[PATCH 1/3] drm/radeon: stop poisoning the GART TLB

[Christian König]

Hi Marek,

> There is a workaround in 3.15 which disables sDMA and uses CP DMA for
> copying buffers. It seems to help Christian's machine, but not mine.
With stressing the box with piglit I was able to bring my machine down 
with the CP DMA as well, only cherry-picking the "stop poisoning the 
GART TLB" really fixed that issue.

But I'm pretty sure that even with "stop poisoning the GART TLB" 
back-ported we still have at least one stability issue I can't reproduce.

Christian.

Am 19.06.2014 12:20, schrieb Marek Olšák:
> Hi Michel,
>
> 3.15 doesn't contain Christian's fix yet, so it should be always
> broken for everybody. The fix is currently only in 3.16.
>
> Alternatively, you can cherry-pick the fix to 3.15, but it doesn't
> apply cleanly.
>
> There is a workaround in 3.15 which disables sDMA and uses CP DMA for
> copying buffers. It seems to help Christian's machine, but not mine.
>
> When I said the kernel driver was broken, I meant that
> it was broken *with* the fix applied regardless of which engine was
> used for the copying.
>
> Marek
>
> On Thu, Jun 19, 2014 at 3:48 AM, Michel Dänzer <michel at daenzer.net> wrote:
>> On 15.06.2014 21:48, Christian König wrote:
>>> Am 13.06.2014 23:31, schrieb Alex Deucher:
>>>> On Fri, Jun 13, 2014 at 11:45 AM, Christian König
>>>> <deathsimple at vodafone.de> wrote:
>>>>> Hi Marek,
>>>>>
>>>>> ah, yes! Piglit in combination with that patch can indeed crash the box.
>>>>>
>>>>> Going to investigate now that I can reproduce it.
>>>> I wonder if it's a clockgating issue with the MC or BIF?  You might
>>>> try adjusting the rdev->cg_flags (try setting it to 0) in
>>>> radeon_asic.c or disabling dpm.
>>> Unfortunately that was just a false alarm.
>>>
>>> I was just on a branch which didn't had the "stop poisoning the GART
>>> TLB" patch, after applying this patch I can again let piglit run for the
>>> whole night without a lockup.
>>>
>>> No idea what goes wrong when Marek runs piglit, but 3.15.0+"stop
>>> poisoning the GART TLB"+"force_gtt" is rock solid here.
>> FWIW, 3.15 doesn't survive piglit on my Bonaire either, but 3.14 is
>> fine. 3.15 seems stable on Kaveri though, but I haven't tried the
>> force_gtt patch on that yet.
>>
>> There have also been a number of bug reports about stability regressions
>> in 3.15 on various SI and CIK cards. It seems likely that at least some
>> of those are related to this issue as well.
>>
>> If we can't figure out the problem soon, we probably need to revert the
>> 'Use normal BOs for page tables' and dependent changes at least for 3.15.y?
>>
>>
>> --
>> Earthling Michel Dänzer            |                  http://www.amd.com
>> Libre software enthusiast          |                Mesa and X developer
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