Re: [PATCH RFC] drm: Add a new connector atomic property for link status

[Manasi Navare <manasi.d.navare@intel.com>]

On Wed, Nov 23, 2016 at 11:00:59AM +0100, Daniel Vetter wrote:
> On Tue, Nov 22, 2016 at 05:30:21PM -0800, Manasi Navare wrote:
> > This is RFC patch for adding a connector link-status property
> > and making it atomic by adding it to the drm_connector_state.
> > This is to make sure its wired properly in drm_atomic_connector_set_property
> > and drm_atomic_connector_get_property functions.
> > 
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Daniel Vetter <daniel.vetter@intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > ---
> >  drivers/gpu/drm/drm_atomic.c    |  5 ++++
> >  drivers/gpu/drm/drm_connector.c | 65 +++++++++++++++++++++++++++++++++++++++--
> >  include/drm/drm_connector.h     | 12 +++++++-
> >  include/drm/drm_mode_config.h   |  5 ++++
> >  include/uapi/drm/drm_mode.h     |  4 +++
> >  5 files changed, 88 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> > index 89737e4..644d19f 100644
> > --- a/drivers/gpu/drm/drm_atomic.c
> > +++ b/drivers/gpu/drm/drm_atomic.c
> > @@ -1087,6 +1087,9 @@ int drm_atomic_connector_set_property(struct drm_connector *connector,
> >  		 * now?) atomic writes to DPMS property:
> >  		 */
> >  		return -EINVAL;
> > +	} else if (property == config->link_status_property) {
> > +		state->link_status = val;
> > +		return 0;
> >  	} else if (connector->funcs->atomic_set_property) {
> >  		return connector->funcs->atomic_set_property(connector,
> >  				state, property, val);
> > @@ -1135,6 +1138,8 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
> >  		*val = (state->crtc) ? state->crtc->base.id : 0;
> >  	} else if (property == config->dpms_property) {
> >  		*val = connector->dpms;
> > +	} else if (property == config->link_status_property) {
> > +		*val = state->link_status;
> >  	} else if (connector->funcs->atomic_get_property) {
> >  		return connector->funcs->atomic_get_property(connector,
> >  				state, property, val);
> > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> > index 5a45262..4576c9f 100644
> > --- a/drivers/gpu/drm/drm_connector.c
> > +++ b/drivers/gpu/drm/drm_connector.c
> > @@ -243,6 +243,10 @@ int drm_connector_init(struct drm_device *dev,
> >  	drm_object_attach_property(&connector->base,
> >  				      config->dpms_property, 0);
> >  
> > +	drm_object_attach_property(&connector->base,
> > +				   config->link_status_property,
> > +				   0);
> > +
> >  	if (drm_core_check_feature(dev, DRIVER_ATOMIC)) {
> >  		drm_object_attach_property(&connector->base, config->prop_crtc_id, 0);
> >  	}
> > @@ -506,6 +510,12 @@ const char *drm_get_subpixel_order_name(enum subpixel_order order)
> >  };
> >  DRM_ENUM_NAME_FN(drm_get_dpms_name, drm_dpms_enum_list)
> >  
> > +static const struct drm_prop_enum_list drm_link_status_enum_list[] = {
> > +	{ DRM_MODE_LINK_STATUS_GOOD, "Good" },
> > +	{ DRM_MODE_LINK_STATUS_BAD, "Bad" },
> > +};
> > +DRM_ENUM_NAME_FN(drm_get_link_status_name, drm_link_status_enum_list)
> > +
> >  /**
> >   * drm_display_info_set_bus_formats - set the supported bus formats
> >   * @info: display info to store bus formats in
> > @@ -616,7 +626,7 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	path property the MST manager created. Userspace cannot change this
> >   * 	property.
> >   * TILE:
> > - * 	Connector tile group property to indicate how a set of DRM connector
> > + *      Connector tile group property to indicate how a set of DRM connector
> >   * 	compose together into one logical screen. This is used by both high-res
> >   * 	external screens (often only using a single cable, but exposing multiple
> >   * 	DP MST sinks), or high-res integrated panels (like dual-link DSI) which
> > @@ -625,7 +635,14 @@ int drm_display_info_set_bus_formats(struct drm_display_info *info,
> >   * 	tiling and virtualize both &drm_crtc and &drm_plane if needed. Drivers
> >   * 	should update this value using drm_mode_connector_set_tile_property().
> >   * 	Userspace cannot change this property.
> > - *
> > + * link-status:
> > + *      Connector link-status property to indicate the status of link during
> > + *      the modeset. The default value of link-status is "GOOD". If something
> > + *      fails during modeset, the kernel driver can set this to "BAD", prune
> > + *      the mode list based on new link parameters and send a hotplug uevent
> > + *      to notify userspace to re-check the valid modes through GET_CONNECTOR
> > + *      IOCTL and redo a modeset. Drivers should update this value using
> > + *      drm_mode_connector_set_link_status_property().
> >   * Connectors also have one standardized atomic property:
> >   *
> >   * CRTC_ID:
> > @@ -666,6 +683,13 @@ int drm_connector_create_standard_properties(struct drm_device *dev)
> >  		return -ENOMEM;
> >  	dev->mode_config.tile_property = prop;
> >  
> > +	prop = drm_property_create_enum(dev, DRM_MODE_PROP_ATOMIC, "link-status",
> > +					drm_link_status_enum_list,
> > +					ARRAY_SIZE(drm_link_status_enum_list));
> > +	if (!prop)
> > +		return -ENOMEM;
> > +	dev->mode_config.link_status_property = prop;
> > +
> >  	return 0;
> >  }
> >  
> > @@ -995,6 +1019,43 @@ 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 link status property of a connector
> > + * @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 should
> > + * set this link status property to "BAD" and prune the mode list based on new
> > + * information. The caller then needs to send a hotplug uevent for userspace to
> > + *  re-check the valid modes through GET_CONNECTOR_IOCTL and retry modeset.
> > + *
> > + * Note that a lot of existing userspace do not 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
> > + * fails and userspace must select a different display mode.
> > + * 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 report any failures in that.
> > + */
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status)
> > +{
> > +	struct drm_device *dev = connector->dev;
> > +
> > +	/* Make sure the mutex is grabbed */
> > +	lockdep_assert_held(&dev->mode_config.mutex);
> 
> For atomic the lock we need is dev->mode_config.connection_mutex); Maybe
> we should just grab that here, from a quick check it shouldn't result in a
> deadlock.
>

