From: Derek Foreman <[email protected]> Add a way to know the actual bpc of a running link.
Drivers might change the current bpc link value due to changes in mode line or refresh rates. An example can be found when switching the color output format, part of YUV420 fallback. This means we might be displaying a stale bpc value although it was modified for different reasons -- like a refresh rate or an output color format. Introduces a new property 'link bpc' that user-space can use to get the current bpc value of a running link while in the same time allow user-space to set-up bpc using 'max bpc' property. An implementation for Weston [1] and a simple test for i-g-t [2] have been added. Signed-off-by: Derek Foreman <[email protected]> Signed-off-by: Marius Vlad <[email protected]> [1] https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1850 [2] https://lists.freedesktop.org/archives/igt-dev/2025-October/097061.html Signed-off-by: Marius Vlad <[email protected]> --- v1: - https://lore.kernel.org/dri-devel/[email protected]/T/#u v2: - replace return with EBUSY if connector already exists (Dmitry) - add i-g-t test and an implementation for Weston (Dmitry) - re-wording patch description (Jani) - https://lore.kernel.org/dri-devel/[email protected]/ v3: - remove VRR mention from commit description (Ville) - add DRM_MODE_PROP_IMMUTABLE to flags (Ville) - provide helpers functions for drivers to use (can be used by other types of connectors, not just HDMI) - send uevent informating userspace when 'link bpc' connector state changed (Daniel @ https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1850) - added missing doc entry .../gpu/drm/display/drm_hdmi_state_helper.c | 3 + drivers/gpu/drm/drm_atomic_uapi.c | 2 + drivers/gpu/drm/drm_connector.c | 125 ++++++++++++++++++ include/drm/drm_connector.h | 32 +++++ 4 files changed, 162 insertions(+) diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c index a561f124be99..a728b43bdf05 100644 --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c @@ -866,6 +866,9 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector, crtc_state->mode_changed = true; } + drm_connector_update_link_bpc_state(connector, + new_conn_state->hdmi.output_bpc); + return 0; } EXPORT_SYMBOL(drm_atomic_helper_connector_hdmi_check); diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c index 85dbdaa4a2e2..ab43ffcc6c71 100644 --- a/drivers/gpu/drm/drm_atomic_uapi.c +++ b/drivers/gpu/drm/drm_atomic_uapi.c @@ -865,6 +865,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector, *val = state->privacy_screen_sw_state; } else if (property == connector->broadcast_rgb_property) { *val = state->hdmi.broadcast_rgb; + } else if (property == connector->link_bpc_property) { + *val = state->link_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 272d6254ea47..4eca0d9c0a97 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -87,6 +87,28 @@ struct drm_conn_prop_enum_list { struct ida ida; }; +static void +link_bpc_wq_callback(struct work_struct *work) +{ + struct delayed_work *dwork; + struct link_bpc_wq *link_bpc; + struct drm_connector *connector; + struct drm_device *drm_dev; + + dwork = to_delayed_work(work); + link_bpc = container_of(dwork, struct link_bpc_wq, d_work); + connector = container_of(link_bpc, struct drm_connector, link_bpc); + drm_dev = connector->dev; + + drm_modeset_lock(&drm_dev->mode_config.connection_mutex, NULL); + mutex_lock(&connector->link_bpc.lock); + + drm_connector_update_link_bpc_property(connector); + + mutex_unlock(&connector->link_bpc.lock); + drm_modeset_unlock(&drm_dev->mode_config.connection_mutex); +} + /* * Connector and encoder types. */ @@ -292,6 +314,14 @@ static int drm_connector_init_only(struct drm_device *dev, connector->display_info.panel_orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN; + mutex_init(&connector->link_bpc.lock); + INIT_DELAYED_WORK(&connector->link_bpc.d_work, link_bpc_wq_callback); + connector->link_bpc.wq = create_workqueue("link bpc workqueue"); + if (!connector->link_bpc.wq) { + dev_err(dev->dev, "Failed to create work queue\n"); + return -ENOMEM; + } + drm_connector_get_cmdline_mode(connector); if (connector_type != DRM_MODE_CONNECTOR_VIRTUAL && @@ -542,6 +572,85 @@ int drmm_connector_init(struct drm_device *dev, } EXPORT_SYMBOL(drmm_connector_init); +/** + * drm_connector_attach_link_bpc_property - create and attach 'link bpc' property + * @connector: drm connector + * @max_bpc: specify the upper limit, matching that of 'max bpc' property + * + * Returns: + * Zero on success, error code on failure. + */ +int +drm_connector_attach_link_bpc_property(struct drm_connector *connector, + unsigned int max_bpc) +{ + struct drm_device *dev = connector->dev; + struct drm_property *prop; + + if (connector->link_bpc_property) + return -EBUSY; + + prop = drm_property_create_range(dev, DRM_MODE_PROP_IMMUTABLE, "link bpc", 8, max_bpc); + if (!prop) + return -ENOMEM; + + connector->link_bpc_property = prop; + + drm_object_attach_property(&connector->base, prop, max_bpc); + + return 0; +} +EXPORT_SYMBOL(drm_connector_attach_link_bpc_property); + +/** + * drm_connector_update_link_bpc_property - update the 'link bpc' property of a connector + * @connector: drm connector + * + * This sends a uevent to userspace to notify about the fact that 'link bpc' + * has been updated. + */ +void +drm_connector_update_link_bpc_property(struct drm_connector *connector) +{ + struct drm_connector_state *state = connector->state; + + if (!connector->link_bpc_property) + return; + + drm_dbg_kms(connector->dev, "[CONNECTOR:%d:%s] Setting state link bpc %u\n", + connector->base.id, connector->name, state->link_bpc); + drm_object_property_set_value(&connector->base, + connector->link_bpc_property, + state->link_bpc); + + drm_sysfs_connector_property_event(connector, + connector->link_bpc_property); +} +EXPORT_SYMBOL(drm_connector_update_link_bpc_property); + +/** + * drm_connector_update_link_bpc_state - update the 'link bpc' connector state + * @connector: drm connector + * @val: new value for the 'link bpc' property + * + */ +void +drm_connector_update_link_bpc_state(struct drm_connector *connector, u8 val) +{ + struct drm_connector_state *state = connector->state; + + if (!connector->link_bpc_property) + return; + + if (state->link_bpc == val) + return; + + state->link_bpc = val; + queue_delayed_work(connector->link_bpc.wq, + &connector->link_bpc.d_work, msecs_to_jiffies(1000)); +} +EXPORT_SYMBOL(drm_connector_update_link_bpc_state); + /** * drmm_connector_hdmi_init - Init a preallocated HDMI connector * @dev: DRM device @@ -618,6 +727,10 @@ int drmm_connector_hdmi_init(struct drm_device *dev, drm_connector_attach_max_bpc_property(connector, 8, max_bpc); connector->max_bpc = max_bpc; + ret = drm_connector_attach_link_bpc_property(connector, max_bpc); + if (ret) + return ret; + if (max_bpc > 8) drm_connector_attach_hdr_output_metadata_property(connector); @@ -802,6 +915,8 @@ void drm_connector_cleanup(struct drm_connector *connector) mutex_destroy(&connector->hdmi_audio.lock); mutex_destroy(&connector->hdmi.infoframes.lock); mutex_destroy(&connector->mutex); + mutex_destroy(&connector->link_bpc.lock); + destroy_workqueue(connector->link_bpc.wq); memset(connector, 0, sizeof(*connector)); @@ -1699,6 +1814,16 @@ EXPORT_SYMBOL(drm_hdmi_connector_get_output_format_name); * drm_connector_attach_max_bpc_property() to create and attach the * property to the connector during initialization. * + * link bpc: + * This immutable range property can be used by userspace to determine the + * current link bit depth. Drivers can use + * drm_connector_attach_link_bpc_property() to create and attach the + * property to the connector during initialization and + * drm_connector_update_link_bpc_state() to update the property and to + * queue an uevent with the new 'link bpc' value. + * Userspace can determine if the driver made bpc modifications by + * checking 'max bpc' against the 'link bpc' property. + * * Connectors also have one standardized atomic property: * * CRTC_ID: diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index 8f34f4b8183d..678875b1441b 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -1132,6 +1132,11 @@ struct drm_connector_state { */ u8 max_bpc; + /* + * @link_bpc: Current link bpc + */ + u8 link_bpc; + /** * @privacy_screen_sw_state: See :ref:`Standard Connector * Properties<standard_connector_properties>` @@ -1882,6 +1887,16 @@ struct drm_connector_cec { void *data; }; +/* + * struct link_bpc_wq - holds the necessary bits to queue uevents for + * propagating 'link bpc' connector updates + */ +struct link_bpc_wq { + struct workqueue_struct *wq; + struct delayed_work d_work; + struct mutex lock; +}; + /** * struct drm_connector - central DRM connector control structure * @@ -2079,6 +2094,19 @@ struct drm_connector { */ struct drm_property *max_bpc_property; + /** + * @link_bpc_property: Current connector link bpc set by the driver + * This property can be used to store the current link bpc. + */ + struct drm_property *link_bpc_property; + + /** + * @link_bpc_wq: workqueue for sending uevent to userspace with updated + * 'link bpc' value + */ + struct link_bpc_wq link_bpc; + + /** @privacy_screen: drm_privacy_screen for this connector, or NULL. */ struct drm_privacy_screen *privacy_screen; @@ -2488,6 +2516,10 @@ void drm_connector_attach_privacy_screen_provider( struct drm_connector *connector, struct drm_privacy_screen *priv); void drm_connector_update_privacy_screen(const struct drm_connector_state *connector_state); +int drm_connector_attach_link_bpc_property(struct drm_connector *connector, unsigned int max_bpc); +void drm_connector_update_link_bpc_property(struct drm_connector *connector); +void drm_connector_update_link_bpc_state(struct drm_connector *connector, u8 val); + /** * struct drm_tile_group - Tile group metadata * @refcount: reference count -- 2.47.2
