power: reset: driver for the Versatile syscon reboot

This driver enabled us to drive the reboot of the Versatile family
of ARM reference boards. Even though only the RealView boards are
supported initially, these boards all have the same procedure for
reboot:

- Write a magic value into an unlocking register
- Write another magic value into a reset control register

The driver will be reusable for Versatile and possibly also the
Integrator family of reference boards.

Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Acked-By: Sebastian Reichel <sre@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

drivers/power/reset/Kconfig

@@ -92,6 +92,15 @@ config POWER_RESET_SUN6I
 	help
 	  Reboot support for the Allwinner A31 SoCs.
 
+config POWER_RESET_VERSATILE
+	bool "ARM Versatile family reboot driver"
+	depends on ARM
+	depends on MFD_SYSCON
+	depends on OF
+	help
+	  Power off and restart support for ARM Versatile family of
+	  reference boards.
+
 config POWER_RESET_VEXPRESS
 	bool "ARM Versatile Express power-off and reset driver"
 	depends on ARM || ARM64

drivers/power/reset/Makefile

@@ -9,6 +9,7 @@ obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
 obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
 obj-$(CONFIG_POWER_RESET_RESTART) += restart-poweroff.o
 obj-$(CONFIG_POWER_RESET_SUN6I) += sun6i-reboot.o
+obj-$(CONFIG_POWER_RESET_VERSATILE) += arm-versatile-reboot.o
 obj-$(CONFIG_POWER_RESET_VEXPRESS) += vexpress-poweroff.o
 obj-$(CONFIG_POWER_RESET_XGENE) += xgene-reboot.o
 obj-$(CONFIG_POWER_RESET_KEYSTONE) += keystone-reset.o

drivers/power/reset/arm-versatile-reboot.c

+/*
+ * Copyright (C) 2014 Linaro Ltd.
+ *
+ * Author: Linus Walleij <linus.walleij@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+#include <linux/init.h>
+#include <linux/mfd/syscon.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+#include <linux/of.h>
+#include <asm/system_misc.h>
+
+#define REALVIEW_SYS_LOCK_OFFSET	0x20
+#define REALVIEW_SYS_LOCK_VAL		0xA05F
+#define REALVIEW_SYS_RESETCTL_OFFSET	0x40
+
+/*
+ * We detect the different syscon types from the compatible strings.
+ */
+enum versatile_reboot {
+	REALVIEW_REBOOT_EB,
+	REALVIEW_REBOOT_PB1176,
+	REALVIEW_REBOOT_PB11MP,
+	REALVIEW_REBOOT_PBA8,
+	REALVIEW_REBOOT_PBX,
+};
+
+/* Pointer to the system controller */
+static struct regmap *syscon_regmap;
+static enum versatile_reboot versatile_reboot_type;
+
+static const struct of_device_id versatile_reboot_of_match[] = {
+	{
+		.compatible = "arm,realview-eb-syscon",
+		.data = (void *)REALVIEW_REBOOT_EB,
+	},
+	{
+		.compatible = "arm,realview-pb1176-syscon",
+		.data = (void *)REALVIEW_REBOOT_PB1176,
+	},
+	{
+		.compatible = "arm,realview-pb11mp-syscon",
+		.data = (void *)REALVIEW_REBOOT_PB11MP,
+	},
+	{
+		.compatible = "arm,realview-pba8-syscon",
+		.data = (void *)REALVIEW_REBOOT_PBA8,
+	},
+	{
+		.compatible = "arm,realview-pbx-syscon",
+		.data = (void *)REALVIEW_REBOOT_PBX,
+	},
+};
+
+static void versatile_reboot(enum reboot_mode mode, const char *cmd)
+{
+	/* Unlock the reset register */
+	regmap_write(syscon_regmap, REALVIEW_SYS_LOCK_OFFSET,
+		     REALVIEW_SYS_LOCK_VAL);
+	/* Then hit reset on the different machines */
+	switch (versatile_reboot_type) {
+	case REALVIEW_REBOOT_EB:
+		regmap_write(syscon_regmap,
+			     REALVIEW_SYS_RESETCTL_OFFSET, 0x0008);
+		break;
+	case REALVIEW_REBOOT_PB1176:
+		regmap_write(syscon_regmap,
+			     REALVIEW_SYS_RESETCTL_OFFSET, 0x0100);
+		break;
+	case REALVIEW_REBOOT_PB11MP:
+	case REALVIEW_REBOOT_PBA8:
+		regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
+			     0x0000);
+		regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
+			     0x0004);
+		break;
+	case REALVIEW_REBOOT_PBX:
+		regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
+			     0x00f0);
+		regmap_write(syscon_regmap, REALVIEW_SYS_RESETCTL_OFFSET,
+			     0x00f4);
+		break;
+	}
+	dsb();
+}
+
+static int __init versatile_reboot_probe(void)
+{
+	const struct of_device_id *reboot_id;
+	struct device_node *np;
+
+	np = of_find_matching_node_and_match(NULL, versatile_reboot_of_match,
+						 &reboot_id);
+	if (!np)
+		return -ENODEV;
+	versatile_reboot_type = (enum versatile_reboot)reboot_id->data;
+
+	syscon_regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(syscon_regmap))
+		return PTR_ERR(syscon_regmap);
+
+	arm_pm_restart = versatile_reboot;
+	pr_info("versatile reboot driver registered\n");
+	return 0;
+}
+device_initcall(versatile_reboot_probe);