power: reset: Add reset driver for R-Mobile platforms

Add a reset driver for Renesas R-Mobile and SH-Mobile SoCs. It registers
a restart handler to trigger a soft power-on reset through the R-Mobile
System Controller.
The priority of this restart handler is 192, to allow a watchdog driver
to use priority 128.

Note that we do not use syscon-reboot, as the HPB (Peripheral Bus
Bridge) semaphore should be acquired on systems where both the ARM and
SH core are in use. The driver can be extended later to support this,
when needed.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/reset/Kconfig

@@ -159,5 +159,11 @@ config POWER_RESET_SYSCON
 	help
 	  Reboot support for generic SYSCON mapped register reset.
 
+config POWER_RESET_RMOBILE
+	tristate "Renesas R-Mobile reset driver"
+	depends on ARCH_RMOBILE || COMPILE_TEST
+	help
+	  Reboot support for Renesas R-Mobile and SH-Mobile SoCs.
+
 endif
 

drivers/power/reset/Makefile

@@ -18,3 +18,4 @@ obj-$(CONFIG_POWER_RESET_VEXPRESS) += vexpress-poweroff.o
 obj-$(CONFIG_POWER_RESET_XGENE) += xgene-reboot.o
 obj-$(CONFIG_POWER_RESET_KEYSTONE) += keystone-reset.o
 obj-$(CONFIG_POWER_RESET_SYSCON) += syscon-reboot.o
+obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o

drivers/power/reset/rmobile-reset.c

@@ -0,0 +1,91 @@
+/*
+ * Renesas R-Mobile Reset Driver
+ *
+ * Copyright (C) 2014 Glider bvba
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/notifier.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/reboot.h>
+
+/* SYSC Register Bank 2 */
+#define RESCNT2		0x20		/* Reset Control Register 2 */
+
+/* Reset Control Register 2 */
+#define RESCNT2_PRES	0x80000000	/* Soft power-on reset */
+
+static void __iomem *sysc_base2;
+
+static int rmobile_reset_handler(struct notifier_block *this,
+				 unsigned long mode, void *cmd)
+{
+	pr_debug("%s %lu\n", __func__, mode);
+
+	/* Let's assume we have acquired the HPB semaphore */
+	writel(RESCNT2_PRES, sysc_base2 + RESCNT2);
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block rmobile_reset_nb = {
+	.notifier_call = rmobile_reset_handler,
+	.priority = 192,
+};
+
+static int rmobile_reset_probe(struct platform_device *pdev)
+{
+	int error;
+
+	sysc_base2 = of_iomap(pdev->dev.of_node, 1);
+	if (!sysc_base2)
+		return -ENODEV;
+
+	error = register_restart_handler(&rmobile_reset_nb);
+	if (error) {
+		dev_err(&pdev->dev,
+			"cannot register restart handler (err=%d)\n", error);
+		goto fail_unmap;
+	}
+
+	return 0;
+
+fail_unmap:
+	iounmap(sysc_base2);
+	return error;
+}
+
+static int rmobile_reset_remove(struct platform_device *pdev)
+{
+	unregister_restart_handler(&rmobile_reset_nb);
+	iounmap(sysc_base2);
+	return 0;
+}
+
+static const struct of_device_id rmobile_reset_of_match[] = {
+	{ .compatible = "renesas,sysc-rmobile", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, rmobile_reset_of_match);
+
+static struct platform_driver rmobile_reset_driver = {
+	.probe = rmobile_reset_probe,
+	.remove = rmobile_reset_remove,
+	.driver = {
+		.name = "rmobile_reset",
+		.of_match_table = rmobile_reset_of_match,
+	},
+};
+
+module_platform_driver(rmobile_reset_driver);
+
+MODULE_DESCRIPTION("Renesas R-Mobile Reset Driver");
+MODULE_AUTHOR("Geert Uytterhoeven <geert+renesas@glider.be>");
+MODULE_LICENSE("GPL v2");