[Nouveau] Trouble with TTM patches w/nouveau in linux-next

[Christian König]

Good point, but I think that is unrelated.

My suspicion is rather that nouveau is not initializing the underlying 
GEM object for internal allocations.

So what happens is the same as on VMWGFX that TTM doesn't know anything 
about the size to of the BO resulting in a kmalloc() with a random value 
and eventually -ENOMEM.

Good news is that I can reproduce it, so going to look into that later 
today.

Regards,
Christian.

Am 09.06.21 um 16:52 schrieb Ilia Mirkin:
> Christian - potentially relevant is that Tegra doesn't have VRAM at
> all -- all GTT (or GART or whatever it's called nowadays). No
> fake/stolen VRAM.
>
> Cheers,
>
>    -ilia
>
> On Wed, Jun 9, 2021 at 10:18 AM Christian König
> <christian.koenig at amd.com> wrote:
>> Hi Mikko,
>>
>> strange sounds like Nouveau was somehow also using the GEM workaround
>> for VMWGFX as well.
>>
>> But -12 means -ENOMEM which doesn't fits into the picture.
>>
>> I will try with a G710, but if that doesn't yields anything I need some
>> more input from you.
>>
>> Thanks for the report,
>> Christian.
>>
>>
>> Am 09.06.21 um 15:47 schrieb Mikko Perttunen:
>>> Hi,
>>>
>>> I'm observing nouveau not initializing recently on linux-next on my
>>> Tegra186 Jetson TX2 board. Specifically it looks like BO allocation is
>>> failing when initializing the sync subsystem:
>>>
>>> [   21.858149] nouveau 17000000.gpu: DRM: failed to initialise sync
>>> subsystem, -28
>>>
>>> I have been bisecting and I have found two patches that affect this.
>>> Firstly, things first break on
>>>
>>> d02117f8efaa drm/ttm: remove special handling for non GEM drivers
>>>
>>> starting to return error code -12. Then, at
>>>
>>> d79025c7f5e3 drm/ttm: always initialize the full ttm_resource v2
>>>
>>> the error code changes to the above -28.
>>>
>>> If I checkout one commit prior to d79025c7f5e3 and revert
>>> d02117f8efaa, things work again. There are a bunch of other TTM
>>> commits between this and HEAD, so reverting these on top of HEAD
>>> doesn't work. However, I checked that both yesterday's and today's
>>> nexts are also broken.
>>>
>>> Thank you,
>>> Mikko
>>>
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