[Intel-gfx] [PATCH v3 23/25] drm/i915/dp_mst: Allow DSC only for sink ports of the first branch device

[Lisovskiy, Stanislav]

On Thu, Sep 14, 2023 at 10:26:57PM +0300, Imre Deak wrote:
> Atm the driver supports DSC on MST links only by enabling it globally in
> the first branch device UFP's physical DPCD (vs. enabling it per-stream
> in the virtual DPCD right upstream the DPRX). This means the branch
> device will decompress any compressed stream (which it recognizes via
> MSA / SDP compression info), but it does this only for streams going to
> an SST output port. Accordingly allow DSC only for streams going to an
> SST output port of the first branch device.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>

Reviewed-by: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_dp_mst.c | 26 +++++++++++++++++++++
>  1 file changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index b2ac29a157fbd..f24f656d6d02a 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -335,6 +335,27 @@ intel_dp_mst_compute_config_limits(struct intel_dp *intel_dp,
>  						       limits);
>  }
>  
> +static bool intel_dp_mst_port_supports_dsc(struct intel_dp *intel_dp,
> +					   struct intel_crtc_state *crtc_state,
> +					   struct drm_connector_state *conn_state)
> +{
> +	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> +	struct intel_connector *connector =
> +		to_intel_connector(conn_state->connector);
> +	struct intel_crtc *crtc =
> +		to_intel_crtc(crtc_state->uapi.crtc);
> +
> +	if (connector->port->parent != intel_dp->mst_mgr.mst_primary) {
> +		drm_dbg_kms(&i915->drm,
> +			    "[CRTC:%d:%s] DSC only allowed on sink ports of the first branch device\n",
> +			    crtc->base.base.id, crtc->base.name);
> +
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  				       struct intel_crtc_state *pipe_config,
>  				       struct drm_connector_state *conn_state)
> @@ -378,6 +399,11 @@ static int intel_dp_mst_compute_config(struct intel_encoder *encoder,
>  			    str_yes_no(ret),
>  			    str_yes_no(intel_dp->force_dsc_en));
>  
> +		if (!intel_dp_mst_port_supports_dsc(intel_dp,
> +						    pipe_config,
> +						    conn_state))
> +			return -EINVAL;
> +
>  		if (!intel_dp_mst_compute_config_limits(intel_dp,
>  							pipe_config,
>  							true,
> -- 
> 2.37.2
>