So after grabing the connection mutex, do we still need the lockdep assert held for
mode_config.mutex?
This gets called from the work func that holds the mode-config.mutex, do we need to drop that
mutex then or is it okay to hold mode_config.mutex as well as connection mutex?

 
> > +	connector->link_status = link_status;
> 
> You need to set connector->state->link_status here for an atomic property.
>

Yes I need to set the connector state here. I will add that.
 
> > +	drm_object_property_set_value(&connector->base,
> > +				      dev->mode_config.link_status_property,
> > +				      link_status);
> 
> And this here isn't needed anymore with atomic.
>

So we no longer have the link_status property in mode_config struct?
All we have is the link_status in dmr_connector_state?

Manasi 
> > +}
> > +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 34f9741..3d513ab 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -213,6 +213,9 @@ struct drm_connector_state {
> >  
> >  	struct drm_encoder *best_encoder;
> >  
> > +	/* Connector Link status */
> > +	unsigned int link_status;
> 
> enum drm_link_status {
> 	DRM_LINK_STATUS_GOOD = DRM_MODE_LINK_STATUS_GOOD;
> 	DRM_LINK_STATUS_BAD = DRM_MODE_LINK_STATUS_GOOD;
> };
> 
> This way you don't need a comment explaing that 0 is good and 1 is bad.
> 
> > +
> >  	struct drm_atomic_state *state;
> >  };
> >  
> > @@ -695,6 +698,12 @@ struct drm_connector {
> >  	uint8_t num_h_tile, num_v_tile;
> >  	uint8_t tile_h_loc, tile_v_loc;
> >  	uint16_t tile_h_size, tile_v_size;
> > +
> > +	/* Connector Link status
> > +	 * 0: If the link is Good
> > +	 * 1: If the link is Bad
> > +	 */
> > +	int link_status;
> 
> This one needs to go, we don't want to duplicate this information.
> 
> >  };

This was added so we can easily grab this value within intel_dp functions,
or should those functions directly read the connector->state->link_sttaus?


> >  
> >  #define obj_to_connector(x) container_of(x, struct drm_connector, base)
> > @@ -767,12 +776,13 @@ int drm_mode_create_tv_properties(struct drm_device *dev,
> >  int drm_mode_create_scaling_mode_property(struct drm_device *dev);
> >  int drm_mode_create_aspect_ratio_property(struct drm_device *dev);
> >  int drm_mode_create_suggested_offset_properties(struct drm_device *dev);
> > -
> >  int drm_mode_connector_set_path_property(struct drm_connector *connector,
> >  					 const char *path);
> >  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);
> > +void drm_mode_connector_set_link_status_property(struct drm_connector *connector,
> > +						 uint64_t link_status);
> >  
> >  /**
> >   * struct drm_tile_group - Tile group metadata
> > diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> > index bf9991b..86faee4 100644
> > --- a/include/drm/drm_mode_config.h
> > +++ b/include/drm/drm_mode_config.h
> > @@ -431,6 +431,11 @@ struct drm_mode_config {
> >  	 */
> >  	struct drm_property *tile_property;
> >  	/**
> > +	 * @link_status_property: Default connector property for link status
> > +	 * of a connector
> > +	 */
> > +	struct drm_property *link_status_property;
> > +	/**
> >  	 * @plane_type_property: Default plane property to differentiate
> >  	 * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
> >  	 */
> > diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
> > index 728790b..309c478 100644
> > --- a/include/uapi/drm/drm_mode.h
> > +++ b/include/uapi/drm/drm_mode.h
> > @@ -123,6 +123,10 @@
> >  #define DRM_MODE_DIRTY_ON       1
> >  #define DRM_MODE_DIRTY_ANNOTATE 2
> >  
> > +/* Link Status options */
> > +#define DRM_MODE_LINK_STATUS_GOOD	0
> > +#define DRM_MODE_LINK_STATUS_BAD	1
> 
> The change to reset link_status to good for SETCRTC seems to be missing.
> Something like the below (totally untested) should get the job done.
> 
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 494680c9056e..5f47049d611e 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -2258,6 +2258,8 @@ static int update_output_state(struct drm_atomic_state *state,
>  								NULL);
>  			if (ret)
>  				return ret;
> +
> +			conn_state->link_status = DRM_LINK_STATUS_GOOD;
>  		}
>  	}
>  
> Small exercise for you: Follow the call chain of this function and figure
> out how it works. And let's hope I did it right and it does work ;-)
> 
> Cheers, Daniel
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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