[Bug 207889] Significant increase in Sandy Bridge laptop power consumption after Linux 3.8 i915 update

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Mon Mar 21 01:23:30 UTC 2016


https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=207889

--- Comment #3 from Ed Maste <emaste at freebsd.org> ---
(In reply to Jan Bramkamp from comment #1)

I tried with enable_rc6 set to 0, 1, and 7.

One other note: When I observed excessive power consumption the "residency
since boot" counters were static in "sysctl hw.dri.0.info.i915_drpc_info"
output. "RC6 residency since boot" was high and unchanging, while the other two
were zero. This is similar to a report in a comment in
https://bugs.freedesktop.org/show_bug.cgi?id=54089

The Linux commit that introduced this regression is
b4ae3f22d238617ca11610b29fde16cf8c0bc6e0, which was in response to
https://bugs.freedesktop.org/show_bug.cgi?id=50237 .  Disabling the MBCTL write
from that commit, on Sandy Bridge, restores the power consumption to normal.

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