[Trusty Patch] intel_pstate: Add setting voltage value for baytrail P states

[Yingying Zhao]

There's a bug that kernel fails to boot with intel_pstate enabled on BayTrail-M which said: Problem only occurs on 4 core Pentium CPU. It appears to be a race condition in the kernel that only happens when intel_pstate sets the processor to run at it's highest speed early in the boot process, so not a intel_pstate problem per se, just exposed by intel_pstate.

This bug is fixed by this patch which is queued for 3.14-rc1 and market for 3.13 stable.
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/commit/?id=007bea098b869945a462420a1f9d442ff169f722

intel_pstate: Add setting voltage value for baytrail P states.
Baytrail requires setting P state and voltage pairs when adjusting the
requested P state. Add function for retrieving the valid voltage
values and modify *_set_pstate() functions to caluclate the
appropriate voltage for the requested P state.

Signed-off-by: Dirk Brandewie <email address hidden>
Signed-off-by: Rafael J. Wysocki <email address hidden>

Please consider to include this patch in Trusty.

[Tim Gardner (timg-tpi)]

Ubuntu-3.13.0-5.20