Re: [PATCH RFC v2 05/37] drm/connector: hdmi: Add output BPC to the connector state

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Wed, 20 Sep 2023 16:35:20 +0200
Maxime Ripard <mripard@kernel.org> wrote:

> We'll add automatic selection of the output BPC in a following patch,
> but let's add it to the HDMI connector state already.
> 
> Signed-off-by: Maxime Ripard <mripard@kernel.org>
> ---
>  drivers/gpu/drm/drm_atomic.c              |  4 +++-
>  drivers/gpu/drm/drm_atomic_state_helper.c |  6 +++++-
>  drivers/gpu/drm/drm_connector.c           | 13 ++++++++++++-
>  include/drm/drm_connector.h               | 13 ++++++++++++-
>  4 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index b1b56dcaa76b..8dce0a2f2ac3 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1143,9 +1143,11 @@ static void drm_atomic_connector_print_state(struct drm_printer *p,
>  	drm_printf(p, "\tcolorspace=%s\n", drm_get_colorspace_name(state->colorspace));
>  
>  	if (connector->connector_type == DRM_MODE_CONNECTOR_HDMIA ||
> -	    connector->connector_type == DRM_MODE_CONNECTOR_HDMIB)
> +	    connector->connector_type == DRM_MODE_CONNECTOR_HDMIB) {
>  		drm_printf(p, "\tbroadcast_rgb=%s\n",
>  			   drm_hdmi_connector_get_broadcast_rgb_name(state->hdmi.broadcast_rgb));
> +		drm_printf(p, "\toutput_bpc=%u\n", state->hdmi.output_bpc);
> +	}
>  
>  	if (connector->connector_type == DRM_MODE_CONNECTOR_WRITEBACK)
>  		if (state->writeback_job && state->writeback_job->fb)
> diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c b/drivers/gpu/drm/drm_atomic_state_helper.c
> index 0f7e5ba555b8..2c9b52ae1b56 100644
> --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> @@ -569,6 +569,9 @@ EXPORT_SYMBOL(drm_atomic_helper_connector_tv_reset);
>  void __drm_atomic_helper_connector_hdmi_reset(struct drm_connector *connector,
>  					      struct drm_connector_state *new_state)
>  {
> +	new_state->max_bpc = 8;
> +	new_state->max_requested_bpc = 8;
> +	new_state->hdmi.output_bpc = 8;

Hi,

will this be forcing all drivers using these helpers to default to max bpc = 8?

I believe at least amdgpu would disagree. The defaults were changed in
the recent years, IIRC to avoid extra modesets during boot-up when
desktops prefer highest possible bpc for a mode.

The 'max bpc' property itself is a manual workaround for faulty
hardware that does not correctly indicate the max bpc it can handle. It
should not default to be a limiting factor.

>  	new_state->hdmi.broadcast_rgb = DRM_HDMI_BROADCAST_RGB_AUTO;
>  }
>  EXPORT_SYMBOL(__drm_atomic_helper_connector_hdmi_reset);
> @@ -651,7 +654,8 @@ int drm_atomic_helper_connector_hdmi_check(struct drm_connector *connector,
>  	struct drm_connector_state *new_state =
>  		drm_atomic_get_new_connector_state(state, connector);
>  
> -	if (old_state->hdmi.broadcast_rgb != new_state->hdmi.broadcast_rgb) {
> +	if (old_state->hdmi.broadcast_rgb != new_state->hdmi.broadcast_rgb ||
> +	    old_state->hdmi.output_bpc != new_state->hdmi.output_bpc) {
>  		struct drm_crtc *crtc = new_state->crtc;
>  		struct drm_crtc_state *crtc_state;
>  
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index b45471d540ac..f55f5918411c 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -459,6 +459,7 @@ EXPORT_SYMBOL(drmm_connector_init);
>   * @funcs: callbacks for this connector
>   * @connector_type: user visible type of the connector
>   * @ddc: optional pointer to the associated ddc adapter
> + * @max_bpc: Maximum bits per char the HDMI connector supports
>   *
>   * Initialises a preallocated HDMI connector. Connectors can be
>   * subclassed as part of driver connector objects.
> @@ -475,7 +476,8 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
>  			     struct drm_connector *connector,
>  			     const struct drm_connector_funcs *funcs,
>  			     int connector_type,
> -			     struct i2c_adapter *ddc)
> +			     struct i2c_adapter *ddc,
> +			     unsigned int max_bpc)
>  {
>  	int ret;
>  
> @@ -487,6 +489,15 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
>  	if (ret)
>  		return ret;
>  
> +	if (max_bpc) {
> +		if (!(max_bpc == 8 || max_bpc == 10 || max_bpc == 12))
> +			return -EINVAL;
> +
> +		drm_connector_attach_hdr_output_metadata_property(connector);
> +		drm_connector_attach_max_bpc_property(connector, 8, max_bpc);
> +		connector->max_bpc = max_bpc;
> +	}
> +
>  	return 0;
>  }
>  EXPORT_SYMBOL(drmm_connector_hdmi_init);
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index fdcf64ab91a9..d0bcb835c857 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1056,6 +1056,11 @@ struct drm_connector_state {
>  		 * Broadcast RGB selection value.
>  		 */
>  		enum drm_hdmi_broadcast_rgb broadcast_rgb;
> +
> +		/**
> +		 * @output_bpc: Bits per character to output.

Is it not bits per channel?

> +		 */
> +		unsigned int output_bpc;
>  	} hdmi;
>  };
>  
> @@ -1700,6 +1705,11 @@ struct drm_connector {
>  	 */
>  	struct drm_property_blob *path_blob_ptr;
>  
> +	/**
> +	 * @max_bpc: Maximum bits per character the connector supports.

channel?

> +	 */
> +	unsigned int max_bpc;
> +
>  	/**
>  	 * @max_bpc_property: Default connector property for the max bpc to be
>  	 * driven out of the connector.
> @@ -1939,7 +1949,8 @@ int drmm_connector_hdmi_init(struct drm_device *dev,
>  			     struct drm_connector *connector,
>  			     const struct drm_connector_funcs *funcs,
>  			     int connector_type,
> -			     struct i2c_adapter *ddc);
> +			     struct i2c_adapter *ddc,
> +			     unsigned int max_bpc);
>  void drm_connector_attach_edid_property(struct drm_connector *connector);
>  int drm_connector_register(struct drm_connector *connector);
>  void drm_connector_unregister(struct drm_connector *connector);
> 

Thanks,
pq

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