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

[Christian Kastner]

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?

Regards,
Christian


PS: Please CC: me as I am not subscribed to this list.