amdgpu: Corrupted video on 32 bit systems (possible fix)

[Michel Dänzer]

On 20/01/17 04:44 PM, Nils Holland wrote:
> On Fri, Jan 20, 2017 at 11:47:53AM +0900, Michel Dänzer wrote:
>> On 20/01/17 04:35 AM, Nils Holland wrote:
>>>
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c	2016-12-11 20:17:54.000000000 +0100
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c	2017-01-19 15:38:56.972034489 +0100
>>> @@ -372,6 +372,10 @@
>>>  	if (!drm_arch_can_wc_memory())
>>>  		bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC;
>>>  
>>> +	#ifdef CONFIG_X86_32
>>> +		bo->flags &= ~AMDGPU_GEM_CREATE_CPU_GTT_USWC;
>>> +	#endif
>>> +
>>>  	amdgpu_fill_placement_to_bo(bo, placement);
>>>  	/* Kernel allocation are uninterruptible */
>>>  	r = ttm_bo_init(&adev->mman.bdev, &bo->tbo, size, type,
>>
>> The corresponding code in the radeon driver has changed quite a bit
>> since this original fix. It would be better to bring the amdgpu code in
>> line with the current radeon code.
>>
>>
>>> With this patch, the amdgpu driver works fine for me on my 32 bit
>>> kernel: All graphics output looks the way it's supposed to, even with
>>> full acceleration enabled - great!
>>>
>>> I'd suggest that it might be a good idea to put to apply the above
>>> patch or something similar to the official sources.
>>
>> Indeed. Do you want to create a proper patch and submit it to the
>> amd-gfx mailing list for review? See Documentation/SubmittingPatches for
>> more information.
> 
> Sounds like a good idea! I was a bit heasitant because, to be honest,
> I'm not at all an expert about the code in question and basically only
> saw how you fixed the issue in radeon and thought: "Well, let's see if
> I can do the same thing in amdgpu and if so, if it helps there, too".
> ;-)
> 
> However, since you've said that a 32 bit fix in amdgpu generally seems
> like a good idea,

Actually, unless your CPU can't run 64-bit code, I'd say running a
64-bit kernel would be an overall even better idea for you, even with
32-bit userspace. :) Anyway, this problem clearly needs to be fixed.


> I would indeed use a little time on the weekend to get a proper patch
> ready and submit it for review. Even if the "no wc for x86_32" part is
> probably the only thing it'll contain

I wouldn't bother with that. There is no real reason against bringing it
all over in one go.

> - more of "bringing the amdgpu code in line with the current radeon
> code" might, for the time being, be beyond my capabilities, at least
> if we assume that the code should stay in a sane and working
> condition. ;-)

Don't worry, it's mostly a matter of copy'n'paste, testing on your end,
review and more testing by others. :)


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer