Re: [PATCH] drm/msm/dpu: delete timeout timer when encoder is not busy

[Jun Nie]

Jun Nie <jun.nie@xxxxxxxxxx> 于2026年9月3日周四 22:30写道：
>
> There is a spurious timeout error message under the following reproduction
> steps:
> 1. Run "modetest -M msm -r" and press CTRL+Z to pause it.
> 2. Run "while true; do rtcwake -m mem -s 3 -v; sleep 2; done"
>
> Resulting error message:
> [  124.018206] [drm:dpu_encoder_virt_atomic_disable:1425] [dpu error]enc35 timeout pending
>
> dpu_crtc_commit_kickoff() calls dpu_encoder_kickoff() to set frame busy
> bits, and then arms the frame done timer. If the frame done IRQ fires
> between these two steps, the IRQ handler clears the busy bits before the
> timer is armed. As a result, the timer runs with busy bits already cleared
> and is never cancelled by subsequent IRQ handlers, leading to a false
> timeout warning.
>
> Delete the pending timer when all busy bits are cleared in the frame done
> callback to prevent false timeouts.
>

Another option is to wrap the enc_spinlock lock/unlock pair in dpu_encoder.c
and expose it to dpu_crtc.c to make the sequence of dpu_encoder_kickoff()
and dpu_encoder_start_frame_done_timer() atomic against the IRQ handler.
However, this breaks encoder self-containment to some extent. Furthermore,
initial testing revealed a deadlock involving additional locks beyond
dpu_enc->enc_spinlock.

- Jun