Re: [Intel-gfx] [PATCH 05/11] drm/i915: Check lane count when determining FEC support

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, May 25, 2023 at 11:09:30AM +0300, Luca Coelho wrote:
> On Tue, 2023-05-02 at 17:39 +0300, Ville Syrjala wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > ICL doesn't support FEC with a x1 DP link. Make sure
> > we don't try to enable FEC in such cases.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 23 ++++++++++++-----------
> >  1 file changed, 12 insertions(+), 11 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index b27b4fb71ed7..9ac199444155 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1218,7 +1218,8 @@ static bool intel_dp_source_supports_fec(struct intel_dp *intel_dp,
> >  	if (DISPLAY_VER(dev_priv) >= 12)
> >  		return true;
> >  
> > -	if (DISPLAY_VER(dev_priv) == 11 && encoder->port != PORT_A)
> > +	if (DISPLAY_VER(dev_priv) == 11 &&
> > +	    encoder->port != PORT_A && pipe_config->lane_count != 1)
> >  		return true;
> >  
> >  	return false;
> > @@ -1234,7 +1235,7 @@ static bool intel_dp_supports_fec(struct intel_dp *intel_dp,
> >  static bool intel_dp_supports_dsc(struct intel_dp *intel_dp,
> >  				  const struct intel_crtc_state *crtc_state)
> >  {
> > -	if (intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP) && !crtc_state->fec_enable)
> > +	if (!intel_dp_is_edp(intel_dp) && !crtc_state->fec_enable)
> 
> I'm probably missing something, but this change...

This should have been a separate change I suppose. What this is
currently asserting is DP-SST needs FEC to use DSC, but so does DP-MST
which this is totally forgetting to check. eDP is only case where we
can skip FEC.

> 
> 
> >  		return false;
> >  
> >  	return intel_dsc_source_support(crtc_state) &&
> > @@ -1580,15 +1581,6 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> >  	int pipe_bpp;
> >  	int ret;
> >  
> > -	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
> > -		intel_dp_supports_fec(intel_dp, pipe_config);
> > -
> > -	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
> > -		return -EINVAL;
> > -
> > -	if (!intel_dp_dsc_supports_format(intel_dp, pipe_config->output_format))
> > -		return -EINVAL;
> > -
> >  	if (compute_pipe_bpp)
> >  		pipe_bpp = intel_dp_dsc_compute_bpp(intel_dp, conn_state->max_requested_bpc);
> >  	else
> > @@ -1615,6 +1607,15 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> >  	pipe_config->port_clock = limits->max_rate;
> >  	pipe_config->lane_count = limits->max_lane_count;
> >  
> > +	pipe_config->fec_enable = !intel_dp_is_edp(intel_dp) &&
> > +		intel_dp_supports_fec(intel_dp, pipe_config);
> > +
> > +	if (!intel_dp_supports_dsc(intel_dp, pipe_config))
> > +		return -EINVAL;
> > +
> > +	if (!intel_dp_dsc_supports_format(intel_dp, pipe_config->output_format))
> > +		return -EINVAL;
> > +
> >  	if (intel_dp_is_edp(intel_dp)) {
> >  		pipe_config->dsc.compressed_bpp =
> >  			min_t(u16, drm_edp_dsc_sink_output_bpp(intel_dp->dsc_dpcd) >> 4,
> 
> ...and this code move are not explained in the commit message? How are
> they related?

This is moved becaue we need to compute lanel_count before we can
actually check it.

-- 
Ville Syrjälä
Intel