Re: [v3 1/4] drm/i915/display: Enable periodic AS SDP skip frames

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Mismatch between commit message/comments and display version check for Xe3LPD platforms.
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commit e8820000c4c1f603b4949f4796b99e1267661c09
Author: Uma Shankar <uma.shankar@intel.com>

drm/i915/display: Enable periodic AS SDP skip frames

This commit enables periodic Adaptive-Sync SDP (AS SDP) skip frames to allow
the transcoder to drive the panel down to its minimum refresh rate when Panel
Replay is active. It programs a hardware skip-frame counter in PR_ALPM_CTL
so that one AS SDP is followed by a number of idle frames based on the panel's
refresh rate range.

> diff --git a/drivers/gpu/drm/i915/display/intel_alpm.c b/drivers/gpu/drm/i915/display/intel_alpm.c
> index f1383764b7028..d1f6bb82e35ef 100644
> --- a/drivers/gpu/drm/i915/display/intel_alpm.c
> +++ b/drivers/gpu/drm/i915/display/intel_alpm.c

[ ... ]

> @@ -399,16 +428,37 @@ static void lnl_alpm_configure(struct intel_dp *intel_dp,
>  
>  		if (intel_dp->as_sdp_supported) {
>  			u32 pr_alpm_ctl = get_pr_alpm_as_sdp_transmission_time(crtc_state);
> +			u32 skip_frames = 0;
> +
> +			/*
> +			 * AS SDP skip frames field only exists on Xe3LPD+, and
> +			 * periodic AS SDP is only used when VRR is not actively
> +			 * driving the refresh rate.
> +			 */
> +			if (DISPLAY_VER(display) >= 35 && !crtc_state->vrr.enable)
> +				skip_frames = intel_pr_as_sdp_skip_frames(intel_dp);

[Severity: Medium]
Does this code inadvertently disable the feature on Xe3LPD hardware?

The comment explicitly mentions that the AS SDP skip frames field exists on
Xe3LPD+, which has a display version of 30. However, lnl_alpm_configure()
checks if DISPLAY_VER(display) >= 35.

This mismatch means the skip frame calculation will be bypassed for Xe3LPD
devices (Panther Lake), disabling the optimization on the platform it was
intended for.

Should this version check be updated to 30 instead of 35 to match the comment?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260831125914.1736501-1-uma.shankar@intel.com?part=1