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

[Bruno Prémont]

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.

Bruno