Re: [PATCH v2 1/3] drm/display: bridge-connector: add DisplayPort bridges

[Maxime Ripard]

On Fri, Feb 14, 2025 at 02:32:56AM +0200, Dmitry Baryshkov wrote:
> On Fri, Feb 14, 2025 at 01:57:45AM +0200, Laurent Pinchart wrote:
> > Hi Dmitry,
> > 
> > Thank you for the patch.
> > 
> > On Sun, Feb 09, 2025 at 03:41:18PM +0200, Dmitry Baryshkov wrote:
> > > DRM HDMI Codec framework is useful not only for the HDMI bridges, but
> > > also for the DisplayPort bridges. Add new DRM_BRIDGE_OP_DisplayPort
> > > define in order to distinguish DP bridges. Create HDMI codec device
> > > automatically for DP bridges which have declared audio support.
> > > 
> > > Note, unlike HDMI devices, which already have a framework to handle HPD
> > > notifications in a standard way, DP drivers don't (yet?) have such a
> > > framework. As such it is necessary to manually call
> > > drm_connector_hdmi_audio_plugged_notify(). This requirement hopefully
> > > can be lifted later on, if/when DRM framework gets better DisplayPort
> > > ports support in the core layer.
> > > 
> > > Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > > ---
> > >  drivers/gpu/drm/display/drm_bridge_connector.c | 66 ++++++++++++++++++++------
> > >  include/drm/drm_bridge.h                       | 14 +++++-
> > >  2 files changed, 65 insertions(+), 15 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/display/drm_bridge_connector.c b/drivers/gpu/drm/display/drm_bridge_connector.c
> > > index 30c736fc0067e31a97db242e5b16ea8a5b4cf359..5e031395b801f9a1371dcb4ac09f3da23e4615dd 100644
> > > --- a/drivers/gpu/drm/display/drm_bridge_connector.c
> > > +++ b/drivers/gpu/drm/display/drm_bridge_connector.c
> > > @@ -98,6 +98,13 @@ struct drm_bridge_connector {
> > >  	 * HDMI connector infrastructure, if any (see &DRM_BRIDGE_OP_HDMI).
> > >  	 */
> > >  	struct drm_bridge *bridge_hdmi;
> > > +	/**
> > > +	 * @bridge_dp:
> > > +	 *
> > > +	 * The bridge in the chain that implements necessary support for the
> > > +	 * DisplayPort connector infrastructure, if any (see &DRM_BRIDGE_OP_DisplayPort).
> > > +	 */
> > > +	struct drm_bridge *bridge_dp;
> > >  };
> > >  
> > >  #define to_drm_bridge_connector(x) \
> > > @@ -496,6 +503,25 @@ static const struct drm_connector_hdmi_audio_funcs drm_bridge_connector_hdmi_aud
> > >  	.mute_stream = drm_bridge_connector_audio_mute_stream,
> > >  };
> > >  
> > > +static int drm_bridge_connector_hdmi_audio_init(struct drm_connector *connector,
> > > +						struct drm_bridge *bridge)
> > > +{
> > > +	if (!bridge->hdmi_audio_max_i2s_playback_channels &&
> > > +	    !bridge->hdmi_audio_spdif_playback)
> > > +		return 0;
> > > +
> > > +	if (!bridge->funcs->hdmi_audio_prepare ||
> > > +	    !bridge->funcs->hdmi_audio_shutdown)
> > > +		return -EINVAL;
> > > +
> > > +	return drm_connector_hdmi_audio_init(connector,
> > > +					     bridge->hdmi_audio_dev,
> > > +					     &drm_bridge_connector_hdmi_audio_funcs,
> > > +					     bridge->hdmi_audio_max_i2s_playback_channels,
> > > +					     bridge->hdmi_audio_spdif_playback,
> > > +					     bridge->hdmi_audio_dai_port);
> > > +}
> > > +
> > >  /* -----------------------------------------------------------------------------
> > >   * Bridge Connector Initialisation
> > >   */
> > > @@ -564,6 +590,8 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > >  		if (bridge->ops & DRM_BRIDGE_OP_HDMI) {
> > >  			if (bridge_connector->bridge_hdmi)
> > >  				return ERR_PTR(-EBUSY);
> > > +			if (bridge_connector->bridge_dp)
> > > +				return ERR_PTR(-EINVAL);
> > >  			if (!bridge->funcs->hdmi_write_infoframe ||
> > >  			    !bridge->funcs->hdmi_clear_infoframe)
> > >  				return ERR_PTR(-EINVAL);
> > > @@ -576,6 +604,16 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > >  				max_bpc = bridge->max_bpc;
> > >  		}
> > >  
> > > +		if (bridge->ops & DRM_BRIDGE_OP_DisplayPort) {
