Re: [PATCH v8 6/9] drm/msm/dp: don't take extra references on multiple plug events

[Yongxing Mou <yongxing.mou@oss.qualcomm.com>]

On 10/24/2026 8:35 AM, Dmitry Baryshkov wrote:
> The upper layers might signal multiple sequential HPD plug events. Don't
> take extra references and skip all further HPD plug events until we
> receive the unplug event.
> 
> Fixes: 3ea2d1c3d154 ("drm/msm/dp: turn link_ready into plugged")
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index fa8942922b53..ce919a26fba2 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -412,6 +412,9 @@ static int msm_dp_hpd_plug_handle(struct msm_dp_display_private *dp)
>   
>   	guard(mutex)(&dp->plugged_lock);
>   
> +	if (dp->plugged)
> +		return 0;
> +
>   	ret = pm_runtime_resume_and_get(&pdev->dev);
>   	if (ret) {
>   		DRM_ERROR("failed to pm_runtime_resume\n");
> 
Hi, the issue reported by the AI is real. There is a regression in the 
SST case: when .detect() runs first, it sets plugged to true. As a 
result, when msm_dp_hpd_plug_handle() is called, 
msm_dp_display_process_hpd_high() is skipped, which causes the 
subsequent failure.

I tried removing the plugged update from .detect(), and that fixes the 
SST issue. The display works now. However, there is still an 
intermittent issue where the wrong resolution is selected. I suspect 
this is related to the timing of the EDID read: when fbcon comes up, the 
correct EDID may not be available immediately.