Re: [PATCH 3/4] drm/i915/psr: Apply Intel DPCD workaround when SDP on prior line used

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Wed, 2026-05-06 at 07:24 +0000, Kandpal, Suraj wrote:
> > Subject: [PATCH 3/4] drm/i915/psr: Apply Intel DPCD workaround when
> > SDP on
> > prior line used
> > 
> > There is Intel specific workaround DPCD address containing
> > workaround for
> > case where SDP is on prior line. Apply this workaround according to
> > values in
> > the offset.
> > 
> > Fixes: 61e887329e33 ("drm/i915/xelpd: Handle PSR2 SDP indication in
> > the prior
> > scanline")
> > Cc: <stable@vger.kernel.org> # v5.15+
> > Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_psr.c | 36
> > +++++++++++++++++++++---
> >  1 file changed, 32 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c
> > b/drivers/gpu/drm/i915/display/intel_psr.c
> > index 1f3f0d35d52a..341186622ed4 100644
> > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > @@ -1385,9 +1385,36 @@ static bool psr2_granularity_check(struct
> > intel_crtc_state *crtc_state,
> >  	return true;
> >  }
> > 
> > -static bool _compute_psr2_sdp_prior_scanline_indication(struct
> > intel_dp
> > *intel_dp,
> > -							struct
> > intel_crtc_state
> > *crtc_state)
> > +static bool apply_scanline_indication_wa(struct intel_crtc_state
> > *crtc_state,
> > +					 struct intel_connector
> > *connector)
> 
> Should the name be apply_scanline_indicate, since you are not
> applying the wa here just sort of checking if it needs to be done

It is actually appying WA. I.e. disabling req_psr2_sdp_prior_scanline
if panel is not inline with the eDP1.4b SDP on prior scanline
implementation in intel HW. What do you think?

BR,
Jouni Högander

> 
> Regards,
> Suraj Kandpal
> 
> >  {
> > +	struct intel_dp *intel_dp = intel_attached_dp(connector);
> > +	u8 early_scanline_support = connector-
> > >dp.psr_caps.intel_wa_dpcd &
> > +
> > 	INTEL_WA_REGISTER_CAPS_PSR2_EARLYSCANLINE_SDP_SUPPORT_MA
> > SK;
> > +
> > +	if (intel_dp->edp_dpcd[0] >= DP_EDP_15)
> > +		return true;
> > +
> > +	switch(early_scanline_support)
> > +	{
> > +	case INTEL_WA_REGISTER_CAPS_FALL_BACK_TO_PSR1:
> > +		crtc_state->req_psr2_sdp_prior_scanline = false;
> > +		return false;
> > +	case INTEL_WA_REGISTER_CAPS_PSR2_WITH_EARLY_SCANLINE:
> > +		return true;
> > +	case INTEL_WA_REGISTER_CAPS_PSR2_WITHOUT_EARLY_SCANLINE:
> > +		crtc_state->req_psr2_sdp_prior_scanline = false;
> > +		return true;
> > +	default:
> > +		MISSING_CASE(early_scanline_support);
> > +		return false;
> > +	}
> > +}
> > +
> > +static bool _compute_psr2_sdp_prior_scanline_indication(struct
> > intel_crtc_state *crtc_state,
> > +							struct
> > intel_connector
> > *connector) {
> > +	struct intel_dp *intel_dp = intel_attached_dp(connector);
> >  	struct intel_display *display =
> > to_intel_display(intel_dp);
> >  	const struct drm_display_mode *adjusted_mode =
> > &crtc_state-
> > > uapi.adjusted_mode;
> >  	u32 hblank_total, hblank_ns, req_ns;
> > @@ -1406,7 +1433,8 @@ static bool
> > _compute_psr2_sdp_prior_scanline_indication(struct intel_dp
> > *intel_d
> >  		return false;
> > 
> >  	crtc_state->req_psr2_sdp_prior_scanline = true;
> > -	return true;
> > +
> > +	return apply_scanline_indication_wa(crtc_state,
> > connector);
> >  }
> > 
> >  static int intel_psr_entry_setup_frames(struct intel_dp *intel_dp,
> > @@ -1687,7
> > +1715,7 @@ static bool intel_sel_update_config_valid(struct
> > intel_crtc_state
> > *crtc_state,
> > 
> > conn_state))
> >  		goto unsupported;
> > 
> > -	if (!_compute_psr2_sdp_prior_scanline_indication(intel_dp,
> > crtc_state)) {
> > +	if
> > (!_compute_psr2_sdp_prior_scanline_indication(crtc_state,
> > +connector)) {
> >  		drm_dbg_kms(display->drm,
> >  			    "Selective update not enabled, SDP
> > indication do not
> > fit in hblank\n");
> >  		goto unsupported;
> > --
> > 2.43.0
>