[coreboot-gerrit] Patch merged into coreboot/master: vboot: Clear battery cutoff flags when vbnv_cmos loads backup VBNV.

the following patch was just integrated into master:
commit fe2fc8393632c90b17b9415bdc496d9c38b1f156
Author: Hung-Te Lin 
Date:   Thu Dec 29 20:59:37 2016 +0800

vboot: Clear battery cutoff flags when vbnv_cmos loads backup VBNV.

When CONFIG_VBOOT_VBNV_CMOS_BACKUP_TO_FLASH is set, vbnv_cmos will try
    to load VBNV from flash if the VBNV in CMOS is invalid. This is usually
    correct, except the case of battery cut-off.

CMOS will always be invalid after battery cut-off if there is no RTC
    battery (or if that is dead). However, in current implementation the
    backup in flash is only updated in coreboot, while the real battery
    cutoff (and the clearing of cutoff flags in VBNV) is done in payload
    (Depthcharge) stage. This will create an endless reboot loop that:

1. crossystem sets battery cutoff flag in VBNV_CMOS then reboot.
     2. coreboot backs-up VBNV_CMOS to VBNV_flash.
     3. Depthcharge sees cutoff flag in VBNV_CMOS.
     4. Depthcharge clears cutoff flag in VBNV_CMOS.
     5. Depthcharge performs battery cutoff (CMOS data is lost).
     6. (Plug AC adapter) Reboot.
     7. Coreboot sees invalid VBNV_CMOS, load backup from VBNV_flash.
     8. Jump to 3.

As a result, we should always clear battery cutoff flags when loading
    backups from VBNV_flash.

BRANCH=glados,reef
    BUG=chrome-os-partner:61365,chrome-os-partner:59615
    TEST=emerge-reef coreboot bootimage;

Change-Id: I3250a3a179a7b0de9c6e401e4a94dcd23920e473
    Signed-off-by: Hung-Te Lin 
    Reviewed-on: https://chromium-review.googlesource.com/423460
    Reviewed-by: Duncan Laurie 
    Reviewed-on: https://review.coreboot.org/18008
    Reviewed-by: Paul Menzel 
    Tested-by: build bot (Jenkins)
    Reviewed-by: Martin Roth

See https://review.coreboot.org/18008 for details.

-gerrit