[Bug 88012] [bisected BYT] complete freeze after: drm/i915/vlv: WA for Turbo and RC6 to work together

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=88012

Juha Sievi-Korte <jsievikorte at gmail.com> changed:

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--- Comment #116 from Juha Sievi-Korte <jsievikorte at gmail.com> ---
Hi All,

Came across this when hunting random freezes / crashes on Acer B115 laptop. It
started with upgrade to ubuntu 15.04 (14.x worked ok, haven't noted the kernel
versions).

http://ubuntuforums.org/showthread.php?t=2284615&p=13313066#post13313066 My
original post in here.

OpenSuSE with kernel 4.0.5 seemed to run fine, but it might be that I looked it
at the wrong end, because 15.04 ubuntu crashed only when going to sleep so that
is the thing I tried to track down. 15.10 now crashes randomly during desktop
use - and same happens in OpenSuSE Tumbleweed with 4.3 kernel.

Crashes seem intermittent, might make days without freeze and then couple of
nights back two freezes in a row, second one just couple of minutes after
reboot. Only load was chromium showing couple of large web pages when crashes
happened. Symptons are quite same described in many posts, no sysrq possible,
only power off works.

I did already try intel_pstate=disable and that made the system freeze on
screensaver after just few minutes of uptime. After that I've booted with
debugging options enabled and fiddled a bit with clock frequency setting, and
haven't managed to crash since - but I'm still only three days up. Tried to
make it crash by playing couple of games and/or HD videos, no luck so far. But
this is to be expected, 15.10 ubuntu could also run couple of weeks - which
makes this painful as there seems to be no clear way of reproducing the issue.

Just it makes me think that is there something going on with timings at
hardware level? What I did try was to lower the frequency setting just lightly,
with quick testing it didn't seem to matter how much I touched it. Also I'm a
bit puzzled about the setting, is the /sys/kernel/debug/dri/0/i915_max_freq
value in MHz or something else, as in log it says: 

[26873.155419] [drm:valleyview_enable_rps] current GPU freq: 312 MHz (198)
[26873.155420] [drm:valleyview_enable_rps] setting GPU freq to 645 MHz (214)

And I think I saw this high values in log, even if I did set the frequency
value to less than 400. Anyway, I'll update if I found anything else, this is
annoying as it has been going on months now without a clear clue what is wrong
with this laptop :)

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