1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Toggles a GPIO pin to restart a device
  4 *
  5 * Copyright (C) 2014 Google, Inc.
  6 *
  7 * Based on the gpio-poweroff driver.
  8 */
  9#include <linux/reboot.h>
 10#include <linux/kernel.h>
 11#include <linux/init.h>
 12#include <linux/delay.h>
 13#include <linux/platform_device.h>
 14#include <linux/gpio/consumer.h>
 15#include <linux/module.h>
 16#include <linux/of.h>
 17
 18struct gpio_restart {
 19	struct gpio_desc *reset_gpio;
 20	u32 active_delay_ms;
 21	u32 inactive_delay_ms;
 22	u32 wait_delay_ms;
 23};
 24
 25static int gpio_restart_notify(struct sys_off_data *data)
 26{
 27	struct gpio_restart *gpio_restart = data->cb_data;
 28
 29	/* drive it active, also inactive->active edge */
 30	gpiod_direction_output(gpio_restart->reset_gpio, 1);
 31	mdelay(gpio_restart->active_delay_ms);
 32
 33	/* drive inactive, also active->inactive edge */
 34	gpiod_set_value(gpio_restart->reset_gpio, 0);
 35	mdelay(gpio_restart->inactive_delay_ms);
 36
 37	/* drive it active, also inactive->active edge */
 38	gpiod_set_value(gpio_restart->reset_gpio, 1);
 39
 40	/* give it some time */
 41	mdelay(gpio_restart->wait_delay_ms);
 42
 43	WARN_ON(1);
 44
 45	return NOTIFY_DONE;
 46}
 47
 48static int gpio_restart_probe(struct platform_device *pdev)
 49{
 50	struct gpio_restart *gpio_restart;
 51	bool open_source = false;
 52	int priority = 129;
 53	u32 property;
 54	int ret;
 55
 56	gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
 57			GFP_KERNEL);
 58	if (!gpio_restart)
 59		return -ENOMEM;
 60
 61	open_source = of_property_read_bool(pdev->dev.of_node, "open-source");
 62
 63	gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
 64			open_source ? GPIOD_IN : GPIOD_OUT_LOW);
 65	ret = PTR_ERR_OR_ZERO(gpio_restart->reset_gpio);
 66	if (ret) {
 67		if (ret != -EPROBE_DEFER)
 68			dev_err(&pdev->dev, "Could not get reset GPIO\n");
 69		return ret;
 70	}
 71
 72	gpio_restart->active_delay_ms = 100;
 73	gpio_restart->inactive_delay_ms = 100;
 74	gpio_restart->wait_delay_ms = 3000;
 75
 76	ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
 77	if (!ret) {
 78		if (property > 255)
 79			dev_err(&pdev->dev, "Invalid priority property: %u\n",
 80					property);
 81		else
 82			priority = property;
 83	}
 84
 85	of_property_read_u32(pdev->dev.of_node, "active-delay",
 86			&gpio_restart->active_delay_ms);
 87	of_property_read_u32(pdev->dev.of_node, "inactive-delay",
 88			&gpio_restart->inactive_delay_ms);
 89	of_property_read_u32(pdev->dev.of_node, "wait-delay",
 90			&gpio_restart->wait_delay_ms);
 91
 92	ret = devm_register_sys_off_handler(&pdev->dev,
 93					    SYS_OFF_MODE_RESTART,
 94					    priority,
 95					    gpio_restart_notify,
 96					    gpio_restart);
 97	if (ret) {
 98		dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
 99				__func__, ret);
100		return -ENODEV;
101	}
102
103	return 0;
104}
105
106static const struct of_device_id of_gpio_restart_match[] = {
107	{ .compatible = "gpio-restart", },
108	{},
109};
110
111static struct platform_driver gpio_restart_driver = {
112	.probe = gpio_restart_probe,
113	.driver = {
114		.name = "restart-gpio",
115		.of_match_table = of_gpio_restart_match,
116	},
117};
118
119module_platform_driver(gpio_restart_driver);
120
121MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
122MODULE_DESCRIPTION("GPIO restart driver");