> -----Original Message-----
> From: Jani Nikula <[email protected]>
> Sent: Monday, August 12, 2024 5:24 PM
> To: Borah, Chaitanya Kumar <[email protected]>; intel-
> [email protected]; [email protected]
> Cc: Deak, Imre <[email protected]>; Borah, Chaitanya Kumar
> <[email protected]>
> Subject: Re: [PATCH] drm/i915: Preserve value of fec_enable calculated before
> DSC compute config
>
> On Mon, 12 Aug 2024, Chaitanya Kumar Borah
> <[email protected]> wrote:
> > Before DSC compute config, fec_enable value is set in other functions
> > (e.g. intel_dp_mst_find_vcpi_slots_for_bpp). We are ignoring the value
> > by OR'ing its value in DSC compute config. One unintended effect of
> > this is setting fec_enable in UHBR use-cases which is not needed for
> > Intel hardware. Therefore, change operator to AND.
> >
> > While at it, add a comment explaining why we don't enable FEC in eDP v1.5.
> >
> > Signed-off-by: Chaitanya Kumar Borah <[email protected]>
> > ---
> > drivers/gpu/drm/i915/display/intel_dp.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > b/drivers/gpu/drm/i915/display/intel_dp.c
> > index 49a37b996530..3fbf9f33c3e4 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -2298,7 +2298,12 @@ int intel_dp_dsc_compute_config(struct
> intel_dp *intel_dp,
> > &pipe_config->hw.adjusted_mode;
> > int ret;
> >
> > - pipe_config->fec_enable = pipe_config->fec_enable ||
> > + /*
> > + * Though eDP v1.5 supports FEC with DSC, unlike DP, it is optional.
> > + * Since, FEC is a bandwidth overhead, continue to not enable it for
> > + * eDP. Until, there is a good reason to do so.
> > + */
> > + pipe_config->fec_enable = pipe_config->fec_enable &&
> > (!intel_dp_is_edp(intel_dp) &&
> > intel_dp_supports_fec(intel_dp, connector, pipe_config));
>
> With this change, FEC will only be enabled for non-UHBR MST DP and nothing
> else. This is the place where SST DP DSC gets FEC enabled.
Thank you Jani for pointing it out.
Something like this should work?
pipe_config->fec_enable = pipe_config->fec_enable ||
(!intel_dp_is_edp(intel_dp) &&
intel_dp_supports_fec(intel_dp, connector, pipe_config) &&
!intel_dp_is_uhbr(pipe_config));
Regards
Chaitanya
>
> BR,
> Jani.
>
>
> --
> Jani Nikula, Intel
