Re: [PATCH] drm/i915/dp: Only send AS SDP when VRR is enabled or PR !async

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/i915/dp: AS SDP transmission disabled for CMRR
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commit ec709d876da894a1dbf999ecfaaa9f0515c311ce
Author: Xizhe Tang <xizheTang2005@163.com>

drm/i915/dp: Only send AS SDP when VRR is enabled or PR !async

This commit changes the terminal condition for transmitting the
Adaptive-Sync SDP on DP links from intel_vrr_possible() to
crtc_state->vrr.enable, avoiding sending the AS SDP to fixed-refresh
links that merely advertise VRR capability.

Link: https://gitlab.freedesktop.org/drm/xe/kernel/-/work_items/9252

> diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c
> --- a/drivers/gpu/drm/i915/display/intel_dp.c
> +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> @@ -3113,7 +3113,7 @@ static bool intel_dp_needs_as_sdp(struct intel_dp *intel_dp,
>  	    !intel_psr_pr_async_video_timing_supported(intel_dp))
>  		return true;
>  
> -	return intel_vrr_possible(crtc_state);
> +	return crtc_state->vrr.enable;

[Severity: High]
Does this inadvertently disable AS SDP transmission when Continuous Mode
Refresh Rate (CMRR) is active?

When CMRR is configured on the fixed refresh rate path, it sets
crtc_state->vrr.cmrr.enable to true, but crtc_state->vrr.enable is left as
false. Returning crtc_state->vrr.enable here evaluates to false for CMRR,
causing intel_dp_needs_as_sdp() to skip AS SDP transmission and breaking
CMRR synchronization.

Consequently, in intel_dp_compute_as_sdp() this leads to unreachable code:

intel_dp_compute_as_sdp() {
    ...
    if (!intel_dp_needs_as_sdp(intel_dp, crtc_state))
        return;
    ...
    if (crtc_state->vrr.cmrr.enable) {
        as_sdp->mode = DP_AS_SDP_FAVT_TRR_REACHED;
        ...

The CMRR configuration block becomes dead code because the function
exits early when vrr.enable is false.

Should this condition also check for crtc_state->vrr.cmrr.enable to
ensure AS SDP is still transmitted for CMRR?

>  }

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Sashiko AI review · https://sashiko.dev/#/patchset/20260923052937.22817-1-xizheTang2005@163.com?part=1