[Nouveau] drm-nouveau-next - write trapped by fbcon

[Ilia Mirkin]

On Wed, Dec 11, 2013 at 6:43 AM, Bruno Prémont
<bonbons at linux-vserver.org> wrote:
> Hi Ilia,
>
>> On Thu, 5 Dec 2013 10:55:06 -0500 Ilia Mirkin wrote:
>> > On Thu, Dec 5, 2013 at 10:17 AM, Bruno Prémont wrote:
>> > > With drm-nouveau-next branch on top of 3.13-rc2 and a few sound commits
>> > > I get following errors in kernel log (repeating much more often).
>> > > (once there was a corrupted fbcon with matrix-like strings of
>> > > unrecognizable glyph-strings hanging down from screen top border)
>> > >
>> > > These errors do stop once I switch to Xorg.
>> > >
>> > > [   13.825627] nouveau E[     PFB][0000:02:00.0] trapped write at 0x0000408280 on channel 0x0000fee0 [unknown] BAR/PFIFO_WRITE/FB reason: PAGE_NOT_PRESENT
>> > > [   13.826506] nouveau E[     PFB][0000:02:00.0] trapped write at 0x0000408280 on channel 0x0000fee0 [unknown] BAR/PFIFO_WRITE/FB reason: PAGE_NOT_PRESENT
>> > > [   13.827319] nouveau E[     PFB][0000:02:00.0] trapped write at 0x0000408280 on channel 0x0000fee0 [unknown] BAR/PFIFO_WRITE/FB reason: PAGE_NOT_PRESENT
>> > > [   13.828139] nouveau E[     PFB][0000:02:00.0] trapped write at 0x0000408280 on channel 0x0000fee0 [unknown] BAR/PFIFO_WRITE/FB reason: PAGE_NOT_PRESENT
>> > > [   13.828957] nouveau E[     PFB][0000:02:00.0] trapped write at 0x0000400300 on channel 0x0000fee0 [unknown] BAR/PFIFO_WRITE/FB reason: PAGE_NOT_PRESENT
>> > >
>> > > System MBA2,1 with:
>> > > 02:00.0 VGA compatible controller [0300]: NVIDIA Corporation C79 [GeForce 9400M] [10de:0870] (rev b1)
>> >
>> > Do you also see these in 3.13-rc2 +
>> > http://cgit.freedesktop.org/nouveau/linux-2.6/commit/?h=drm-nouveau-next&id=a7e4201f0f7d47e03b851f06f8987856e8d33083
>> > ? If not, you can reorder the patches (git rebase -i) and bisect the
>> > rest. Basically the GPU is trying to write to some address that is
>> > either completely bogus or is stale, and its internal MMU won't let
>> > it.
>>
>> If I remember correctly these did not happen with Linus' rc2 but only
>> do happen with drm-nouveau-next on top of it.
>>
>> I will check and bisect though probably will not get time to complete
>> bisect before late Saturday.
>>
>>
>> A display glitch during kernel boot with fbcon might be related to this.
>> (very wild guess based on when the trapped writes happen)
>> The penguin logo shown by fbcon looks like memcopy'ed to a tiled
>> framebuffer without respecting the fact that framebuffer is tiled.
>
> It was introduced somewhere between 3.12 and 3.13-rc2 though does not happen
> on every boot and when it happens it might be only a couple of trapped writes
> or a whole lot flooding complete log buffer.
>
> Visually it manifests itself as a scrambled framebuffer
> (looking like tiled versus untiled writing to framebuffer).
> When it happens, it seem to be correlated to call to dialog to ask for
> luks password and screen scrambling happens when boot messages
> (kernel/userspace) show/scroll by [they wipe out some scrambled area
> when scrolling by].
>
> Unfortunately it will be rather hard to bisect because sometimes it does not
> happen.
> Adding drm-nouveau-next on top of rc2/rc3 does no apparent difference.

A shot in the dark -- try booting with nouveau.config=NvMSI=0. We
already disable MSI for NVAA, perhaps we should do it for NVAC as
well. Although the blob drivers have it enabled... but we could be
doing something wrong.

  -ilia