[Bug 54226] [snb 3.5] stale semaphore sync seqno (typically as seen on bcs->rcs)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=54226

--- Comment #227 from Martin Steigerwald <Martin at Lichtvoll.de> ---
(In reply to Chris Wilson from comment #226)
> (In reply to Martin Steigerwald from comment #225)
> > Chris, you referred me to this bug as I reported
> > 
> > Bug 90835 - [4.1-rc6] gpu hang: ecode 6:-1:0x00000000, Kicking stuck
> > semaphore on render ring
> > 
> > I skimmed through it and it appears that there are some patches to test? But
> > I am not sure which ones these are. Can you or someone else enlighten me?
> 
> There's likely a modest improvement in 4.2.

Nice.

> > Also I note that I still use
> > 
> >         Option          "AccelMethod"   "uxa"
> > 
> > and I have
> > 
> > martin at merkaba:~> cat /etc/modprobe.d/i915-kms.conf 
> > options i915 modeset=1 i915_enable_rc6=7
> 
> Fortuitously that dangerous option doesn't do anything for your kernel.

Well I found out why, I compiled i915 into the kernel it seems, at least I
don´t have an i915 module in lsmod. But also i915.i915_enable_rc6=7 on kernel
command line does not seem to have any effect. I removed the option.

> > ffffffff813a4b0e
> > thus maximum energy saving. But according to powertop it never enters the
> > highest sleep state anyway.
> > 
> > I will remove the AccelMethod setting now and see whether it helps. If not,
> > I downgrade to 4.1-rc4 for now, as issues have been at least much less
> > frequent with it.
> 
> Purely circumstantial.

Since using SNA I didn´t see a GPU hang so far. Too early to say for sure, but
it seems something in UXA may have triggered it more easily.

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