On Fri, Oct 12, 2018 at 11:42:32AM -0700, Radhakrishna Sripada wrote:
> At times 12bpc HDMI cannot be driven due to faulty cables, dongles
> level shifters etc. To workaround them we may need to drive the output
> at a lower bpc. Currently the user space does not have a way to limit
> the bpc. The default bpc to be programmed is decided by the driver and
> is run against connector limitations.
> 
> Creating a new connector property "max bpc" in order to limit the bpc.
> xrandr can make use of this connector property to make sure that bpc does
> not exceed the configured value. This property can be used by userspace to
> set the bpc.
> 
> V2: Initialize max_bpc to satisfy kms_properties
> V3: Move the property to drm_connector
> V4: Split drm and i915 components(Ville)
> V5: Make the property per connector(Ville)
> V6: Compare the requested bpc to connector bpc(Daniel)
>     Move the attach_property function to core(Ville)
> V7: Fix checkpatch warnings
> V8: Simplify the connector check code(Ville)
> V9: Const display_info(Ville)
> V10,V11: Fix CI issues.
> V12: Add the Kernel documentation(Daniel)
> V14: Crossreference the function name in the doc(Daniel)
> 
> Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Cc: Daniel Vetter <daniel.vet...@ffwll.ch>
> Cc: Kishore Kadiyala <kishore.kadiy...@intel.com>
> Cc: Rodrigo Vivi <rodrigo.v...@intel.com>
> Cc: Manasi Navare <manasi.d.nav...@intel.com>
> Cc: Stanislav Lisovskiy <stanislav.lisovs...@intel.com>
> Cc: Sunpeng Li <sunpeng...@amd.com>
> Acked-by: Daniel Vetter <daniel.vet...@ffwll.ch>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.srip...@intel.com>

This patch looks right to me:

Reviewed-by: Rodrigo Vivi <rodrigo.v...@intel.com>

but we probably need to hold on merge while we wait clarifications
and final rv-b on igt tests....

