Re: [PATCH v6 13/28] drm/i915/dp: Compute DSC pipe config in atomic check

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

On Mon, Oct 29, 2018 at 10:30:39PM +0200, Ville Syrjälä wrote:
> On Wed, Oct 24, 2018 at 03:28:25PM -0700, Manasi Navare wrote:
> > DSC params like the enable, compressed bpp, slice count and
> > dsc_split are added to the intel_crtc_state. These parameters
> > are set based on the requested mode and available link parameters
> > during the pipe configuration in atomic check phase.
> > These values are then later used to populate the remaining DSC
> > and RC parameters before enbaling DSC in atomic commit.
> > 
> > v9:
> > * Rebase on top of drm-tip that now uses fast_narrow config
> > for edp (Manasi)
> > v8:
> > * Check for DSC bpc not 0 (manasi)
> > 
> > v7:
> > * Fix indentation in compute_m_n (Manasi)
> > 
> > v6 (From Gaurav):
> > * Remove function call of intel_dp_compute_dsc_params() and
> > invoke intel_dp_compute_dsc_params() in the patch where
> > it is defined to fix compilation warning (Gaurav)
> > 
> > v5:
> > Add drm_dsc_cfg in intel_crtc_state (Manasi)
> > 
> > v4:
> > * Rebase on refactoring of intel_dp_compute_config on tip (Manasi)
> > * Add a comment why we need to check PSR while enabling DSC (Gaurav)
> > 
> > v3:
> > * Check PPR > max_cdclock to use 2 VDSC instances (Ville)
> > 
> > v2:
> > * Add if-else for eDP/DP (Gaurav)
> > 
> > Cc: Jani Nikula <jani.nikula@linux.intel.com>
> > Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> > Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
> > Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> > Reviewed-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> > Acked-by: Jani Nikula <jani.nikula@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c |  20 +++-
> >  drivers/gpu/drm/i915/intel_display.h |   3 +-
> >  drivers/gpu/drm/i915/intel_dp.c      | 170 ++++++++++++++++++++++-----
> >  drivers/gpu/drm/i915/intel_dp_mst.c  |   2 +-
> >  4 files changed, 155 insertions(+), 40 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index fe045abb6472..18737bd82b68 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -6434,7 +6434,7 @@ static int ironlake_fdi_compute_config(struct intel_crtc *intel_crtc,
> >  
> >  	pipe_config->fdi_lanes = lane;
> >  
> > -	intel_link_compute_m_n(pipe_config->pipe_bpp, lane, fdi_dotclock,
> > +	intel_link_compute_m_n(pipe_config->pipe_bpp, 0, lane, fdi_dotclock,
> >  			       link_bw, &pipe_config->fdi_m_n, false);
> >  
> >  	ret = ironlake_check_fdi_lanes(dev, intel_crtc->pipe, pipe_config);
> > @@ -6671,17 +6671,25 @@ static void compute_m_n(unsigned int m, unsigned int n,
> >  }
> >  
> >  void
> > -intel_link_compute_m_n(int bits_per_pixel, int nlanes,
> > +intel_link_compute_m_n(int bits_per_pixel, uint16_t compressed_bpp,
> > +		       int nlanes,
> >  		       int pixel_clock, int link_clock,
> >  		       struct intel_link_m_n *m_n,
> >  		       bool constant_n)
> >  {
> >  	m_n->tu = 64;
> >  
> > -	compute_m_n(bits_per_pixel * pixel_clock,
> > -		    link_clock * nlanes * 8,
> > -		    &m_n->gmch_m, &m_n->gmch_n,
> > -		    constant_n);
> > +	/* For DSC, Data M/N calculation uses compressed BPP */
> > +	if (compressed_bpp)
> > +		compute_m_n(compressed_bpp * pixel_clock,
> > +			    link_clock * nlanes * 8,
> > +			    &m_n->gmch_m, &m_n->gmch_n,
> > +			    constant_n);
> > +	else
> > +		compute_m_n(bits_per_pixel * pixel_clock,
> > +			    link_clock * nlanes * 8,
> > +			    &m_n->gmch_m, &m_n->gmch_n,
> > +			    constant_n);
> >  
> >  	compute_m_n(pixel_clock, link_clock,
> >  		    &m_n->link_m, &m_n->link_n,
> > diff --git a/drivers/gpu/drm/i915/intel_display.h b/drivers/gpu/drm/i915/intel_display.h
> > index 5d50decbcbb5..b0b23e1e9392 100644
> > --- a/drivers/gpu/drm/i915/intel_display.h
> > +++ b/drivers/gpu/drm/i915/intel_display.h
> > @@ -407,7 +407,8 @@ struct intel_link_m_n {
> >  	     (__i)++) \
> >  		for_each_if(plane)
> >  
> > -void intel_link_compute_m_n(int bpp, int nlanes,
> > +void intel_link_compute_m_n(int bpp, uint16_t compressed_bpp,
> > +			    int nlanes,
> >  			    int pixel_clock, int link_clock,
> >  			    struct intel_link_m_n *m_n,
