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

From: Peter Mattern <pmattern@arcor.de>
To: dri-devel@lists.freedesktop.org
Subject: drm/vc4: module dysfunctional on Raspberry Pi 3B as of 5.18.0
Date: Thu, 9 Jun 2022 14:49:20 +0200	[thread overview]
Message-ID: <5d81e922-fa5b-7a81-0e91-7f79a3646289@arcor.de> (raw)

 > Which kernel config do you use (is it a defconfig)?
These are custom configs provided by the distribution, the origin of 
which I do not know.
You can find them at [1] (5.17.0, used in 5.17.1 as well) and [2] 
(5.18.0, modified in 5.18.1).
The difference between these files and their upstream (kernel.org) 
counterpart as created by running 'make ARCH=arm64 defconfig' is about 
11k lines, the difference between the two files of the distribution 
around 800 lines. Didn't investigate the differences in detail yet.

 > Do you use the mainline device tree blob or the Raspberry Pi DTB?
It's the one from the kernel.org sources.
Note: At times you'll find claims that the DTBs of the Raspberry Pi 
Foundation were used on Arch Linux ARM. These probably are due to the 
fact that those blobs happen to be around. But U-Boot's boot.scr does 
pick the "mainline" ones in /boot/dtbs/.

 > Please provide the version/date of the GPU firmware?
It is provided by the Broadcom bootloader package (which is used to 
chainload U-Boot). It happened to be updated in parallel with kernel 
5.18.0 to commit f145afcf [3] and has since been updated to upstream 
commit 8f91a969. Those latest changes don't seem to have an impact on 
the problem we're discussing here (not all combinations bootloader / 
kernel tested).

 > Do you have any KMS related setting in the config.txt?
No.
My epic config.txt is: enable_uart=1

 > Can you provide a full dmesg for the bad case?
I sure could. But grepping through it yields the exact same results 
included in my first post. And assuming this list scrubs attachments I'm 
not sure whether posting those 500 lines in a mail would make sense?

[1] 
https://github.com/archlinuxarm/PKGBUILDs/blob/ae861a830e6e1d6d3e37c94462c8f48671aa9b79/core/linux-aarch64/config
[2] 
https://github.com/archlinuxarm/PKGBUILDs/blob/9c5b51b25ecc038cd505b26e15bb80464783a713/core/linux-aarch64/config
[3] 
https://github.com/archlinuxarm/PKGBUILDs/blob/722080b0aaa7e158d91b323d27c41839d1ef42f0/alarm/raspberrypi-bootloader/PKGBUILD