[POWERPC] Add restart support for mpc52xx based platforms

Add common helper routines: mpc52xx_map_wdt() and mpc52xx_restart().
Signed-off-by: Marian Balakowicz <m8@semihalf.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/powerpc/platforms/52xx/mpc52xx_common.c

@@ -18,6 +18,13 @@
 #include <asm/prom.h>
 #include <asm/mpc52xx.h>
 
+/*
+ * This variable is mapped in mpc52xx_map_wdt() and used in mpc52xx_restart().
+ * Permanent mapping is required because mpc52xx_restart() can be called
+ * from interrupt context while node mapping (which calls ioremap())
+ * cannot be used at such point.
+ */
+static volatile struct mpc52xx_gpt *mpc52xx_wdt = NULL;
 
 static void __iomem *
 mpc52xx_map_node(struct device_node *ofn)
@@ -126,3 +133,46 @@ mpc52xx_declare_of_platform_devices(void)
 			"Error while probing of_platform bus\n");
 }
 
+void __init
+mpc52xx_map_wdt(void)
+{
+	const void *has_wdt;
+	struct device_node *np;
+
+	/* mpc52xx_wdt is mapped here and used in mpc52xx_restart,
+	 * possibly from a interrupt context. wdt is only implement
+	 * on a gpt0, so check has-wdt property before mapping.
+	 */
+	for_each_compatible_node(np, NULL, "fsl,mpc5200-gpt") {
+		has_wdt = of_get_property(np, "fsl,has-wdt", NULL);
+		if (has_wdt) {
+			mpc52xx_wdt = mpc52xx_map_node(np);
+			return;
+		}
+	}
+	for_each_compatible_node(np, NULL, "mpc5200-gpt") {
+		has_wdt = of_get_property(np, "has-wdt", NULL);
+		if (has_wdt) {
+			mpc52xx_wdt = mpc52xx_map_node(np);
+			return;
+		}
+	}
+}
+
+void
+mpc52xx_restart(char *cmd)
+{
+	local_irq_disable();
+
+	/* Turn on the watchdog and wait for it to expire.
+	 * It effectively does a reset. */
+	if (mpc52xx_wdt) {
+		out_be32(&mpc52xx_wdt->mode, 0x00000000);
+		out_be32(&mpc52xx_wdt->count, 0x000000ff);
+		out_be32(&mpc52xx_wdt->mode, 0x00009004);
+	} else
+		printk("mpc52xx_restart: Can't access wdt. "
+			"Restart impossible, system halted.\n");
+
+	while (1);
+}

include/asm-powerpc/mpc52xx.h

@@ -259,6 +259,9 @@ extern unsigned int mpc52xx_get_irq(void);
 
 extern int __init mpc52xx_add_bridge(struct device_node *node);
 
+extern void __init mpc52xx_map_wdt(void);
+extern void mpc52xx_restart(char *cmd);
+
 #endif /* __ASSEMBLY__ */
 
 #ifdef CONFIG_PM