3.18-rc regression: drm/nouveau: use shared fences for readable objects

[Tobias Klausmann]

On 19.11.2014 09:10, Maarten Lankhorst wrote:
> Hey,
>
> On 19-11-14 07:43, Michael Marineau wrote:
>> On 3.18-rc kernel's I have been intermittently experiencing GPU
>> lockups shortly after startup, accompanied with one or both of the
>> following errors:
>>
>> nouveau E[   PFIFO][0000:01:00.0] read fault at 0x000734a000 [PTE]
>> from PBDMA0/HOST_CPU on channel 0x007faa3000 [unknown]
>> nouveau E[     DRM] GPU lockup - switching to software fbcon
>>
>> I was able to trace the issue with bisect to commit
>> 809e9447b92ffe1346b2d6ec390e212d5307f61c "drm/nouveau: use shared
>> fences for readable objects". The lockups appear to have cleared up
>> since reverting that and a few related followup commits:
>>
>> 809e9447: "drm/nouveau: use shared fences for readable objects"
>> 055dffdf: "drm/nouveau: bump driver patchlevel to 1.2.1"
>> e3be4c23: "drm/nouveau: specify if interruptible wait is desired in
>> nouveau_fence_sync"
>> 15a996bb: "drm/nouveau: assign fence_chan->name correctly"
> Weird. I'm not sure yet what causes it.
>
> http://cgit.freedesktop.org/~mlankhorst/linux/commit/?h=fixed-fences-for-bisect&id=86be4f216bbb9ea3339843a5658d4c21162c7ee2
>
> On the EDITED patch from fixed-fences-for-bisect, can you do the following:
>
> In nouveau/nv84_fence.c function nv84_fence_context_new, remove
>
> fctx->base.sequence = nv84_fence_read(chan);
>
> and add back
>
> nouveau_bo_wr32(priv->bo, chan->chid * 16/4, 0x00000000);
>
> If that fails you should compile your kernel with trace events, to get some debugging info from the fences. I'll post debugging info if this does not fix it.
>
> ~Maarten

Hey,
as mentioned in IRC the new fencing hangs my GPU for a while as well (nve7).
Bisected back to  86be4f216bbb9ea3339843a5658d4c21162c7ee2
, EDITED

from the fixed-fences-for-bisect branch mentioned above.

Original bisect on linus brach brought me to:
29ba89b2371d466ca68973525816cf10debc2655
drm/nouveau: rework to new fence interface

Michael if you are going to bisect the "fixed-fences-for-bisect" branch, 
maybe take a closer look if you come anywhere near that commit, if that 
does or does not trigger the GPU hangs for you!

Tobias