Re: [PATCH 4/4] drm/i915/dp: Ignore max_requested_bpc if its too low for DSC

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

On 11/9/2023 12:19 PM, Kandpal, Suraj wrote:
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Ankit
> > Nautiyal
> > Sent: Tuesday, November 7, 2023 9:48 AM
> > To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > Cc: Nikula, Jani <jani.nikula@xxxxxxxxx>
> > Subject:  [PATCH 4/4] drm/i915/dp: Ignore max_requested_bpc if its
> > too low for DSC
> >
> > At the moment, while choosing the input bpc for DSC, we take into account the
> > max_requested_bpc property. This creates a problem, if the
> > max_requested_bpc is lower than the minimum bpc required by source with
> > DSC.
> >
> > So consider max_requested_bpc if its within the limits that we can support with
> > DSC.
> >
> > Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@xxxxxxxxx>
> > ---
> >   drivers/gpu/drm/i915/display/intel_dp.c | 22 ++++++++++++++++++----
> >   1 file changed, 18 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index abc718f1a878..ea4c42a5705e 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -1578,6 +1578,16 @@ u8 intel_dp_dsc_max_src_input_bpc(struct
> > drm_i915_private *i915)
> >   	return 12;
> >   }
> >
> > +static int
> > +intel_dp_dsc_limit_max_bpc(int max_requested_bpc, int src_dsc_max_bpc,
> > +int src_dsc_min_bpc) {
> > +	/* Consider max_requested_bpc only if src can support it with DSC */
> > +	if (max_requested_bpc >= src_dsc_min_bpc)
> > +		return min(src_dsc_max_bpc, max_requested_bpc);
> > +
> > +	return src_dsc_max_bpc;
> > +}
> > +
> >   int intel_dp_dsc_compute_max_bpp(const struct intel_connector *connector,
> >   				 u8 max_req_bpc)
> >   {
> > @@ -1591,7 +1601,8 @@ int intel_dp_dsc_compute_max_bpp(const struct
> > intel_connector *connector,
> >   	if (!dsc_max_bpc)
> >   		return dsc_max_bpc;
> >
> > -	dsc_max_bpc = min_t(u8, dsc_max_bpc, max_req_bpc);
> > +	dsc_max_bpc = intel_dp_dsc_limit_max_bpc(max_req_bpc,
> > dsc_max_bpc,
> > +
> > intel_dp_dsc_min_src_input_bpc(i915));
> >
> >   	num_bpc = drm_dp_dsc_sink_supported_input_bpcs(connector-
> > > dp.dsc_dpcd,
> >   						       dsc_bpc);
> > @@ -1959,8 +1970,11 @@ bool is_dsc_pipe_bpp_sufficient(struct
> > drm_i915_private *i915,  {
> >   	u8 dsc_max_bpc, dsc_min_bpc, dsc_max_pipe_bpp,
> > dsc_min_pipe_bpp;
> >
> > -	dsc_max_bpc = min(intel_dp_dsc_max_src_input_bpc(i915),
> > conn_state->max_requested_bpc);
> >   	dsc_min_bpc = intel_dp_dsc_min_src_input_bpc(i915);
> > +	dsc_max_bpc = intel_dp_dsc_max_src_input_bpc(i915);
> Seems like this change could have been a part of the previous patch.

Hi Suraj,

Previous patch was only using helpers to get src_min_max dsc bpc for dp 
mst case.

Regards,

Ankit


> Regards,
> Suraj Kandpal
> > +
> > +	dsc_max_bpc = intel_dp_dsc_limit_max_bpc(conn_state-
> > > max_requested_bpc,
> > +						 dsc_max_bpc, dsc_min_bpc);
> >
> >   	dsc_max_pipe_bpp = min(dsc_max_bpc * 3, limits->pipe.max_bpp);
> >   	dsc_min_pipe_bpp = max(dsc_min_bpc * 3, limits->pipe.min_bpp);
> > @@ -2020,14 +2034,14 @@ static int intel_dp_dsc_compute_pipe_bpp(struct
> > intel_dp *intel_dp,
> >   		}
> >   	}
> >
> > +	dsc_min_bpc = intel_dp_dsc_min_src_input_bpc(i915);
> >   	dsc_max_bpc = intel_dp_dsc_max_src_input_bpc(i915);
> >   	if (!dsc_max_bpc)
> >   		return -EINVAL;
> >
> > -	dsc_max_bpc = min_t(u8, dsc_max_bpc, max_req_bpc);
> > +	dsc_max_bpc = intel_dp_dsc_limit_max_bpc(max_req_bpc,
> > dsc_max_bpc,
> > +dsc_min_bpc);
> >   	dsc_max_bpp = min(dsc_max_bpc * 3, limits->pipe.max_bpp);
> >
> > -	dsc_min_bpc = intel_dp_dsc_min_src_input_bpc(i915);
> >   	dsc_min_bpp = max(dsc_min_bpc * 3, limits->pipe.min_bpp);
> >
> >   	/*
> > --
> > 2.40.1