Linux 5.16.3 breaks headless Raspberry Pi 3 boot, again

[Maxime Ripard]

Hi,

On Sun, Jan 30, 2022 at 03:57:07PM +0100, Michael Stapelberg wrote:
> Hello again,
> 
> I am facing the exact same symptoms as last September:
> https://lists.freedesktop.org/archives/dri-devel/2021-September/324008.html
> 
> …meaning my (headless) Raspberry Pi 3 B and Raspberry Pi 3 B+ no longer
> boot with Linux 5.16.3, while the (headless) Raspberry Pi 4 still boots.

I'm not entirely sure what you expect by insisting on things getting
broken *again*, but we got it, thanks.

> This issue is not fixed with the latest Linux 5.16.4 either.
> 
> If needed, I can git-bisect it, but perhaps you have a hunch already?
> 
> With 5.16.2 (working), I see the following serial console output:
> [    2.493456] fb0: switching to vc4 from simple
> [    2.500306] Console: switching to colour dummy device 80x25
> [    2.507204] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on minor 0
> [    2.517617] vc4-drm soc:gpu: [drm] Cannot find any crtc or sizes
> [   12.517962] vc4-drm soc:gpu: [drm] Cannot find any crtc or sizes
> 
> With 5.16.3 (broken), I see:
> [    2.485311] fb0: switching to vc4 from simple
> [    2.492167] Console: switching to colour dummy device 80x25
> [    2.499148] [drm] Initialized vc4 0.0.0 20140616 for soc:gpu on minor 0
> <boot hangs>

I bisected it, and it looks like it's because of a bad conflict
resolution in stable.

The original commit is here:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=20b0dfa86bef0e80b41b0e5ac38b92f23b6f27f9

And the stable commit is here:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9b0d360fd783c711fc1cafa51f3e03bdf8ca5518

For some reason, in the stable commit, pm_runtime_put ended up in
vc4_hdmi_cec_init while it should have been at the end of
vc4_hdmi_cec_adap_enable.

I'll send a patch to fix it.

Maxime
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