Screen corruption using radeon kernel driver

[Alex Deucher]

On Mon, Nov 28, 2022 at 9:31 AM Mikhail Krylov <sqarert at gmail.com> wrote:
>
> On Mon, Apr 25, 2022 at 01:22:04PM -0400, Alex Deucher wrote:
> > + 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
>
> So, is there any progress on this issue? I do understand it's not a high
> priority one, and today I've checked it on 6.0 kernel, and
> unfortunately, it still persists...
>
> I'm considering writing a patch that will allow user to override
> need_dma32/dma_bits setting with a module parameter. I'll have some time
> after the New Year for that.
>
> Is it at all possible that such a patch will be merged into kernel?

Unless someone familiar with HIMEM can figure out what is going wrong
we should just revert the patch.

Alex