[Intel-gfx] kernel panic on intel gen4 gfx card

[? ?]

Hi, Greg

I found on Debian testing with kernel 4.18.20 fail boot, kernel panic
on i915. and reported it to Debian bug 917280 [0], with panic log[1].

after revert:

commit 06e562e7f515292ea7721475950f23554214adde
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Nov 5 09:43:05 2018 +0000

    drm/i915/ringbuffer: Delay after EMIT_INVALIDATE for gen4/gen5

System boots to desktop.

[0]: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=917280
[1]:
https://bugs.debian.org/cgi-bin/bugreport.cgi?att=1;bug=917280;filename=dmesg.txt;msg=10

BR.
Ning.