Screen corruption using radeon kernel driver

[Alex Deucher]

On Mon, Nov 28, 2022 at 3:48 PM Mikhail Krylov <sqarert at gmail.com> wrote:
>
> On Mon, Nov 28, 2022 at 09:50:50AM -0500, Alex Deucher wrote:
>
> >>> [excessive quoting removed]
>
> >> 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?
> >>
> > On Mon, Nov 28, 2022 at 9:31 AM Mikhail Krylov <sqarert at gmail.com> wrote:
> > Unless someone familiar with HIMEM can figure out what is going wrong
> > we should just revert the patch.
> >
> > Alex
>
>
> Okay, I was suggesting that mostly because
>
> a) it works for me with dma_bits = 40 (I understand that's what it is
> without the original patch applied);
>
> b) there's a hint of uncertainity on this line
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/radeon/radeon_device.c#n1359
> saying that for AGP dma_bits = 32 is the safest option, so apparently there are
> setups, unlike mine, where dma_bits = 32 is better than 40.
>
> But I'm in no position to argue, just wanted to make myself clear.
> I'm okay with rebuilding the kernel for my machine until the original
> patch is reverted or any other fix is applied.

What GPU do you have and is it AGP?  If it is AGP, does setting
radeon.agpmode=-1 also fix it?

Alex