> >  			    bool constant_n);
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 6f66a38ba0b2..a88f9371dd32 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -47,6 +47,8 @@
> >  
> >  /* DP DSC small joiner has 2 FIFOs each of 640 x 6 bytes */
> >  #define DP_DSC_MAX_SMALL_JOINER_RAM_BUFFER	61440
> > +#define DP_DSC_MIN_SUPPORTED_BPC		8
> > +#define DP_DSC_MAX_SUPPORTED_BPC		10
> >  
> >  /* DP DSC throughput values used for slice count calculations KPixels/s */
> >  #define DP_DSC_PEAK_PIXEL_RATE			2720000
> > @@ -1924,6 +1926,16 @@ static int intel_dp_compute_bpp(struct intel_dp *intel_dp,
> >  		}
> >  	}
> >  
> > +	/* If DSC is supported, use the max value reported by panel */
> > +	if (INTEL_GEN(dev_priv) >= 10 &&
> > +	    drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd)) {
> > +		bpc = min_t(u8,
> > +			    drm_dp_dsc_sink_max_color_depth(intel_dp->dsc_dpcd),
> > +			    DP_DSC_MAX_SUPPORTED_BPC);
> > +		if (bpc)
> > +			bpp = 3 * bpc;
> 
> This seems like it should be 'bpp = min(bpp, 3*bpc)'. 
> Otherwise we may bump the bpp above a limit we already established earlier.
> 
> > +	}
> > +
> >  	return bpp;
> >  }
> >  
> > @@ -1984,14 +1996,11 @@ intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
> >  				link_clock = intel_dp->common_rates[clock];
> >  				link_avail = intel_dp_max_data_rate(link_clock,
> >  								    lane_count);
> > -
> > -				if (mode_rate <= link_avail) {
> > -					pipe_config->lane_count = lane_count;
> > -					pipe_config->pipe_bpp = bpp;
> > -					pipe_config->port_clock = link_clock;
> > -
> > +				pipe_config->lane_count = lane_count;
> > +				pipe_config->pipe_bpp = bpp;
> > +				pipe_config->port_clock = link_clock;
> > +				if (mode_rate <= link_avail)
> >  					return true;
> 
> Why do we need to assign these if we don't accept the configuration?
> 
> > -				}
> >  			}
> >  		}
> >  	}
> > @@ -2020,14 +2029,11 @@ intel_dp_compute_link_config_fast(struct intel_dp *intel_dp,
> >  				link_clock = intel_dp->common_rates[clock];
> >  				link_avail = intel_dp_max_data_rate(link_clock,
> >  								    lane_count);
> > -
> > -				if (mode_rate <= link_avail) {
> > -					pipe_config->lane_count = lane_count;
> > -					pipe_config->pipe_bpp = bpp;
> > -					pipe_config->port_clock = link_clock;
> > -
> > +				pipe_config->lane_count = lane_count;
> > +				pipe_config->pipe_bpp = bpp;
> > +				pipe_config->port_clock = link_clock;
> > +				if (mode_rate <= link_avail)
> >  					return true;
> > -				}
> >  			}
> >  		}
> >  	}
> > @@ -2035,14 +2041,88 @@ intel_dp_compute_link_config_fast(struct intel_dp *intel_dp,
> >  	return false;
> >  }
> >  
> > +static bool intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> > +					struct intel_crtc_state *pipe_config,
> > +					struct link_config_limits *limits)
> > +{
> > +	struct intel_digital_port *dig_port = dp_to_dig_port(intel_dp);
> > +	struct drm_i915_private *dev_priv = to_i915(dig_port->base.base.dev);
> > +	struct drm_display_mode *adjusted_mode = &pipe_config->base.adjusted_mode;
> > +	enum pipe pipe = to_intel_crtc(pipe_config->base.crtc)->pipe;
> > +	u16 dsc_max_output_bpp = 0;
> > +	u8 dsc_dp_slice_count = 0;
> > +
> > +	if (INTEL_GEN(dev_priv) < 10 ||
> > +	    !drm_dp_sink_supports_dsc(intel_dp->dsc_dpcd))
> > +		return false;
> > +
> > +	/* DP DSC only supported on Pipe B and C */
> > +	if (pipe == PIPE_A && !intel_dp_is_edp(intel_dp))
> > +		return false;
> 
> Do we mean 'transcoder == EDP || transcoder == B || transcoder == C' ?
> Or maybe 'transcoder != A' for short. I guess this will need to adjusted
> for the next platform anyway so making the assumption that transcoder A
> is the only one that can't do DSC is fine.
> 
> This whole thing seems like a good helper function.
> intel_dp_source_supports_dsc() or something like that. And then we
> could have intel_dp_supports_dsc() which just calls that +
> drm_dp_sink_supports_dsc().

Another confusion about these checks is glk. Some other places seem
to indicate that glk has DSC, but then code like this here doesn't 
accept glk. What's up with that?

-- 
Ville Syrjälä
Intel
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