[Intel-gfx] Macbook Air 6, 2: i915-related interrupt storm after Yosemite update

[Daniel Vetter]

On Sat, Nov 01, 2014 at 06:08:00PM +0100, Christian Kastner wrote:
> Hi,
> 
> I have a Macbook Air (2013) (6,2) which until recently was working
> flawlessly with Debian unstable, which I use almost exclusively on that
> machine. I did keep the OSX installation, mainly because it's the only
> way to get firmware updates.
> 
> Recently, in a moment of weakness, I said "yes" to the offer of
> upgrading OSX to Yosemite. Since then, whenever I boot Debian, there is
> an i915-related interrupt storm, with a kworker thread constantly
> running at 70%.
> 
> Downgrading OSX back to Mavericks did not help. Apparently Yosemite
> included firmware updates, as within OSX I am shown version numbers that
> are so new they aren't even listed on Apple's homepage yet.
> 
> Here's what I see:
> 
>   $ GPE=/sys/firmware/acpi/interrupts/gpe66
>   $ while true; doe cat $GPE; sleep 1; done
>   727268   enabled
>   757981   enabled
>   788576   enabled
>   807337   enabled
>   828426   enabled
>         ...
> 
> I've tested this with 3.16 and 3.17 kernels; I was using the former for
> about a month now without issue.
> 
> When I boot with modprobe.blacklist=i915, the issue disappears.
> 
> Does anyone have an idea what could be going on?

The only acpi interrupt we're handling is asle afaik, so sounds like
something we do in there doesn't please the new firmware and sends it into
a tailspin. So I'd sprinkle printks all over the place there until you
know what exactly goes on in i915, starting with the asle functions.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch