Created attachment 116084 [details]
dmesg captured with kdump

Hi,

My Lenovo W540 started crashing when I upgraded from Linux 3.14 to 3.16 in Sept
2014. I continued to use 3.14 and I did nothing till last week when I tried
Linux 4.0 (from sid) which kept crashing soon after logging in to GNOME 3. I
EFI boot to grub and use GRUB_GFXPAYLOAD_LINUX=keep. Then use KMS and Plymouth
till GDM, X.Org and GNOME3. When it crashed the mouse and keyboard no longer
did anything (ie Ctrl-Alt-F1 did not work) and the laptop appeared to drop off
the network. 

When I boot with Linux 4.0 and login to GNOME 3, it would crash within minutes,
but sometimes an hour. I manually compiled 3.15, 3.16, 3.17, 3.18, 3.19 and 4.0
which all had various issues: the external monitor resolution was broken on
3.15, 3.16 seemed ok, but 3.17, 3.18, 3.19 and 4.0 all seemed to crash soon
after boot.

I used kdump to capture a dump and dmesg and there was a message about nouveau:
[   76.792370] nouveau E[     DRM] failed to idle channel 0xcccc0001 [DRM]

Then 60 microseconds later a BUG:
[   76.792430] BUG: unable to handle kernel paging request at ffff8805660b7ffc
[   76.792455] IP: [<ffffffffa0406bf3>] evo_wait+0x53/0x120 [nouveau]

After a little googling I found out about the "nouveau.runpm=0" parameter. Once
I added this parameter and rebooted my laptop has worked fine with Linux 4.0.
However I have not tried that parameter in any previous kernels so am unsure
which release this workaround started working.

I'm now happy that I have a working system with working lcd screen brightness
controls and multi-stream transport monitors that work. However I don't want to
kill the laptops battery by permanently disabling the power management. I could
try bisecting, but with so many revisions I'm not sure what to mark good and
bad or if I should use runpm at all.

Anyway here are some Debian package versions and info:
linux-image-4.0.0-1-amd64       4.0.2-1
libdrm-nouveau2                 2.4.60-3
libgl1-mesa-glx                 10.5.5-1
xserver-xorg-video-nouveau      1:1.0.11-1+b1

$ lspci | grep -i VGA
00:02.0 VGA compatible controller: Intel Corporation 4th Gen Core Processor
Integrated Graphics Controller (rev 06)
01:00.0 VGA compatible controller: NVIDIA Corporation GK106GLM [Quadro K2100M]
(rev a1)
$

Kind Regards
--
Tom