On Thu, Aug 30, 2018 at 08:06:48AM -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)
>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Kishore Kadiyala <kishore.kadiyala@xxxxxxxxx>
> Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> Cc: Manasi Navare <manasi.d.navare@xxxxxxxxx>
> Cc: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic.c | 4 ++++
> drivers/gpu/drm/drm_atomic_helper.c | 4 ++++
> include/drm/drm_connector.h | 6 ++++++
> include/drm/drm_mode_config.h | 5 +++++
> 4 files changed, 19 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index d0478abc01bd..4e352fc1f0a0 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1420,6 +1420,8 @@ 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 == config->max_bpc_property) {
> + state->max_bpc = val;
> } else if (connector->funcs->atomic_set_property) {
> return connector->funcs->atomic_set_property(connector,
> state, property, val);
> @@ -1515,6 +1517,8 @@ 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 == config->max_bpc_property) {
> + *val = state->max_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_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 2c23a48482da..7f763650a623 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -638,6 +638,10 @@ 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_bpc !=
> + new_connector_state->max_bpc)
> + new_crtc_state->connectors_changed = true;
> }
>
> if (funcs->atomic_check)
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 97ea41dc678f..fc11f40aae51 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -460,6 +460,12 @@ struct drm_connector_state {
> * drm_writeback_signal_completion()
> */
> struct drm_writeback_job *writeback_job;
> +
> + /**
> + * @max_bpc: Connector property to limit the maximum bit depth of
> + * the pixels.
> + */
> + unsigned int max_bpc;
> };
>
> /**
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index a0b202e1d69a..b9cd7a73b244 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -562,6 +562,11 @@ struct drm_mode_config {
> */
> struct drm_property *link_status_property;
> /**
> + * @max_bpc_property: Default connector property for the max bpc to be
> + * driven out of the connector.
> + */
> + struct drm_property *max_bpc_property;
If we want the exposed limits to be accurate this needs to be
per-connector. The other option of course is to just expose the
global min-max range for the entire device.
The way you wrote the i915 bits suggest you wanted to go for
the per-connector apporach instead.
> + /**
> * @plane_type_property: Default plane property to differentiate
> * CURSOR, PRIMARY and OVERLAY legacy uses of planes.
> */
> --
> 2.9.3
--
Ville Syrjälä
Intel
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