intel/skylake: implement vboot_platform_is_resuming()

To allow skylake platforms to run with verified memory init
code the chipset needs to implement vboot_platform_is_resuming()
so that the vboot code can make proper decisions.

BUG=chrome-os-partner:46049
BRANCH=glados
TEST=Suspended and resumed on chell. Also, tested with an EC build
     which returns a bad hash to ensure that is properly caught.

Change-Id: I508a339c07dcc9e7c56a0df4201660827b3ae07a
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: a3e11789339bcd8fc8fc99b704c6a1110acf5302
Original-Change-Id: I40264019eb28e85795258112c720056a6a3fc523
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/323503
Original-Reviewed-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://review.coreboot.org/13578
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/soc/intel/skylake/romstage/Makefile.inc

@@ -1,5 +1,6 @@
 verstage-y += cpu.c
 verstage-y += pch.c
+verstage-y += power_state.c
 verstage-y += report_platform.c
 verstage-y += romstage.c
 verstage-y += smbus.c

src/soc/intel/skylake/romstage/power_state.c

@@ -30,6 +30,7 @@
 #include <soc/pci_devs.h>
 #include <soc/pm.h>
 #include <soc/romstage.h>
+#include <vendorcode/google/chromeos/vboot_common.h>
 
 static struct chipset_power_state power_state CAR_GLOBAL;
 
@@ -151,3 +152,9 @@ struct chipset_power_state *fill_power_state(void)
 
 	return ps;
 }
+
+int vboot_platform_is_resuming(void)
+{
+	int typ = (inl(ACPI_BASE_ADDRESS + PM1_CNT) & SLP_TYP) >> SLP_TYP_SHIFT;
+	return typ == SLP_TYP_S3;
+}