[Bug 578673] Re: [arrandale] Resume doesn't work on a Latitude E6410

[mikeos]

I think I identified the problem on my system Dell Latitude E6410 with Intel i7 CPU.
Disabling Intel SpeedStep feature in BIOS does the trick. Battery life decrease seems insignificant thanks to power management assured by CPU C-states.  What's interesting that the CPU multiplier is still variable (according to i7z) even with SpeedStep disabled, though the very low frequencies and turbo-boost frequency are never reached in contrast with SpeedStep enabled setup with ondemand governor. 

Successfully tested on 20 consecutive suspend/resume cycles on battery,
same on AC power.

Why does resume with SpeedStep enabled *only* fail when the machine is
running on battery power remains unknown. Before forcibly disabling
SpeedStep in BIOS I did a lot of different tests, disabling any possible
PM scripts which either modified CPU governors (as e.g. /usr/lib/pm-
utils/sleep.d/94cpufreq seems to do) or report the power state to other
scripts (like /usr/lib/pm-utils/functions) forcing it to report that the
machine is on AC-power even though it was not. Nothing was reliable
enough.

Is it a BIOS bug? Someone with Dell Latitude e6410, BIOS rev.A05, Intel
i7  M 620 at 2.67GHz  can report the resume behavior when running on
batteries with SpeedStep enabled? Both variants with either nVidia or
Intel  GFX  should suffer from the same problem (if my laptop is not
unique...)

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[arrandale] Resume doesn't work on a Latitude E6410
https://bugs.launchpad.net/bugs/578673
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