[BUG] VC4 DRM waiting for flip down makes UI freeze a while with kernel 5.15

[Maxime Ripard]

Hi,

On Fri, Nov 12, 2021 at 11:22:49AM +0800, Jian-Hong Pan wrote:
> Hi,
> 
> I tested Linux mainline kernel 5.15 (aarch64) with enabled VC4 on RPi 4B. I
> notice UI freezes a while (about 10 seconds) some times.
> 
> The kernel shows the error message during the time:
> 
> [drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
> [drm:drm_atomic_helper_wait_for_flip_done] *ERROR* [CRTC:68:crtc-3]
> flip_done timed out
> [drm:drm_atomic_helper_wait_for_dependencies] *ERROR* [CRTC:68:crtc-3]
> commit wait timed out
> [drm:drm_crtc_commit_wait] *ERROR* flip_done timed out
> vc4-drm gpu: [drm] *ERROR* Timed out waiting for commit
> 
> Here is the full log:
> https://github.com/lategoodbye/rpi-zero/files/7518076/dmesg-5.15.log
> 
> It is easy to reproduce this issue by invoking GL related things, for
> example "es2gears".
> 
> After detail test, I found it is related to these commits:
> * f3c420fe19f8 ("drm/vc4: kms: Convert to atomic helpers")
> * 82faa3276012 ("drm/vc4: kms: Remove async modeset semaphore")
> 
> This issue cannot be reproduced after I revert the commits.

I've been working on those regressions recently, and just sent all the
fixes I have so far:
https://lore.kernel.org/dri-devel/20211115113105.103275-1-maxime@cerno.tech/

Based on the symptoms you provided, I think it should be fixed with
those patches

Let me know how it goes
Maxime
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