[coreboot-gerrit] Patch merged into coreboot/master: lenovo/x200, t400: enable C4 cpu low power state

[gerrit at coreboot.org]

the following patch was just integrated into master:
commit 2a1847ea125b4b867f435635173acb39c9d75292
Author: Arthur Heymans <arthur at aheymans.xyz>
Date:   Fri Jun 17 19:06:25 2016 +0200

    lenovo/x200,t400: enable C4 cpu low power state
    
    This enables the C4 low power state on the lenovo x200 and t400.
    It's inspired by the thread on the mailinglist:
    "[coreboot] Lenovo X200 running Coreboot drains 3-4W more power
    than with Vendor BIOS".
    
    What this does, is to enable a C3 state using MWAIT(C3) request
    and set the southbridge config c4onc3_enable to automatically
    upgrade C3 to the lower power C4 state.
    The latency (0x37) is the same value used by the vendor bios.
    
    With C4 enabled the idle power consumption is about ~2-3W lower.
    
    TEST= build and install on target. Use powertop top to measure power
    usage. To manually disable c-state to compare them,
    do (tested on linux 4.4):
    echo 1 > /sys/devices/system/cpu/cpu*/cpuidle/stateX/disable
    
    Change-Id: I1a1663a7662ebc7157a965667680688ad6a33545
    Signed-off-by: Arthur Heymans <arthur at aheymans.xyz>
    Reviewed-on: https://review.coreboot.org/15251
    Tested-by: build bot (Jenkins)
    Reviewed-by: Swift Geek
    Reviewed-by: Paul Menzel <paulepanter at users.sourceforge.net>
    Reviewed-by: Nico Huber <nico.h at gmx.de>


See https://review.coreboot.org/15251 for details.

-gerrit