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@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Ville Syrjala <ville.syrjala@xxxxxxxxxxxxxxx>
> > Signed-off-by: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> > ---
> > 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
> >
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--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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