This adds the very basic top-level support for determining the
system wake source from ACPI. It only implements the _SWS method
in the _SB scope which just returns a bit index into the PM1
status register for the first fixed functional block.
This can be used to determine wake source of RTC or Power Button
but does not help determine wake source for USB or GPIO.
The ACPI spec says to return -1 if no source can be determined
from PM1 status register.
BUG=chrome-os-partner:8127
BRANCH=baytrail
TEST=build and boot on rambi
1) Test resume from S3 by RTC:
ACPI System Wake Source is PM1 Index 10
(bit 10 is RTC_STS in ACPI spec, ACPI_EVENT_RTC in kernel)
2) Test resume from S3 by power button:
ACPI System Wake Source is PM1 Index 8
(bit 8 is PWRBTN_STS in ACPI spec, ACPI_EVENT_POWER_BUTTON in kernel)
3) Test resume from S3 by USB:
ACPI System Wake Source is PM1 Index -1
Change-Id: Ifc5c0867f82cf291af157537b8c13fe44923d8f5
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/183333
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
a6b85ad950