Re: [PATCH 10/20] drm/i915/dp: Add functions to get min/max src input bpc with DSC

["Nautiyal, Ankit K" <ankit.k.nautiyal@xxxxxxxxx>]

On 8/2/2023 5:35 PM, Lisovskiy, Stanislav wrote:
> On Fri, Jul 28, 2023 at 09:41:40AM +0530, Ankit Nautiyal wrote:
> > Separate out functions for getting maximum and minimum input BPC based
> > on platforms, when DSC is used.
> >
> > Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/display/intel_dp.c | 38 +++++++++++++++++++------
> >   1 file changed, 30 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 7ec8a478e000..f41de126a8d3 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1535,6 +1535,18 @@ intel_dp_compute_link_config_wide(struct intel_dp *intel_dp,
> >   	return -EINVAL;
> >   }
> >   
> > +static
> > +u8 intel_dp_dsc_max_src_input_bpc(struct drm_i915_private *i915)
> > +{
> > +	/* Max DSC Input BPC for ICL is 10 and for TGL+ is 12 */
> > +	if (DISPLAY_VER(i915) >= 12)
> > +		return 12;
> > +	if (DISPLAY_VER(i915) == 11)
> > +		return 10;
> > +
> > +	return 0;
> > +}
> > +
> >   int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 max_req_bpc)
> >   {
> >   	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > @@ -1542,11 +1554,12 @@ int intel_dp_dsc_compute_bpp(struct intel_dp *intel_dp, u8 max_req_bpc)
> >   	u8 dsc_bpc[3] = {0};
> >   	u8 dsc_max_bpc;
> >   
> > -	/* Max DSC Input BPC for ICL is 10 and for TGL+ is 12 */
> > -	if (DISPLAY_VER(i915) >= 12)
> > -		dsc_max_bpc = min_t(u8, 12, max_req_bpc);
> > -	else
> > -		dsc_max_bpc = min_t(u8, 10, max_req_bpc);
> > +	dsc_max_bpc = intel_dp_dsc_max_src_input_bpc(i915);
> > +
> > +	if (!dsc_max_bpc)
> > +		return dsc_max_bpc;
> > +
> > +	dsc_max_bpc = min_t(u8, dsc_max_bpc, max_req_bpc);
> >   
> >   	num_bpc = drm_dp_dsc_sink_supported_input_bpcs(intel_dp->dsc_dpcd,
> >   						       dsc_bpc);
> > @@ -1674,6 +1687,16 @@ static bool intel_dp_dsc_supports_format(struct intel_dp *intel_dp,
> >   	return drm_dp_dsc_sink_supports_format(intel_dp->dsc_dpcd, sink_dsc_format);
> >   }
> >   
> > +static
> > +u8 intel_dp_dsc_min_src_input_bpc(struct drm_i915_private *i915)
> > +{
> > +	/* Min DSC Input BPC for ICL+ is 8 */
> > +	if (DISPLAY_VER(i915) >= 11)
> > +		return 8;
> > +
> > +	return 0;
> So does it mean that for anything below gen 11, there is no limit at all?
> Also it means that the condition below will never be executed for gen <= 11.

Hmm. Bspec says min bpc is 8 for DSC, so idea is to have min bpc as 8 
when DSC is used.

This is supposed to be called only if DSC is supported, so perhaps 
HAS_DSC can be used?

return HAS_DSC(dev_priv) ? 8 : 0;


Regards,

Ankit

> Stan
>
> > +}
> > +
> >   int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> >   				struct intel_crtc_state *pipe_config,
> >   				struct drm_connector_state *conn_state,
> > @@ -1707,10 +1730,9 @@ int intel_dp_dsc_compute_config(struct intel_dp *intel_dp,
> >   		pipe_bpp = pipe_config->pipe_bpp;
> >   	}
> >   
> > -	/* Min Input BPC for ICL+ is 8 */
> > -	if (pipe_bpp < 8 * 3) {
> > +	if (pipe_bpp < intel_dp_dsc_min_src_input_bpc(dev_priv) * 3) {
> >   		drm_dbg_kms(&dev_priv->drm,
> > -			    "No DSC support for less than 8bpc\n");
> > +			    "Computed BPC less than min supported by source for DSC\n");
> >   		return -EINVAL;
> >   	}
> >   
> > --
> > 2.40.1