[Intel-gfx] [PATCH 23/29] drm/i915/dp_mst: Enable DSC passthrough

[Ville Syrjälä]

On Tue, Oct 24, 2023 at 04:09:19AM +0300, Imre Deak wrote:
> Enable passing through DSC streams to the sink in last branch devices.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp.c | 26 ++++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index a7eb31b489947..bb8951f89f61f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -2950,6 +2950,24 @@ intel_dp_sink_set_dsc_decompression(struct intel_connector *connector,
>  			    str_enable_disable(enable));
>  }
>  
> +static void
> +intel_dp_sink_set_dsc_passthrough(const struct intel_connector *connector,
> +				  bool enable)
> +{
> +	struct drm_i915_private *i915 = to_i915(connector->base.dev);
> +	struct drm_dp_aux *aux = connector->port ?
> +				 connector->port->passthrough_aux : NULL;

I was worried that we're now setting conflicting compress+passthrough
bits at the same time, but looks like this magic passthrough_aux thing
gets sneakily populated by drm_dp_mst_dsc_aux_for_port() whereas the 
decompression_aux gets just returned directly and tracked by the driver.
Very confusing.

But I guess it kinda works
Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> +
> +	if (!aux)
> +		return;
> +
> +	if (drm_dp_dpcd_writeb(aux, DP_DSC_PASSTHROUGH_EN,
> +			       enable ? DP_DSC_PASSTHROUGH_EN : 0) < 0)
> +		drm_dbg_kms(&i915->drm,
> +			    "Failed to %s sink compression passthrough state\n",
> +			    str_enable_disable(enable));
> +}
> +
>  void intel_dp_sink_set_decompression_state(struct intel_connector *connector,
>  					   const struct intel_crtc_state *crtc_state,
>  					   bool enable)
> @@ -2962,7 +2980,13 @@ void intel_dp_sink_set_decompression_state(struct intel_connector *connector,
>  	if (drm_WARN_ON(&i915->drm, !connector->dp.dsc_decompression_aux))
>  		return;
>  
> -	intel_dp_sink_set_dsc_decompression(connector, enable);
> +	if (enable) {
> +		intel_dp_sink_set_dsc_passthrough(connector, true);
> +		intel_dp_sink_set_dsc_decompression(connector, true);
> +	} else {
> +		intel_dp_sink_set_dsc_decompression(connector, false);
> +		intel_dp_sink_set_dsc_passthrough(connector, false);
> +	}
>  }
>  
>  static void
> -- 
> 2.39.2

-- 
Ville Syrjälä
Intel