mec1322: Add watchdog support

This implements the basic watchdog support. For now, the watchdog
doesn't warn us before it expires. This functionality will be added
later using a basic timer.

BUG=chrome-os-partner:24107
TEST='waitms 700' and the EC stays alive.
TEST='waitms 1200' and the EC reboots.
BRANCH=None

Change-Id: I1cc48978ed09577ae88cc2f7a6087867e5854973
Signed-off-by: Vic (Chun-Ju) Yang <victoryang@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/177736

board/mec1322_evb/board.h

@@ -19,7 +19,6 @@
 #undef CONFIG_LPC
 #undef CONFIG_PECI
 #undef CONFIG_SWITCH
-#undef CONFIG_WATCHDOG
 
 #ifndef __ASSEMBLER__
 

chip/mec1322/build.mk

@@ -13,3 +13,4 @@ CFLAGS_CPU+=-march=armv7e-m -mcpu=cortex-m4
 
 # Required chip modules
 chip-y=clock.o gpio.o hwtimer.o system.o uart.o jtag.o
+chip-$(CONFIG_WATCHDOG)+=watchdog.o

chip/mec1322/watchdog.c

@@ -0,0 +1,32 @@
+/* Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Watchdog driver */
+
+/*
+ * TODO(crosbug.com/p/24107): Use independent timer for warning before watchdog
+ *                            timer expires.
+ */
+
+#include "hooks.h"
+#include "registers.h"
+#include "watchdog.h"
+
+void watchdog_reload(void)
+{
+	MEC1322_WDG_KICK = 1;
+}
+DECLARE_HOOK(HOOK_TICK, watchdog_reload, HOOK_PRIO_DEFAULT);
+
+int watchdog_init(void)
+{
+	/* Set timeout. It takes 1007us to decrement WDG_CNT by 1. */
+	MEC1322_WDG_LOAD = WATCHDOG_PERIOD_MS * 1000 / 1007;
+
+	/* Start watchdog */
+	MEC1322_WDG_CTL |= 1;
+
+	return EC_SUCCESS;
+}