Screen corruption using radeon kernel driver

[Alex Deucher]

+ dri-devel

On Mon, Apr 25, 2022 at 3:33 AM Krylov Michael <sqarert at gmail.com> wrote:
>
> Hello!
>
> After updating my Linux kernel from version 4.19 (Debian 10 version) to
> 5.10 (packaged with Debian 11), I've noticed that the image
> displayed on my older computer, 32-bit Pentium 4 using ATI Radeon X1950
> AGP video card is severely corrupted in the graphical (Xorg and Wayland)
> mode: all kinds of black and white stripes across the screen, some
> letters missing, etc.
>
> I've checked several options (Xorg drivers, Wayland instead of
> Xorg, radeon.agpmode=-1 in kernel command line and so on), but the
> problem persisted. I've managed to find that the problem was in the
> kernel, as everything worked well with 4.19 kernel with everything
> else being from Debian 11.
>
> I have managed to find the culprit of that corruption, that is the
> commit 33b3ad3788aba846fc8b9a065fe2685a0b64f713 on the linux kernel.
> Reverting this commit and building the kernel with that commit reverted
> fixes the problem. Disabling HIMEM also gets rid of that problem. But it
> also leaves the system with less that 1G of RAM, which is, of course,
> undesirable.
>
> Apparently this problem is somewhat known, as I can tell after googling
> for the commit id, see this link for example:
> https://lkml.org/lkml/2020/1/9/518
>
> Mageia distro, for example, reverted this commit in the kernel they are
> building:
>
> http://sophie.zarb.org/distrib/Mageia/7/i586/by-pkgid/b9193a4f85192bc57f4d770fb9bb399c/files/32
>
> I've reported this bug to Debian bugtracker, checked the recent verion
> of the kernel (5.17), bug still persists. Here's a link to the Debian
> bug page:
>
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=993670
>
> I'm not sure if reverting this commit is the correct way to go, so if
> you need to check any changes/patches that I could apply and test on
> the real hardware, I'll be glad to do that (but please keep in mind
> that testing could take some time, I don't have access to this computer
> 24/7, but I'll do my best to respond ASAP).

I would be happy to revert that commit.  I attempted to revert it a
year or so ago, but Christoph didn't want to.  He was going to look
further into it.  I was not able to repro the issue.  It seemed to be
related to highmem support.  You might try disabling that.  Here is
the previous thread for reference:
https://lists.freedesktop.org/archives/amd-gfx/2020-September/053922.html

Alex