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

[Marcin Zajączkowski]

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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