pit: Drop EC clock speed to 1 MHz MSI when AP is in S3/S5

Automatically drop the clock speed to 1 MHz MSI, then disable HSI and
move to lower-power flash mode.  This cuts power from 2400uA to 150uA.

Note that at 1 MHz, we drop received characters on the UART if you
type too fast (or copy/paste, or use arrow keys).  Clock speed can be
manually overridden back to 16 MHz via 'clock hsi'.

BUG=chrome-os-partner:20414
BRANCH=none
TEST=with AP on, 'clock' reports 16 MHz.
     with AP off, 'clock' reports 1 MHz.

Change-Id: I070c80db0aa5f3a98a7bad6050890bcc2fe008d6
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/59832

0 files changed, 0 insertions, 0 deletions