[Nouveau] Tracking down severe regression in 5.3-rc4/5.4 for TU116 - assistance needed

[Ilia Mirkin]

The obvious candidate based on a quick scan is
0acf5676dc0ffe0683543a20d5ecbd112af5b8ee -- it merges a fix that
messes with PCI stuff, and there lie dragons. You could try building
that commit, and if things still work, then I have no idea (and you've
narrowed the range). Also I'd recommend ensuring that the good kernel
is really good and the bad kernel is really bad -- boot them a few
times.

Cheers,

  -ilia

On Mon, Dec 16, 2019 at 12:42 PM Marcin Zajączkowski <mszpak at wp.pl> wrote:
>
> On 2019-12-16 18:08, Ilia Mirkin wrote:
> > Hi Marcin,
> >
> > You should do a git bisect rather than guessing about commits. I
> > suspect that searching for "kernel git bisect fedora" should prove
> > instructive if you're not sure how to do this.
>
> Thanks for your suggestion. I realize that I can do it at the Git level
> and it is the ultimate way to go. However, building the kernel version
> from sources takes some time (in addition to a regular time needed to
> install/restart/verify which I already experienced narrowing down to a
> "just" ~250 commits).
>
> Therefore, I would be really thankful for a suggestion which commits
> could be good to check first - having 2, 4 is better than 8-10 (assuming
> someone is right :) ).
>
> Marcin
>
>
>
> > On Mon, Dec 16, 2019 at 11:42 AM Marcin Zajączkowski <mszpak at wp.pl> wrote:
> >>
> >> Hi,
> >>
> >> I've encountered a severe regression in TU116 (probably also TU117)
> >> introduced in 5.3-rc4 (valid also for recent 5.4.2) [1]. The system
> >> usually hangs on the subsequent graphic mode related operation (calling
> >> xrandr after login is enough) with the following error:
> >>
> >>> kernel: nouveau 0000:01:00.0: fifo: SCHED_ERROR 08 []
> >> ...
> >>> kernel: nouveau 0000:01:00.0: DRM: failed to idle channel 0 [DRM]
> >>> kernel: nouveau 0000:01:00.0: i2c: aux 0007: begin idle timeout ffffffff
> >>> kernel: nouveau 0000:01:00.0: tmr: stalled at ffffffffffffffff
> >>> kernel: ------------[ cut here ]------------
> >>> kernel: nouveau 0000:01:00.0: timeout
> >>> kernel: WARNING: CPU: 10 PID: 384 at drivers/gpu/drm/nouveau/nvkm/subdev/bar/g84.c:35 g84_bar_flush+0xcf/> 0xe0 [nouveau]
> >>
> >> (detailed log in a corresponding issue - [1])
> >>
> >> With earlier kernels there was no hardware acceleration for NVidia GTX
> >> 1660 Ti, but at least I could use nouveau to disable it (to save
> >> battery, trees and lower temperature) or even have an external output
> >> (with Wayland). Now, the system is unusable with nouveau :(.
> >>
> >> I spent some time trying to narrow the scope using on the existing
> >> kernel builds for Fedora. I was able to determine that the problem was
> >> introduced between 5.3.0-0.rc3.git1.1 (commit 33920f1ec5bf - works fine)
> >> and 5.3.0-0.rc4.git0.1 (tag v5.3-rc4 - fails with errors).
> >>
> >> It's just a few days (7-11 Aug) and "only" around 250 commits. I went
> >> through them, but (based on the commits name) I haven't seen any nouveau
> >> related changes and in general no very suspected drm related changes.
> >>
> >>> git log 33920f1ec5bf..v5.3-rc4 --stat
> >>
> >>
> >> Maybe some of more nouveau/drm-experienced developers could take a look
> >> at that to determine which commit could break it (to make it easier to
> >> find out what should be fixed to prevent that regression)?
> >>
> >>
> >> [1] -
> >> https://gitlab.freedesktop.org/xorg/driver/xf86-video-nouveau/issues/516
> >>
> >> Thanks in advance
> >> Marcin
> >> _______________________________________________
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