[Intel-gfx] [PATCH 1/3] i915/display/intel_dp: Read PCON DSC ENC caps only for DPCD rev >= 1.4

[Navare, Manasi]

On Fri, Feb 05, 2021 at 10:06:48PM +0200, Ville Syrjälä wrote:
> On Fri, Feb 05, 2021 at 12:07:41PM -0800, Navare, Manasi wrote:
> > On Fri, Feb 05, 2021 at 09:58:07PM +0200, Ville Syrjälä wrote:
> > > On Thu, Feb 04, 2021 at 12:18:40PM +0530, Ankit Nautiyal wrote:
> > > > DP-HDMI2.1 PCON has DSC encoder caps defined in registers 0x92-0x9E.
> > > > Do not read the registers if DPCD rev < 1.4.
> > > > 
> > > > Fixes: https://gitlab.freedesktop.org/drm/intel/-/issues/2868
> > > > Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/display/intel_dp.c | 4 +++-
> > > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > index 8c12d5375607..2b83f0f433a2 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > @@ -2489,9 +2489,11 @@ static void intel_dp_get_pcon_dsc_cap(struct intel_dp *intel_dp)
> > > >  	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
> > > >  
> > > >  	/* Clear the cached register set to avoid using stale values */
> > > > -
> > > >  	memset(intel_dp->pcon_dsc_dpcd, 0, sizeof(intel_dp->pcon_dsc_dpcd));
> > > >  
> > > > +	if (intel_dp->dpcd[DP_DPCD_REV] < 0x14)
> > > > +		return;
> > > > +
> > > 
> > > Can't check the spec, but makes sense that this stuff is only valid
> > > for recent DCPD revisions.
> > > 
> > > Acked-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Yes checked the DP 1.4 spec and this is correct
> 
> I didn't think this is in the DP spec, but rather some special extra
> spec which I do not have.

Yes I meant just double checked that the DSC support itself from DP 1.4 and hence
makes sense that the PCON DSC regs also from >= 1.4

Manasi

> 
> > 
> > Reviewed-by: Manasi Navare <manasi.d.navare at intel.com>
> > 
> > Manasi
> > 
> > > 
> > > >  	if (drm_dp_dpcd_read(&intel_dp->aux, DP_PCON_DSC_ENCODER,
> > > >  			     intel_dp->pcon_dsc_dpcd,
> > > >  			     sizeof(intel_dp->pcon_dsc_dpcd)) < 0)
> > > > -- 
> > > > 2.29.2
> > > 
> > > -- 
> > > Ville Syrjälä
> > > Intel
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx at lists.freedesktop.org
> > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> -- 
> Ville Syrjälä
> Intel