+ Harry, Leo
This would definitely be useful. We ran into a lot of issues when we
enabled >8 bpc support.
On Tue, Sep 18, 2018 at 2:10 PM Radhakrishna Sripada
<radhakrishna.sripada@xxxxxxxxx> 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)
>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> 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 | 5 +++++
> drivers/gpu/drm/drm_atomic_helper.c | 4 ++++
> drivers/gpu/drm/drm_atomic_uapi.c | 4 ++++
> drivers/gpu/drm/drm_connector.c | 33 +++++++++++++++++++++++++++++++++
> include/drm/drm_connector.h | 20 ++++++++++++++++++++
> 5 files changed, 66 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 2870ae205237..dc76e89c04af 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -390,6 +390,7 @@ 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;
> + struct drm_display_info *info = &connector->display_info;
>
> if ((connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK) || !writeback_job)
> return 0;
> @@ -417,6 +418,10 @@ static int drm_atomic_connector_check(struct drm_connector *connector,
> return -EINVAL;
> }
>
> + state->max_bpc = info->bpc ?: 8;
> + if (connector->max_bpc_property)
> + state->max_bpc = min(state->max_bpc, state->max_requested_bpc);
> +
> return 0;
> }
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index 3cf1aa132778..d9ce8077fb6a 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -639,6 +639,10 @@ 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 1e40e5decbe9..65e22c1b37a5 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -1583,6 +1583,39 @@ 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;
> +
> + 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 91a877fa00cb..bfc3e698cda6 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)
> @@ -1201,6 +1219,8 @@ 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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