Re: [PATCH 19/19] drm/i915/dp: Always enable AS SDP if supported by source + sink

Nautiyal, Ankit K
2026-03-31T12:07:02Z

On 3/31/2026 1:20 AM, Ville Syrjälä wrote:
> On Mon, Mar 30, 2026 at 09:36:56AM +0530, Ankit Nautiyal wrote:
>> Currently AS SDP is only configured when VRR is enabled. However, other
>> use cases like CMRR, Panel Replay, etc. also send information to the sink
>> via AS SDPs.
>>
>> With optimized guardband, we also need to account for wakeup time and other
>> relevant details that depend on the AS SDP position whenever AS SDP is
>> enabled. If a feature enabling AS SDP gets turned on later (after modeset),
>> the guardband might not be sufficient and may need to increase, triggering
>> a full modeset.
>>
>> To avoid this, always send AS SDP whenever the source and sink both
>> support it.
>>
>> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
>> ---
>> drivers/gpu/drm/i915/display/intel_dp.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
>> index 7da3dee226a0..81be0767927e 100644
>> --- a/drivers/gpu/drm/i915/display/intel_dp.c
>> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
>> @@ -3136,7 +3136,7 @@ static bool intel_dp_can_use_as_sdp(struct intel_dp *intel_dp,
>> if (drm_dp_is_branch(intel_dp->dpcd))
>> return false;
>>
>> - return crtc_state->vrr.enable;
>> + return true;
> I think what we actually want is something like
>
> ...
> if (pr_auxless_alpm &&
> DP_PANEL_REPLAY_ASYNC_VIDEO_TIMING_NOT_SUPPORTED_IN_PR)
> return true;
> return intel_vrr_possible();
> }
>
> That way non-VRR PR panels that don't need the AS SDP to maintain
> the synchronization can avoid the AS SDP, and thus potentially use
> a smaller guardband.

Hmm.. makes sense. I will change this as suggested.

Thanks,

Ankit

>> }
>>
>> static void intel_dp_compute_as_sdp(struct intel_dp *intel_dp,
>> --
>> 2.45.2