Screen corruption using radeon kernel driver

[Alex Deucher]

On Wed, Nov 30, 2022 at 10:42 AM Robin Murphy <robin.murphy at arm.com> wrote:
>
> On 2022-11-30 14:28, Alex Deucher wrote:
> > On Wed, Nov 30, 2022 at 7:54 AM Robin Murphy <robin.murphy at arm.com> wrote:
> >>
> >> On 2022-11-29 17:11, Mikhail Krylov wrote:
> >>> On Tue, Nov 29, 2022 at 11:05:28AM -0500, Alex Deucher wrote:
> >>>> On Tue, Nov 29, 2022 at 10:59 AM Mikhail Krylov <sqarert at gmail.com> wrote:
> >>>>>
> >>>>> On Tue, Nov 29, 2022 at 09:44:19AM -0500, Alex Deucher wrote:
> >>>>>> 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
> >>>>>
> >>>>> That is ATI Radeon X1950, and, unfortunately, radeon.agpmode=-1 doesn't
> >>>>> help, it just makes 3D acceleration in games such as OpenArena stop
> >>>>> working.
> >>>>
> >>>> Just to confirm, is the board AGP or PCIe?
> >>>>
> >>>> Alex
> >>>
> >>> It is AGP. That's an old machine.
> >>
> >> Can you check whether dma_addressing_limited() is actually returning the
> >> expected result at the point of radeon_ttm_init()? Disabling highmem is
> >> presumably just hiding whatever problem exists, by throwing away all
> >>   >32-bit RAM such that use_dma32 doesn't matter.
> >
> > The device in question only supports a 32 bit DMA mask so
> > dma_addressing_limited() should return true.  Bounce buffers are not
> > really usable on GPUs because they map so much memory.  If
> > dma_addressing_limited() returns false, that would explain it.
>
> Right, it appears to be the only part of the offending commit that
> *could* reasonably make any difference, so I'm primarily wondering if
> dma_get_required_mask() somehow gets confused.

Mikhail,

Can you see that dma_addressing_limited() and dma_get_required_mask()
return in this case?

Alex


>
> Thanks,
> Robin.