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

["Lisovskiy, Stanislav" <stanislav.lisovskiy@intel.com>]

On Fri, Oct 27, 2023 at 05:53:17PM +0300, Imre Deak wrote:
> On Fri, Oct 27, 2023 at 05:45:30PM +0300, Lisovskiy, Stanislav wrote:
> > 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@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.
> 
> use_count is recalculated for the current state, based on
> each connector's dsc_decompression_enabled flag and whether the
> given connector's AUX device matches what this function wants to use to
> enable/disable the decompression. So use_count will be the number of
> connectors at the moment which have decompression enabled through the
> AUX device in question.
> 
> > For that we need to have intel_connector->dp.dsc_decompression_aux NULLed somewhere?
> 
> No, it stays set, but dsc_decompression_enabled does get set/cleared.

Got it,

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

> 
> > 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
> > >