Sandy Bridge: Return of the "running fan" issue

[Johannes Bauer <dfnsonfsduifb@gmx.de>]

Dear list,

I've previously had an issue with my Dell Laptop (Latitude E5520) which
has a i915 graphics card on a Sandy Bridge (2011-12-13 "Fan running with
Intel Graphics"). The fan was running because apparently the GPU was not
going into powersave mode.

Now, by sheer stupidity on my part, I've lost my kernel configuration
and the (working) kernel image. So I embarked on the journey to retrieve
the latest git and see how it goes. Sadly, the running fan is back: I've
checked out drm-intel-testing, rev. c3c3d4e9.

My kernel command line looks like this:
pcie_aspm=force i915.i915_enable_rc6=3 i915.lvds_downclock=1
i915.i915_enable_fbc=1 nomodeset

Previously, I've always done

echo 400 >/sys/kernel/debug/dri/0/i915_max_freq

but with this kernel revision, /sys/kernel/debug/dri/ is empty and
there's no i915_max_freq node anywhere to be found within /sys.

Should I update to a different branch? Should I change the kernel
command line? Or are there other options?

Any advice is greatly appreciated,
All the best,
Joe