ARM: sunxi: Add sunxi restart function via onchip watchdog

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/watchdog/sunxi-wdt.txt

+Allwinner sunXi Watchdog timer
+
+Required properties:
+
+- compatible : should be "allwinner,sunxi-wdt"
+- reg : Specifies base physical address and size of the registers.
+
+Example:
+
+wdt: watchdog@01c20c90 {
+	compatible = "allwinner,sunxi-wdt";
+	reg = <0x01c20c90 0x10>;
+};

arch/arm/boot/dts/sunxi.dtsi

@@ -42,11 +42,16 @@ soc {
 
 		timer@01c20c00 {
 			compatible = "allwinner,sunxi-timer";
-			reg = <0x01c20c00 0x400>;
+			reg = <0x01c20c00 0x90>;
 			interrupts = <22>;
 			clocks = <&osc>;
 		};
 
+		wdt: watchdog@01c20c90 {
+			compatible = "allwinner,sunxi-wdt";
+			reg = <0x01c20c90 0x10>;
+		};
+
 		intc: interrupt-controller@01c20400 {
 			compatible = "allwinner,sunxi-ic";
 			reg = <0x01c20400 0x400>;

arch/arm/mach-sunxi/sunxi.c

@@ -12,6 +12,7 @@
 
 #include <linux/kernel.h>
 #include <linux/init.h>
+#include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/io.h>
@@ -26,6 +27,36 @@
 
 #include "sunxi.h"
 
+#define WATCHDOG_CTRL_REG	0x00
+#define WATCHDOG_MODE_REG	0x04
+
+static void __iomem *wdt_base;
+
+static void sunxi_setup_restart(void)
+{
+	struct device_node *np = of_find_compatible_node(NULL, NULL,
+						"allwinner,sunxi-wdt");
+	if (WARN(!np, "unable to setup watchdog restart"))
+		return;
+
+	wdt_base = of_iomap(np, 0);
+	WARN(!wdt_base, "failed to map watchdog base address");
+}
+
+static void sunxi_restart(char mode, const char *cmd)
+{
+	if (!wdt_base)
+		return;
+
+	/* Enable timer and set reset bit in the watchdog */
+	writel(3, wdt_base + WATCHDOG_MODE_REG);
+	writel(0xa57 << 1 | 1, wdt_base + WATCHDOG_CTRL_REG);
+	while(1) {
+		mdelay(5);
+		writel(3, wdt_base + WATCHDOG_MODE_REG);
+	}
+}
+
 static struct map_desc sunxi_io_desc[] __initdata = {
 	{
 		.virtual	= (unsigned long) SUNXI_REGS_VIRT_BASE,
@@ -42,6 +73,8 @@ void __init sunxi_map_io(void)
 
 static void __init sunxi_dt_init(void)
 {
+	sunxi_setup_restart();
+
 	of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL);
 }
 
@@ -56,6 +89,7 @@ DT_MACHINE_START(SUNXI_DT, "Allwinner A1X (Device Tree)")
 	.map_io		= sunxi_map_io,
 	.init_irq	= sunxi_init_irq,
 	.handle_irq	= sunxi_handle_irq,
+	.restart	= sunxi_restart,
 	.timer		= &sunxi_timer,
 	.dt_compat	= sunxi_board_dt_compat,
 MACHINE_END