drm/vc4: module dysfunctional on Raspberry Pi 3B as of 5.18.0

[Maxime Ripard]

On Wed, Jun 08, 2022 at 05:36:08PM +0200, Maxime Ripard wrote:
> On Wed, Jun 08, 2022 at 04:14:22PM +0100, Peter Robinson wrote:
> > > > > As of Linux 5.18.0, module vc4 apparently isn't working on Raspberry Pi
> > > > > 3B any more.
> > > > >
> > > > > If a monitor is attached to the device, the boot messages show up as
> > > > > usual, but right when KMS starts, the screen turns black. Similarly, the
> > > > > screen also turns black when the module is blacklisted at boot time and
> > > > > loaded from the running system.
> > > > > The problem looks quite similar to the one posted some months ago in [1].
> > >
> > > If I understand you properly, it results in a blank screen if the
> > > monitor is connected, but the system is still responsive?
> > 
> > Yes, it boots fine, I see all serial console output and the module
> > loads etc, without a screen I didn't notice the issue
> > 
> > > If so, it's a very different problem than the link you provided, since
> > > it was occurring when no monitor was connected and resulted in a total
> > > system hang.
> > >
> > > > > Unfortunately, looking through systemd's journal didn't seem to yield
> > > > > any real hint. Nevertheless, the results from grepping vc4 are
> > > >
> > > > I'm seeing the same issue with vc4 on a RPi3 on 5.18.1 on Fedora so
> > > > can confirm the regression. Maxime would know what might be up here?
> > >
> > > I tested on 5.18 on my 3B and it works well. Could you paste your kernel
> > > configuration and config.txt somewhere?
> > 
> > It boots with output on 5.17.13, and not on 5.18.
> 
> Interestingly, it works for 5.18 in my case but doesn't for the current
> drm-misc-next branch with similar symptoms.
> 
> I'll look into that one and see if the two might be related.

Actually, it was because drm-misc-next was missing 88110a9f6209, and
thus the DRM driver wouldn't load.

Once that patch is applied, 5.18 and all -rc work fine on my side.

Could you start a bisection maybe?

Maxime
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