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@linux.intel.com Cc: Kishore Kadiyala kishore.kadiyala@intel.com Cc: Rodrigo Vivi rodrigo.vivi@intel.com Cc: Manasi Navare manasi.d.navare@intel.com Cc: Stanislav Lisovskiy stanislav.lisovskiy@intel.com Signed-off-by: Radhakrishna Sripada radhakrishna.sripada@intel.com --- 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; + /** * @plane_type_property: Default plane property to differentiate * CURSOR, PRIMARY and OVERLAY legacy uses of planes. */