cheza: Add board reset via Chrome EC

This patch implements board reset on the Cheza board. The real board
reset used by the operating system uses the PMIC, but unfortunately the
PMIC needs to be configured right for that to work. The PMIC
configuration currently happens in the Qualcomm blob (QcLib) that is run
from romstage, but vboot needs to be able to reboot during verstage
already. Porting all the PMIC initialization code to run in the
bootblock seems excessive (and at odds with the goal of doing as little
as possible before verification), so we'll just do a little hack and ask
the EC to perform a cold reset instead. For vboot purposes, this should
work just as well.

BUG=b:118501305
TEST=Hacked vboot code to call vboot_reboot(), confirmed that board
reset and came back up as expected.

Change-Id: I3858d95f481884a87c243d4fa3d6369c1e8a5a2c
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://review.coreboot.org/c/29849
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/cheza/Kconfig

@@ -16,7 +16,6 @@ config BOARD_SPECIFIC_OPTIONS
 	select SPI_FLASH
 	select SPI_FLASH_WINBOND
 	select MAINBOARD_HAS_CHROMEOS
-	select MISSING_BOARD_RESET
 	select MAINBOARD_HAS_TPM2
 	select MAINBOARD_HAS_SPI_TPM_CR50
 

src/mainboard/google/cheza/Makefile.inc

@@ -17,17 +17,21 @@ bootblock-y += boardid.c
 bootblock-y += memlayout.ld
 bootblock-y += chromeos.c
 bootblock-y += bootblock.c
+bootblock-y += reset.c
 
 verstage-y += boardid.c
 verstage-y += memlayout.ld
 verstage-y += chromeos.c
+verstage-y += reset.c
 
 romstage-y += boardid.c
 romstage-y += memlayout.ld
 romstage-y += chromeos.c
 romstage-y += romstage.c
+romstage-y += reset.c
 
 ramstage-y += boardid.c
 ramstage-y += memlayout.ld
 ramstage-y += chromeos.c
 ramstage-y += mainboard.c
+ramstage-y += reset.c

src/mainboard/google/cheza/reset.c

@@ -0,0 +1,24 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright 2018 Google LLC
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <ec/google/chromeec/ec.h>
+#include <reset.h>
+
+/* Can't do a "real" reset before the PMIC is initialized in QcLib (romstage),
+   but this works well enough for our purposes. */
+void do_board_reset(void)
+{
+	google_chromeec_reboot(0, EC_REBOOT_COLD, 0);
+}