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)

Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: Daniel Vetter daniel.vetter@ffwll.ch 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 Cc: Sunpeng Li sunpeng.li@amd.com Acked-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Radhakrishna Sripada radhakrishna.sripada@intel.com --- 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 | 39 +++++++++++++++++++++++++++++++++++++ include/drm/drm_connector.h | 20 +++++++++++++++++++ 5 files changed, 72 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 e6a2cf72de5e..8bc919e3b271 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -669,6 +669,10 @@ 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 d5b7f315098c..86ac33922b09 100644 --- a/drivers/gpu/drm/drm_atomic_uapi.c +++ b/drivers/gpu/drm/drm_atomic_uapi.c @@ -740,6 +740,8 @@ 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); @@ -804,6 +806,8 @@ 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..a346004a1c4f 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -932,6 +932,11 @@ 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. + * * Connectors also have one standardized atomic property: * * CRTC_ID: @@ -1600,6 +1605,40 @@ 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