> ---
>  drivers/gpu/drm/drm_atomic.c        |  5 +++++
>  drivers/gpu/drm/drm_atomic_helper.c |  4 ++++
>  drivers/gpu/drm/drm_atomic_uapi.c   |  4 ++++
>  drivers/gpu/drm/drm_connector.c     | 41 
> +++++++++++++++++++++++++++++++++++++
>  include/drm/drm_connector.h         | 20 ++++++++++++++++++
>  5 files changed, 74 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 2870ae205237..cd8362dc4f74 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -390,6 +390,11 @@ static int drm_atomic_connector_check(struct 
> drm_connector *connector,
>  {
>       struct drm_crtc_state *crtc_state;
>       struct drm_writeback_job *writeback_job = state->writeback_job;
> +     const struct drm_display_info *info = &connector->display_info;
> +
> +     state->max_bpc = info->bpc ? info->bpc : 8;
> +     if (connector->max_bpc_property)
> +             state->max_bpc = min(state->max_bpc, state->max_requested_bpc);
>  
>       if ((connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK) || 
> !writeback_job)
>               return 0;
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c 
> b/drivers/gpu/drm/drm_atomic_helper.c
> index 6f66777dca4b..d61a74b254f5 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -650,6 +650,10 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
>                       if (old_connector_state->link_status !=
>                           new_connector_state->link_status)
>                               new_crtc_state->connectors_changed = true;
> +
> +                     if (old_connector_state->max_requested_bpc !=
> +                         new_connector_state->max_requested_bpc)
> +                             new_crtc_state->connectors_changed = true;
>               }
>  
>               if (funcs->atomic_check)
> diff --git a/drivers/gpu/drm/drm_atomic_uapi.c 
> b/drivers/gpu/drm/drm_atomic_uapi.c
> index a22d6f269b07..7492819c81ce 100644
> --- a/drivers/gpu/drm/drm_atomic_uapi.c
> +++ b/drivers/gpu/drm/drm_atomic_uapi.c
> @@ -761,6 +761,8 @@ static int drm_atomic_connector_set_property(struct 
> drm_connector *connector,
>  
>               return set_out_fence_for_connector(state->state, connector,
>                                                  fence_ptr);
> +     } else if (property == connector->max_bpc_property) {
> +             state->max_requested_bpc = val;
>       } else if (connector->funcs->atomic_set_property) {
>               return connector->funcs->atomic_set_property(connector,
>                               state, property, val);
> @@ -825,6 +827,8 @@ drm_atomic_connector_get_property(struct drm_connector 
> *connector,
>               *val = 0;
>       } else if (property == config->writeback_out_fence_ptr_property) {
>               *val = 0;
> +     } else if (property == connector->max_bpc_property) {
> +             *val = state->max_requested_bpc;
>       } 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 5d01414ec9f7..bdaa29e530d4 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -932,6 +932,13 @@ DRM_ENUM_NAME_FN(drm_get_content_protection_name, 
> drm_cp_enum_list)
>   *     is no longer protected and userspace should take appropriate action
>   *     (whatever that might be).
>   *
> + * max bpc:
> + *   This range property is used by userspace to limit the bit depth. When
> + *   used the driver would limit the bpc in accordance with the valid range
> + *   supported by the hardware and sink. Drivers to use the function
> + *   drm_connector_attach_max_bpc_property() to create and attach the
> + *   property to the connector during initialization.
> + *
>   * Connectors also have one standardized atomic property:
>   *
>   * CRTC_ID:
> @@ -1600,6 +1607,40 @@ void drm_connector_set_link_status_property(struct 
> drm_connector *connector,
>  EXPORT_SYMBOL(drm_connector_set_link_status_property);
>  
>  /**
> + * drm_connector_attach_max_bpc_property - attach "max bpc" property
> + * @connector: connector to attach max bpc property on.
> + * @min: The minimum bit depth supported by the connector.
> + * @max: The maximum bit depth supported by the connector.
> + *
> + * This is used to add support for limiting the bit depth on a connector.
> + *
> + * Returns:
> + * Zero on success, negative errno on failure.
> + */
> +int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> +                                       int min, int max)
> +{
> +     struct drm_device *dev = connector->dev;
> +     struct drm_property *prop;
> +
> +     prop = connector->max_bpc_property;
> +     if (!prop) {
> +             prop = drm_property_create_range(dev, 0, "max bpc", min, max);
> +             if (!prop)
> +                     return -ENOMEM;
> +
> +             connector->max_bpc_property = prop;
> +     }
> +
> +     drm_object_attach_property(&connector->base, prop, max);
> +     connector->state->max_requested_bpc = max;
> +     connector->state->max_bpc = max;
> +
> +     return 0;
> +}
> +EXPORT_SYMBOL(drm_connector_attach_max_bpc_property);
> +
> +/**
>   * drm_connector_init_panel_orientation_property -
>   *   initialize the connecters panel_orientation property
>   * @connector: connector for which to init the panel-orientation property.
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 5b3cf909fd5e..a402d16427a1 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -461,6 +461,18 @@ struct drm_connector_state {
>        * drm_writeback_signal_completion()
>        */
>       struct drm_writeback_job *writeback_job;
> +
> +     /**
> +      * @max_requested_bpc: Connector property to limit the maximum bit
> +      * depth of the pixels.
> +      */
> +     u8 max_requested_bpc;
> +
> +     /**
> +      * @max_bpc: Connector max_bpc based on the requested max_bpc property
> +      * and the connector bpc limitations obtained from edid.
> +      */
> +     u8 max_bpc;
>  };
>  
>  /**
> @@ -924,6 +936,12 @@ struct drm_connector {
>        */
>       struct drm_property_blob *path_blob_ptr;
>  
> +     /**
> +      * @max_bpc_property: Default connector property for the max bpc to be
> +      * driven out of the connector.
> +      */
> +     struct drm_property *max_bpc_property;
> +
>  #define DRM_CONNECTOR_POLL_HPD (1 << 0)
>  #define DRM_CONNECTOR_POLL_CONNECT (1 << 1)
>  #define DRM_CONNECTOR_POLL_DISCONNECT (1 << 2)
> @@ -1202,6 +1220,8 @@ void drm_connector_set_link_status_property(struct 
> drm_connector *connector,
>                                           uint64_t link_status);
>  int drm_connector_init_panel_orientation_property(
>       struct drm_connector *connector, int width, int height);
> +int drm_connector_attach_max_bpc_property(struct drm_connector *connector,
> +                                       int min, int max);
>  
>  /**
>   * struct drm_tile_group - Tile group metadata
> -- 
> 2.9.3
> 
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> intel-...@lists.freedesktop.org
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