Intel drm random freezes with Z36xxx/Z37xxx and several current 4.x kernels?

[Bruno Kant]

Hello,

According to what I read, video related bug reports could be feed to 
xorg developpers, they would care about the kernel driver also.

Is this an adequate list for such reports? Would you have an easy way to 
get a diff for Intel Z36xxx/Z37xxx driver, between those two Fedora 
kernel builds?

- 4.5.0-0.rc2.git0.1.vanilla.knurd.1.fc23
- 4.5.0-0.rc2.git1.1.vanilla.knurd.1.fc23

As further described below, git0.1 is stable with my XS35V4 Shuttle. But 
git1.1 often freezes, like some other current kernels dnf installed by 
fc23.

This Shuttle XS35V4 is new, came with the latest XS35V400.400 BIOS 
installed. I now have a Win10/Fedora 23 dual boot installed on it. Win 
10 is stable, I could watch videos with Win 10 during hours. Running 
Linux is a different story.

 From the standard Shuttle XS35V4 hardware, a barbone:

# lspci -nnk | egrep -iA3 "VGA"
00:02.0 VGA compatible controller [0300]: Intel Corporation Atom 
Processor Z36xxx/Z37xxx Series Graphics & Display [8086:0f31] (rev 0e)
         DeviceName:  Onboard IGD
         Subsystem: Holco Enterprise Co, Ltd/Shuttle Computer Device 
[1297:4019]
         Kernel driver in use: i915

With current Fedora 23 kernels, my XS35V4 freezes randomly as soon I'm 
using X. It frozed also several times during Fedora Workstation 
installation (a GUI). I had to reboot/restart the install to get Fedora 
23 on it. Then I noticed fc23 Xorg freezes after 30 to 40 minutes uptime 
with load. fc23 Xorg freezed also with no load, takes some more time. 
fc23 ran stable with gdm/Xorg disabled.

Googling around, I found a way to disable Intel DRI/accelleration. My X 
environnement was stable for hours with heavy load and those next lines 
added to the box and current 4.3.3 or 4.3.4 fc23 kernels:

# cat /etc/X11/xorg.conf.d/20-intel.conf
Section "Device"
         Identifier      "Intel Graphics"
         Driver          "intel"
         Option          "NoAccel" "True"
         Option          "DRI" "False"
EndSection

I found also that the Intel driver itself was improved over months. 
Current Fedora 23 4.3 kernels seem to be build around 
xorg-x11-drv-intel/2.99.917/16.20150729.fc23, which is of last jully.

Digging more in sources, I read:
- kernel 4.3 is based on 20150731 (unstable for that Shuttle)
- kernel 4.4 is based on 20151010 (not tested)
- kernel 4.5-rc2 (precise git0.1 build) is based on 20151218 (tests 
ongoing, this Shuttle and kernel seem to be much more stable, the uptime 
reaches hours)

Top of Fedora 23, I installed x86_64 
4.5.0-0.rc2.git0.1.vanilla.knurd.1.fc23 from their vanilla-mainline 
repo. This was stable for hours, with accel and DRI active and with a 
heavy load for this Celeron (3 video streams plus one VM running in 
QEMU/KVM).

Then I choosed to reinstall fc23 from scratch. And vanilla-mainline repo 
added kernel version git1.1 (the update) during my latest reinstall. 
Then my Shuttle started to quickly freeze again.

I now forced 4.5.0-0.rc2.git0.1.vanilla.knurd.1.fc23 kernel reinstall on 
my fc23/XS35V4 box and it seems much stable again, which is why I 
suggest you to catch this Fedora 23 git0.1/git1.1 Intel driver diff.

Best regards