drivers/power/reset/syscon-poweroff.c

/*
 * Generic Syscon Poweroff Driver
 *
 * Copyright (c) 2015, National Instruments Corp.
 * Author: Moritz Fischer <moritz.fischer@ettus.com>
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/kallsyms.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/notifier.h>
#include <linux/mfd/syscon.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/platform_device.h>
#include <linux/pm.h>
#include <linux/regmap.h>

static struct regmap *map;
static u32 offset;
static u32 mask;

void syscon_poweroff(void)
{
	/* Issue the poweroff */
	regmap_write(map, offset, mask);

	mdelay(1000);

	pr_emerg("Unable to poweroff system\n");
}

static int syscon_poweroff_probe(struct platform_device *pdev)
{
	char symname[KSYM_NAME_LEN];

	map = syscon_regmap_lookup_by_phandle(pdev->dev.of_node, "regmap");
	if (IS_ERR(map)) {
		dev_err(&pdev->dev, "unable to get syscon");
		return PTR_ERR(map);
	}

	if (of_property_read_u32(pdev->dev.of_node, "offset", &offset)) {
		dev_err(&pdev->dev, "unable to read 'offset'");
		return -EINVAL;
	}

	if (of_property_read_u32(pdev->dev.of_node, "mask", &mask)) {
		dev_err(&pdev->dev, "unable to read 'mask'");
		return -EINVAL;
	}

	if (pm_power_off) {
		lookup_symbol_name((ulong)pm_power_off, symname);
		dev_err(&pdev->dev,
		"pm_power_off already claimed %p %s",
		pm_power_off, symname);
		return -EBUSY;
	}

	pm_power_off = syscon_poweroff;

	return 0;
}

static int syscon_poweroff_remove(struct platform_device *pdev)
{
	if (pm_power_off == syscon_poweroff)
		pm_power_off = NULL;

	return 0;
}

static const struct of_device_id syscon_poweroff_of_match[] = {
	{ .compatible = "syscon-poweroff" },
	{}
};

static struct platform_driver syscon_poweroff_driver = {
	.probe = syscon_poweroff_probe,
	.remove = syscon_poweroff_remove,
	.driver = {
		.name = "syscon-poweroff",
		.of_match_table = syscon_poweroff_of_match,
	},
};

static int __init syscon_poweroff_register(void)
{
	return platform_driver_register(&syscon_poweroff_driver);
}
device_initcall(syscon_poweroff_register);