Re: [PATCH v3 1/2] drm: drm/i915: Add connector property to limit max bpc

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Aug 24, 2018 at 06:02:16PM -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
> with which the pixels are scanned out. 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
> 
> 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 ++++
>  drivers/gpu/drm/i915/intel_drv.h    |  2 ++
>  drivers/gpu/drm/i915/intel_hdmi.c   | 11 +++++++++++
>  drivers/gpu/drm/i915/intel_modes.c  | 20 ++++++++++++++++++++

Pls move all the i915 stuff to the second patch.

>  include/drm/drm_connector.h         |  6 ++++++
>  include/drm/drm_mode_config.h       |  5 +++++
>  7 files changed, 52 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index 3eb061e11e2e..461dde0c2c10 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1416,6 +1416,8 @@ 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);
> @@ -1511,6 +1513,8 @@ 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 38ce9a375ffb..82caac8d1432 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/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 1b78de838c18..209eb1798238 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1862,6 +1862,8 @@ int intel_ddc_get_modes(struct drm_connector *c, struct i2c_adapter *adapter);
>  void intel_attach_force_audio_property(struct drm_connector *connector);
>  void intel_attach_broadcast_rgb_property(struct drm_connector *connector);
>  void intel_attach_aspect_ratio_property(struct drm_connector *connector);
> +void intel_attach_max_bpc_property(struct drm_connector *connector, int min, int
> +				   max);
>  
>  
>  /* intel_overlay.c */
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index a1799b5c12bb..82739f342246 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -2097,11 +2097,22 @@ static const struct drm_encoder_funcs intel_hdmi_enc_funcs = {
>  static void
>  intel_hdmi_add_properties(struct intel_hdmi *intel_hdmi, struct drm_connector *connector)
>  {
> +	struct drm_i915_private *dev_priv = to_i915(connector->dev);
> +
>  	intel_attach_force_audio_property(connector);
>  	intel_attach_broadcast_rgb_property(connector);
>  	intel_attach_aspect_ratio_property(connector);
>  	drm_connector_attach_content_type_property(connector);
>  	connector->state->picture_aspect_ratio = HDMI_PICTURE_ASPECT_NONE;
> +
> +	if (IS_G4X(dev_priv) || IS_VALLEYVIEW(dev_priv) ||
> +	    IS_CHERRYVIEW(dev_priv)) {
> +		intel_attach_max_bpc_property(connector, 8, 10);
> +		connector->state->max_bpc = 10;

These platforms don't support HDMI deep color. The 10bpc stuff in
PIPECONF is for DP. Incidentally DP support seems to be missing from
this series.

> +	} else if (INTEL_GEN(dev_priv) >= 5) {
> +		intel_attach_max_bpc_property(connector, 8, 12);
> +		connector->state->max_bpc = 12;
> +	}
>  }
>  
>  /*
> diff --git a/drivers/gpu/drm/i915/intel_modes.c b/drivers/gpu/drm/i915/intel_modes.c
> index ca44bf368e24..78f2ce92f194 100644
> --- a/drivers/gpu/drm/i915/intel_modes.c
> +++ b/drivers/gpu/drm/i915/intel_modes.c
> @@ -133,3 +133,23 @@ intel_attach_aspect_ratio_property(struct drm_connector *connector)
>  			connector->dev->mode_config.aspect_ratio_property,
>  			DRM_MODE_PICTURE_ASPECT_NONE);
>  }
> +
> +void
> +intel_attach_max_bpc_property(struct drm_connector *connector, int min, int
> +			       max)
> +{
> +	struct drm_device *dev = connector->dev;
> +	struct drm_mode_config *config = &dev->mode_config;
> +	struct drm_property *prop;
> +
> +	prop = config->max_bpc_property;
> +	if (prop == NULL) {
> +		prop = drm_property_create_range(dev, 0, "max bpc", min, max);
> +		if (prop == NULL)
> +			return;
> +
> +		config->max_bpc_property = prop;
> +	}
> +
> +	drm_object_attach_property(&connector->base, prop, max);

Might make sense to do 'connector->state->max_bpc = max' here.
Avoids having to sprinkle it in every driver.

> +}
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index 97ea41dc678f..d59b9e34ae80 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 being scanned out.

The comment is misleading. It makes me think this has something to do
with the pixels we scan out from a framebuffer.

> +	 */
> +	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.
>  	 */
> -- 
> 2.9.3

-- 
Ville Syrjälä
Intel
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