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

[Stefan Wahren]

Hi,

Am 09.06.22 um 23:33 schrieb Stefan Wahren:
> Hi Peter,
>
> Am 09.06.22 um 13:52 schrieb Peter Robinson:
>>>>>> 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?
>>>>
>>>> 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 assume you are using the downstream DTB?
>> In this case it's the one in the Linux kernel (not sure if that's
>> upstream or downstream in this context) not the one provided by the
>> RPi firmware.
>
> okay thanks. I tried the kernel config but its huge.
>
> Is it correct that the issue occurs with your kernel config, but not 
> with multi_v7_defconfig?

FWIW here is what i tried to reproduce the issue:

- enable CONFIG_DRM_VC4_HDMI_CEC
- apply the relevant config.txt options from Peter R.
- update my gcc toolchain to 11.3
- switch compiler optimization from speed to size

But the display always works.

Please tell the size of your bcm2837-rpi-3-b.dtb