> > > +			if (bridge_connector->bridge_dp)
> > > +				return ERR_PTR(-EBUSY);
> > > +			if (bridge_connector->bridge_hdmi)
> > > +				return ERR_PTR(-EINVAL);
> > > +
> > > +			bridge_connector->bridge_dp = bridge;
> > > +
> > > +		}
> > > +
> > >  		if (!drm_bridge_get_next_bridge(bridge))
> > >  			connector_type = bridge->type;
> > >  
> > > @@ -612,21 +650,21 @@ struct drm_connector *drm_bridge_connector_init(struct drm_device *drm,
> > >  		if (ret)
> > >  			return ERR_PTR(ret);
> > >  
> > > -		if (bridge->hdmi_audio_max_i2s_playback_channels ||
> > > -		    bridge->hdmi_audio_spdif_playback) {
> > > -			if (!bridge->funcs->hdmi_audio_prepare ||
> > > -			    !bridge->funcs->hdmi_audio_shutdown)
> > > -				return ERR_PTR(-EINVAL);
> > > +		ret = drm_bridge_connector_hdmi_audio_init(connector, bridge);
> > > +		if (ret)
> > > +			return ERR_PTR(ret);
> > > +	} else if (bridge_connector->bridge_dp) {
> > > +		bridge = bridge_connector->bridge_dp;
> > >  
> > > -			ret = drm_connector_hdmi_audio_init(connector,
> > > -							    bridge->hdmi_audio_dev,
> > > -							    &drm_bridge_connector_hdmi_audio_funcs,
> > > -							    bridge->hdmi_audio_max_i2s_playback_channels,
> > > -							    bridge->hdmi_audio_spdif_playback,
> > > -							    bridge->hdmi_audio_dai_port);
> > > -			if (ret)
> > > -				return ERR_PTR(ret);
> > > -		}
> > > +		ret = drmm_connector_init(drm, connector,
> > > +					  &drm_bridge_connector_funcs,
> > > +					  connector_type, ddc);
> > > +		if (ret)
> > > +			return ERR_PTR(ret);
> > > +
> > > +		ret = drm_bridge_connector_hdmi_audio_init(connector, bridge);
> > > +		if (ret)
> > > +			return ERR_PTR(ret);
> > >  	} else {
> > >  		ret = drmm_connector_init(drm, connector,
> > >  					  &drm_bridge_connector_funcs,
> > > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > > index 496dbbd2ad7edff7f091adfbe62de1e33ef0cf07..40f37444426b1b8ded25da9ba9e2963f18ad6267 100644
> > > --- a/include/drm/drm_bridge.h
> > > +++ b/include/drm/drm_bridge.h
> > > @@ -811,9 +811,21 @@ enum drm_bridge_ops {
> > >  	 *
> > >  	 * Note: currently there can be at most one bridge in a chain that sets
> > >  	 * this bit. This is to simplify corresponding glue code in connector
> > > -	 * drivers.
> > > +	 * drivers. Having both HDMI and DisplayPort bridges in the same bridge
> > > +	 * chain is also not allowed.
> > >  	 */
> > >  	DRM_BRIDGE_OP_HDMI = BIT(4),
> > > +	/**
> > > +	 * @DRM_BRIDGE_OP_DisplayPort: The bridge provides DisplayPort connector
> > > +	 * operations. Currently this is limited to the optional HDMI codec
> > > +	 * support.
> > > +	 *
> > > +	 * Note: currently there can be at most one bridge in a chain that sets
> > > +	 * this bit. This is to simplify corresponding glue code in connector
> > > +	 * drivers. Having both HDMI and DisplayPort bridges in the same bridge
> > > +	 * chain is also not allowed.
> > > +	 */
> > > +	DRM_BRIDGE_OP_DisplayPort = BIT(5),
> > 
> > The OP bits are not supposed to describe tbe type of bridge, but the
> > operations it implements. I see quite a bit of duplication between HDMI
> > and DisplayPort in this patch. Can we have a single bit named after the
> > feature that you want to support ? The bridge_hdmi and bridge_dp fields
> > should also be merged into a single one.
> 
> In this case these ops actually describe the set of ops implemented by
> the bridge. DRM_BRIDGE_OP_HDMI implements hdmi_tmds_char_rate_valid(),
> hdmi_write_infoframe(), hdmi_clear_infoframe()

Those are required for HDMI bridges (using the common infrastructure).

> and hdmi_audio_*() callbacks.

But those are certainly not required.

If the OP enum is meant to list what a bridge implements, then we need
to have a different enum for video, audio, and CEC.

Maxime

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