[Intel-gfx] [PATCH 24/29] drm/i915/dp_mst: Enable MST DSC decompression for all streams

[Lisovskiy, Stanislav]

On Tue, Oct 24, 2023 at 04:09:20AM +0300, Imre Deak wrote:
> Enable DSC decompression for all streams. In particular atm if a sink is
> connected to a last branch device that is downstream of the first branch
> device connected to the source, decompression is not enabled for it.
> Similarly it's not enabled if the sink supports this with the last
> branch device passing through the compressed stream to it.
> 
> Enable DSC in the above cases as well. Since last branch devices may
> handle the decompression for multiple ports, toggling DSC needs to be
> refcounted, add this using the DSC AUX device as a reference.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> ---
>  .../drm/i915/display/intel_display_types.h    |  1 +
>  drivers/gpu/drm/i915/display/intel_dp.c       |  3 +
>  drivers/gpu/drm/i915/display/intel_dp_mst.c   | 57 ++++++++++++-------
>  3 files changed, 42 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_types.h b/drivers/gpu/drm/i915/display/intel_display_types.h
> index 409dbf8a2a1cd..b2744a9b4678c 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_types.h
> +++ b/drivers/gpu/drm/i915/display/intel_display_types.h
> @@ -626,6 +626,7 @@ struct intel_connector {
>  		u8 fec_capability;
>  
>  		u8 dsc_hblank_expansion_quirk:1;
> +		u8 dsc_decompression_enabled:1;
>  	} dp;
>  
>  	/* Work struct to schedule a uevent on link train failure */
> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> index bb8951f89f61f..c89e1a4393d0f 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -1403,6 +1403,7 @@ static bool intel_dp_supports_dsc(const struct intel_connector *connector,
>  		return false;
>  
>  	return intel_dsc_source_support(crtc_state) &&
> +		connector->dp.dsc_decompression_aux &&
>  		drm_dp_sink_supports_dsc(connector->dp.dsc_dpcd);
>  }
>  
> @@ -2948,6 +2949,8 @@ intel_dp_sink_set_dsc_decompression(struct intel_connector *connector,
>  		drm_dbg_kms(&i915->drm,
>  			    "Failed to %s sink decompression state\n",
>  			    str_enable_disable(enable));
> +
> +	connector->dp.dsc_decompression_enabled = enable;
>  }
>  
>  static void
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> index 8ef3a2611207c..9f4894c2e7860 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> @@ -660,6 +660,39 @@ intel_dp_mst_atomic_topology_check(struct intel_connector *connector,
>  	return ret;
>  }
>  
> +static int intel_dp_mst_dsc_aux_use_count(struct intel_atomic_state *state,
> +					  const struct intel_connector *connector)
> +{
> +	struct intel_connector *connector_iter;
> +	struct intel_digital_connector_state *conn_state;
> +	int use_count = 0;
> +	int i;
> +
> +	for_each_new_intel_connector_in_state(state, connector_iter, conn_state, i) {
> +		if (connector_iter->mst_port != connector->mst_port ||
> +		    !conn_state->base.crtc)
> +			continue;
> +
> +		if (!connector_iter->dp.dsc_decompression_enabled)
> +			continue;
> +
> +		if (connector_iter->dp.dsc_decompression_aux ==
> +		    connector->dp.dsc_decompression_aux)
> +			use_count++;
> +	}
> +
> +	return use_count;
> +}
> +
> +static void intel_dp_mst_sink_set_decompression_state(struct intel_atomic_state *state,
> +						      struct intel_connector *connector,
> +						      const struct intel_crtc_state *crtc_state,
> +						      bool enable)
> +{
> +	if (!intel_dp_mst_dsc_aux_use_count(state, connector))
> +		intel_dp_sink_set_decompression_state(connector, crtc_state, enable);

But where the use count is decremented?
As I understand we will be able to set this with enable==false also when use_count is 0.

For that we need to have intel_connector->dp.dsc_decompression_aux NULLed somewhere?

Stan
> +}
> +
>  static int
>  intel_dp_mst_atomic_check(struct drm_connector *connector,
>  			  struct drm_atomic_state *_state)
> @@ -730,12 +763,7 @@ static void intel_mst_disable_dp(struct intel_atomic_state *state,
>  
>  	intel_audio_codec_disable(encoder, old_crtc_state, old_conn_state);
>  
> -	if (intel_dp->active_mst_links == 1) /* last stream ? */
> -		/*
> -		 * TODO: disable decompression for all streams/in any MST ports, not
> -		 * only in the first downstream branch device.
> -		 */
> -		intel_dp_sink_set_decompression_state(connector, old_crtc_state, false);
> +	intel_dp_mst_sink_set_decompression_state(state, connector, old_crtc_state, false);
>  }
>  
>  static void intel_mst_post_disable_dp(struct intel_atomic_state *state,
> @@ -890,15 +918,11 @@ static void intel_mst_pre_enable_dp(struct intel_atomic_state *state,
>  
>  	drm_dp_send_power_updown_phy(&intel_dp->mst_mgr, connector->port, true);
>  
> -	if (first_mst_stream) {
> -		/*
> -		 * TODO: enable decompression for all streams/in any MST ports, not
> -		 * only in the first downstream branch device.
> -		 */
> -		intel_dp_sink_set_decompression_state(connector, pipe_config, true);
> +	intel_dp_mst_sink_set_decompression_state(state, connector, pipe_config, true);
> +
> +	if (first_mst_stream)
>  		dig_port->base.pre_enable(state, &dig_port->base,
>  						pipe_config, NULL);
> -	}
>  
>  	intel_dp->active_mst_links++;
>  
> @@ -1350,12 +1374,7 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
>  
>  	drm_connector_helper_add(connector, &intel_dp_mst_connector_helper_funcs);
>  
> -	/*
> -	 * TODO: set the AUX for the actual MST port decompressing the stream.
> -	 * At the moment the driver only supports enabling this globally in the
> -	 * first downstream MST branch, via intel_dp's (root port) AUX.
> -	 */
> -	intel_connector->dp.dsc_decompression_aux = &intel_dp->aux;
> +	intel_connector->dp.dsc_decompression_aux = drm_dp_mst_dsc_aux_for_port(port);
>  	intel_dp_mst_read_decompression_port_dsc_caps(intel_dp, intel_connector);
>  	intel_connector->dp.dsc_hblank_expansion_quirk =
>  		detect_dsc_hblank_expansion_quirk(intel_connector);
> -- 
> 2.39.2
>