black > > > + * screens. The DRM driver can chose to not modify property and keep link status > > > + * as "GOOD" always to keep the user experience same as it currently is. > > > + * > > > + * The reason for adding this property is to handle link training failures, but > > > + * it is not limited to DP or link training. For example, if we implement > > > + * asynchronous setcrtc, this property can be used to reportany failures in that. > > > + * > > > + * This function must be called from asynchronous work item. > > > + * Returns zero on success and negative errrno on failure. > > > + */ > > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > > + uint64_t link_status) > > > +{ > > > + struct drm_device *dev = connector->dev; > > > + > > > + connector->link_status = link_status; > > > + return drm_object_property_set_value(&connector->base, > > > + dev->mode_config.link_status_property, > > > + link_status); > > > +} > > > +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); > > > + > > > int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, > > > struct drm_property *property, > > > uint64_t value) > > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > > index ad5c8b0..ac76469 100644 > > > --- a/include/drm/drm_connector.h > > > +++ b/include/drm/drm_connector.h > > > @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, > > > int drm_mode_connector_set_tile_property(struct drm_connector *connector); > > > int drm_mode_connector_update_edid_property(struct drm_connector *connector, > > > const struct edid *edid); > > > +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, > > > + uint64_t link_status); > > > > > > /** > > > * drm_for_each_connector - iterate over all connectors > > > -- > > > 1.9.1 > > > > > > _______________________________________________ > > > Intel-gfx mailing list > > > Intel-gfx@lists.freedesktop.org > > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx > > > > -- > > Daniel Vetter > > Software Engineer, Intel Corporation > > http://blog.ffwll.ch
On Tue, Nov 15, 2016 at 03:56:09PM -0800, Manasi Navare wrote: > On Tue, Nov 15, 2016 at 08:49:21AM +0100, Daniel Vetter wrote: > > On Mon, Nov 14, 2016 at 07:13:20PM -0800, Manasi Navare wrote: > > > + * If userspace is not aware of this property, the user experience is the same > > > + * as it currently is. If the userspace is aware of the property, it has a chance > > > + * to improve user experience by handling link training failures, avoiding black > > > + * screens. The DRM driver can chose to not modify property and keep link status > > > + * as "GOOD" always to keep the user experience same as it currently is. > > > > Imo this paragraph isn't needed. Maybe just mention that old userspace > > exists: > > > > I think keeping this paragraph is important to give the readers good idea of how this > will affect the user experience. Well generally the kernel is _really_ far away from the user experience. I guess that's what makes this paragraph look strange to me, and why I reworded it. Generally the next thing that matters from the kernel pov is the compositor and it's display driver, hence why I used "userspace" instead of "user experience". What userspace (the code) is supposed to do is imo really important for new uabi, what the user experience ends up being, that depends upon the entire stack (of which we control very little, e.g. on Xorg we'll only send a hotplug event over Xrandr and let some desktop thing handle the real mode change), and it's also fairly abstract. > > "Note that a lot of existing userspace doesn't handle this property. > > Drivers can therefore not rely on userspace to fix up everything and > > should try to handle issues (like just re-training a link) without > > userspace's intervention. This should only be used when the current mode > > doesn't work any more, and userspace must select a different display > > mode." > > > > But atleast the way i915 uses this is in both cases where current mode > does not get pruned but need sto be retried and also when current mode > is no longer valid and gets pruned and modeset is done at a lower mode. > But in either case if link training fails, this property is set to BAD. Yeah, hence "should" and not "must", and even i915 does handle some situations itself: E.g. if just retraining works out with different training settings, then we don't need to involve userspace, despite that the link went bad for a bit. -Daniel
diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index d4e852f..09f4093 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -968,6 +968,44 @@ int drm_mode_connector_update_edid_property(struct drm_connector *connector, } EXPORT_SYMBOL(drm_mode_connector_update_edid_property); +/** + * drm_mode_connector_set_link_status_property - Set the link status property of + * a connector to indicate status of link as a result of link training. + * @connector: drm connector + * @link_status: new value of link status property (0: Good, 1: Bad) + * + * In usual working scenario, this link status property will always be set to + * "GOOD". + * If something fails during or after a mode set, the kernel driver can set this + * link status to "BAD", prune the mode list based on new information and send a + * hotplug uevent for userspace to have it re-check the valid modes through + * Get_connector and try again. + * + * If userspace is not aware of this property, the user experience is the same + * as it currently is. If the userspace is aware of the property, it has a chance + * to improve user experience by handling link training failures, avoiding black + * screens. The DRM driver can chose to not modify property and keep link status + * as "GOOD" always to keep the user experience same as it currently is. + * + * The reason for adding this property is to handle link training failures, but + * it is not limited to DP or link training. For example, if we implement + * asynchronous setcrtc, this property can be used to reportany failures in that. + * + * This function must be called from asynchronous work item. + * Returns zero on success and negative errrno on failure. + */ +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, + uint64_t link_status) +{ + struct drm_device *dev = connector->dev; + + connector->link_status = link_status; + return drm_object_property_set_value(&connector->base, + dev->mode_config.link_status_property, + link_status); +} +EXPORT_SYMBOL(drm_mode_connector_set_link_status_property); + int drm_mode_connector_set_obj_prop(struct drm_mode_object *obj, struct drm_property *property, uint64_t value) diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index ad5c8b0..ac76469 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -778,6 +778,8 @@ int drm_mode_connector_set_path_property(struct drm_connector *connector, int drm_mode_connector_set_tile_property(struct drm_connector *connector); int drm_mode_connector_update_edid_property(struct drm_connector *connector, const struct edid *edid); +int drm_mode_connector_set_link_status_property(struct drm_connector *connector, + uint64_t link_status); /** * drm_for_each_connector - iterate over all connectors
In the usual working scenarios, this property is "Good". If something fails during modeset, the DRM driver can set the link status to "Bad", prune the mode list based on the link rate/lane count fallback values and send hotplug uevent so that userspace that is aware of this property can take an appropriate action by reprobing connectors and re triggering a modeset to improve user experience and avoid black screens. In case of userspace that is not aware of this link status property, the user experience will be unchanged. The reason for adding the property is to handle link training failures, but it is not limited to DP or link training. For example, if we implement asynchronous setcrtc, we can use this to report any failures in that. Cc: dri-devel@lists.freedesktop.org Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Ville Syrjala <ville.syrjala@linux.intel.com> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com> --- drivers/gpu/drm/drm_connector.c | 38 ++++++++++++++++++++++++++++++++++++++ include/drm/drm_connector.h | 2 ++ 2 files changed, 40 insertions(+)