ARM: sun6i: Add restart code for the A31

The Allwinner A31 has a different watchdog, with a slightly different
register layout, that requires a different restart code.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/watchdog/sun4i-wdt.txt → Documentation/devicetree/bindings/watchdog/sunxi-wdt.txt

-Allwinner sun4i Watchdog timer
+Allwinner SoCs Watchdog timer
 
 Required properties:
 
-- compatible : should be "allwinner,sun4i-wdt"
+- compatible : should be "allwinner,<soc-family>-wdt", the currently supported
+  SoC families being sun4i and sun6i
 - reg : Specifies base physical address and size of the registers.
 
 Example:

arch/arm/mach-sunxi/sunxi.c

@@ -27,10 +27,19 @@
 #include <asm/system_misc.h>
 
 #define SUN4I_WATCHDOG_CTRL_REG		0x00
-#define SUN4I_WATCHDOG_CTRL_RESTART		(1 << 0)
+#define SUN4I_WATCHDOG_CTRL_RESTART		BIT(0)
 #define SUN4I_WATCHDOG_MODE_REG		0x04
-#define SUN4I_WATCHDOG_MODE_ENABLE		(1 << 0)
-#define SUN4I_WATCHDOG_MODE_RESET_ENABLE	(1 << 1)
+#define SUN4I_WATCHDOG_MODE_ENABLE		BIT(0)
+#define SUN4I_WATCHDOG_MODE_RESET_ENABLE	BIT(1)
+
+#define SUN6I_WATCHDOG1_IRQ_REG		0x00
+#define SUN6I_WATCHDOG1_CTRL_REG	0x10
+#define SUN6I_WATCHDOG1_CTRL_RESTART		BIT(0)
+#define SUN6I_WATCHDOG1_CONFIG_REG	0x14
+#define SUN6I_WATCHDOG1_CONFIG_RESTART		BIT(0)
+#define SUN6I_WATCHDOG1_CONFIG_IRQ		BIT(1)
+#define SUN6I_WATCHDOG1_MODE_REG	0x18
+#define SUN6I_WATCHDOG1_MODE_ENABLE		BIT(0)
 
 static void __iomem *wdt_base;
 
@@ -56,8 +65,36 @@ static void sun4i_restart(enum reboot_mode mode, const char *cmd)
 	}
 }
 
+static void sun6i_restart(enum reboot_mode mode, const char *cmd)
+{
+	if (!wdt_base)
+		return;
+
+	/* Disable interrupts */
+	writel(0, wdt_base + SUN6I_WATCHDOG1_IRQ_REG);
+
+	/* We want to disable the IRQ and just reset the whole system */
+	writel(SUN6I_WATCHDOG1_CONFIG_RESTART,
+		wdt_base + SUN6I_WATCHDOG1_CONFIG_REG);
+
+	/* Enable timer. The default and lowest interval value is 0.5s */
+	writel(SUN6I_WATCHDOG1_MODE_ENABLE,
+		wdt_base + SUN6I_WATCHDOG1_MODE_REG);
+
+	/* Restart the watchdog. */
+	writel(SUN6I_WATCHDOG1_CTRL_RESTART,
+		wdt_base + SUN6I_WATCHDOG1_CTRL_REG);
+
+	while (1) {
+		mdelay(5);
+		writel(SUN6I_WATCHDOG1_MODE_ENABLE,
+			wdt_base + SUN6I_WATCHDOG1_MODE_REG);
+	}
+}
+
 static struct of_device_id sunxi_restart_ids[] = {
 	{ .compatible = "allwinner,sun4i-wdt", .data = sun4i_restart },
+	{ .compatible = "allwinner,sun6i-wdt", .data = sun6i_restart },
 	{ /*sentinel*/ }
 };