Re: [PATCH 08/14] drm/i915/dp: Add AS SDP support for PR with link ON

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Thu, Feb 26, 2026 at 06:10:34PM +0200, Ville Syrjälä wrote:
> On Mon, Feb 23, 2026 at 07:14:25PM +0530, Ankit Nautiyal wrote:
> > Adaptive Sync SDP (AS SDP) is also used for Panel Replay (PR).
> > For PR with Link ON, the AS SDP version V1 is used. When using
> > AS SDP Version 1, AS SDP payload and parity bytes are all set to zeroes.
> 
> I don't think we should need to transmit any AS SDP in link ON mode.

Hmm, maybe we do. While the DP spec is is extremely confusing here
(mostly just talking about the ALPM+AS SDP combo and ignoring the
link ON case), I think what it might be hinting at is that the sink
tells us whether it needs the AS SDP, via
ASYNC_VIDEO_TIMING_NOT_SUPPORTED_IN_PR.

> 
> > 
> > Bspec: 75639
> > Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> > index d08db4938638..5952db6197cf 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > @@ -3115,7 +3115,8 @@ static bool intel_dp_needs_as_sdp(struct intel_dp *intel_dp,
> >  				  struct intel_crtc_state *crtc_state)
> >  {
> >  	return crtc_state->vrr.enable ||
> > -	       crtc_state->cmrr.enable;
> > +	       crtc_state->cmrr.enable ||
> > +	       crtc_state->has_panel_replay;
> >  }
> >  
> >  static void intel_dp_compute_as_sdp(struct intel_dp *intel_dp,
> > @@ -3137,6 +3138,16 @@ static void intel_dp_compute_as_sdp(struct intel_dp *intel_dp,
> >  	as_sdp->length = 0x9;
> >  	as_sdp->duration_incr_ms = 0;
> >  	as_sdp->version = 0x2;
> > +
> > +	if (crtc_state->vrr.enable)
> > +		as_sdp->version = 0x2;
> 
> I think we rather need some versions checks or something to
> make sure the device actually supports v2. VRR itself shouldn't
> need v2 since the v1 was originally added exactly for VRR+PCON
> use cases. PR+ALPM definitely does need v2, but not sure anything
> else actually needs it.
> 
> > +	else
> > +		as_sdp->version = 0x1;
> > +
> > +	/* No payload data bytes for Version 1 */
> > +	if (as_sdp->version == 0x1)
> > +		return;
> > +
> >  	as_sdp->vtotal = intel_vrr_vmin_vtotal(crtc_state);
> >  
> >  	if (crtc_state->cmrr.enable) {
> > @@ -5005,6 +5016,10 @@ static ssize_t intel_dp_as_sdp_pack(const struct drm_dp_as_sdp *as_sdp,
> >  	sdp->sdp_header.HB2 = as_sdp->version;
> >  	sdp->sdp_header.HB3 = as_sdp->length;
> >  
> > +	/* No Payload Data bytes for Version 1 */
> > +	if (as_sdp->version == 0x1)
> > +		return length;
> > +
> >  	/* Fill AS (Adaptive Sync) SDP Payload */
> >  	sdp->db[0] = as_sdp->mode;
> >  	sdp->db[1] = as_sdp->vtotal & 0xFF;
> > -- 
> > 2.45.2
> 
> -- 
> Ville Syrjälä
> Intel

-- 
Ville Syrjälä
Intel