power: reset: add reboot mode driver

This driver parses the reboot commands like "reboot bootloader"
and "reboot recovery" to get a boot mode described in the
device tree , then call the write interfae to store the boot
mode in some place like special register or sram, which can
be read by the bootloader after system reboot, then the bootloader
can take different action according to the mode stored.

This is commonly used on Android based devices, in order to
reboot the device into fastboot or recovery mode.

Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Reviewed-by: Moritz Fischer <moritz.fischer@ettus.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Acked-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Andy Yan <andy.yan@rock-chips.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

drivers/power/reset/Kconfig

@@ -184,5 +184,19 @@ config POWER_RESET_ZX
 	help
 	  Reboot support for ZTE SoCs.
 
+config REBOOT_MODE
+	tristate
+
+config SYSCON_REBOOT_MODE
+	tristate "Generic SYSCON regmap reboot mode driver"
+	depends on OF
+	select REBOOT_MODE
+	select MFD_SYSCON
+	help
+	  Say y here will enable reboot mode driver. This will
+	  get reboot mode arguments and store it in SYSCON mapped
+	  register, then the bootloader can read it to take different
+	  action according to the mode.
+
 endif
 

drivers/power/reset/Makefile

@@ -21,3 +21,5 @@ obj-$(CONFIG_POWER_RESET_SYSCON) += syscon-reboot.o
 obj-$(CONFIG_POWER_RESET_SYSCON_POWEROFF) += syscon-poweroff.o
 obj-$(CONFIG_POWER_RESET_RMOBILE) += rmobile-reset.o
 obj-$(CONFIG_POWER_RESET_ZX) += zx-reboot.o
+obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
+obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o

drivers/power/reset/reboot-mode.c

@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/reboot.h>
+#include "reboot-mode.h"
+
+#define PREFIX "mode-"
+
+struct mode_info {
+	const char *mode;
+	u32 magic;
+	struct list_head list;
+};
+
+static unsigned int get_reboot_mode_magic(struct reboot_mode_driver *reboot,
+					  const char *cmd)
+{
+	const char *normal = "normal";
+	int magic = 0;
+	struct mode_info *info;
+
+	if (!cmd)
+		cmd = normal;
+
+	list_for_each_entry(info, &reboot->head, list) {
+		if (!strcmp(info->mode, cmd)) {
+			magic = info->magic;
+			break;
+		}
+	}
+
+	return magic;
+}
+
+static int reboot_mode_notify(struct notifier_block *this,
+			      unsigned long mode, void *cmd)
+{
+	struct reboot_mode_driver *reboot;
+	unsigned int magic;
+
+	reboot = container_of(this, struct reboot_mode_driver, reboot_notifier);
+	magic = get_reboot_mode_magic(reboot, cmd);
+	if (magic)
+		reboot->write(reboot, magic);
+
+	return NOTIFY_DONE;
+}
+
+/**
+ * reboot_mode_register - register a reboot mode driver
+ * @reboot: reboot mode driver
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+int reboot_mode_register(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info;
+	struct property *prop;
+	struct device_node *np = reboot->dev->of_node;
+	size_t len = strlen(PREFIX);
+	int ret;
+
+	INIT_LIST_HEAD(&reboot->head);
+
+	for_each_property_of_node(np, prop) {
+		if (strncmp(prop->name, PREFIX, len))
+			continue;
+
+		info = devm_kzalloc(reboot->dev, sizeof(*info), GFP_KERNEL);
+		if (!info) {
+			ret = -ENOMEM;
+			goto error;
+		}
+
+		if (of_property_read_u32(np, prop->name, &info->magic)) {
+			dev_err(reboot->dev, "reboot mode %s without magic number\n",
+				info->mode);
+			devm_kfree(reboot->dev, info);
+			continue;
+		}
+
+		info->mode = kstrdup_const(prop->name + len, GFP_KERNEL);
+		if (!info->mode) {
+			ret =  -ENOMEM;
+			goto error;
+		} else if (info->mode[0] == '\0') {
+			kfree_const(info->mode);
+			ret = -EINVAL;
+			dev_err(reboot->dev, "invalid mode name(%s): too short!\n",
+				prop->name);
+			goto error;
+		}
+
+		list_add_tail(&info->list, &reboot->head);
+	}
+
+	reboot->reboot_notifier.notifier_call = reboot_mode_notify;
+	register_reboot_notifier(&reboot->reboot_notifier);
+
+	return 0;
+
+error:
+	list_for_each_entry(info, &reboot->head, list)
+		kfree_const(info->mode);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_register);
+
+/**
+ * reboot_mode_unregister - unregister a reboot mode driver
+ * @reboot: reboot mode driver
+ */
+int reboot_mode_unregister(struct reboot_mode_driver *reboot)
+{
+	struct mode_info *info;
+
+	unregister_reboot_notifier(&reboot->reboot_notifier);
+
+	list_for_each_entry(info, &reboot->head, list)
+		kfree_const(info->mode);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(reboot_mode_unregister);
+
+MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com");
+MODULE_DESCRIPTION("System reboot mode core library");
+MODULE_LICENSE("GPL v2");

