Re: Screen corruption using radeon kernel driver

[Robin Murphy <robin.murphy@arm.com>]

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@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@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@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.

Robin.