drivers/power/reset/reboot-mode.h

@@ -0,0 +1,14 @@
+#ifndef __REBOOT_MODE_H__
+#define __REBOOT_MODE_H__
+
+struct reboot_mode_driver {
+	struct device *dev;
+	struct list_head head;
+	int (*write)(struct reboot_mode_driver *reboot, unsigned int magic);
+	struct notifier_block reboot_notifier;
+};
+
+int reboot_mode_register(struct reboot_mode_driver *reboot);
+int reboot_mode_unregister(struct reboot_mode_driver *reboot);
+
+#endif

drivers/power/reset/syscon-reboot-mode.c

@@ -0,0 +1,99 @@
+/*
+ * Copyright (c) 2016, Fuzhou Rockchip Electronics Co., Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+#include "reboot-mode.h"
+
+struct syscon_reboot_mode {
+	struct regmap *map;
+	struct reboot_mode_driver reboot;
+	u32 offset;
+	u32 mask;
+};
+
+static int syscon_reboot_mode_write(struct reboot_mode_driver *reboot,
+				    unsigned int magic)
+{
+	struct syscon_reboot_mode *syscon_rbm;
+	int ret;
+
+	syscon_rbm = container_of(reboot, struct syscon_reboot_mode, reboot);
+
+	ret = regmap_update_bits(syscon_rbm->map, syscon_rbm->offset,
+				 syscon_rbm->mask, magic);
+	if (ret < 0)
+		dev_err(reboot->dev, "update reboot mode bits failed\n");
+
+	return ret;
+}
+
+static int syscon_reboot_mode_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct syscon_reboot_mode *syscon_rbm;
+
+	syscon_rbm = devm_kzalloc(&pdev->dev, sizeof(*syscon_rbm), GFP_KERNEL);
+	if (!syscon_rbm)
+		return -ENOMEM;
+
+	syscon_rbm->reboot.dev = &pdev->dev;
+	syscon_rbm->reboot.write = syscon_reboot_mode_write;
+	syscon_rbm->mask = 0xffffffff;
+
+	dev_set_drvdata(&pdev->dev, syscon_rbm);
+
+	syscon_rbm->map = syscon_node_to_regmap(pdev->dev.parent->of_node);
+	if (IS_ERR(syscon_rbm->map))
+		return PTR_ERR(syscon_rbm->map);
+
+	if (of_property_read_u32(pdev->dev.of_node, "offset",
+	    &syscon_rbm->offset))
+		return -EINVAL;
+
+	of_property_read_u32(pdev->dev.of_node, "mask", &syscon_rbm->mask);
+
+	ret = reboot_mode_register(&syscon_rbm->reboot);
+	if (ret)
+		dev_err(&pdev->dev, "can't register reboot mode\n");
+
+	return ret;
+}
+
+static int syscon_reboot_mode_remove(struct platform_device *pdev)
+{
+	struct syscon_reboot_mode *syscon_rbm = dev_get_drvdata(&pdev->dev);
+
+	return reboot_mode_unregister(&syscon_rbm->reboot);
+}
+
+static const struct of_device_id syscon_reboot_mode_of_match[] = {
+	{ .compatible = "syscon-reboot-mode" },
+	{}
+};
+
+static struct platform_driver syscon_reboot_mode_driver = {
+	.probe = syscon_reboot_mode_probe,
+	.remove = syscon_reboot_mode_remove,
+	.driver = {
+		.name = "syscon-reboot-mode",
+		.of_match_table = syscon_reboot_mode_of_match,
+	},
+};
+module_platform_driver(syscon_reboot_mode_driver);
+
+MODULE_AUTHOR("Andy Yan <andy.yan@rock-chips.com");
+MODULE_DESCRIPTION("SYSCON reboot mode driver");
+MODULE_LICENSE("GPL v2");