/*
 * Copyright (C) 2013-2014 Dropcam
 * All rights reserved.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/interrupt.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/workqueue.h>
#include <linux/gpio.h>
#include <linux/of_gpio.h>

#include <asm/uaccess.h>
#include <asm/io.h>

#define  TPS3813_WDT_HALF_CYCLE_TIME      ((HZ * 550)/1000)
#define  KERNEL_HEARTBEAT_EXPIRE_TIMEOUT         (HZ * 10)  /* 10 seconds */

static struct workqueue_struct *tps3813_kernel_heartbeat;

struct tps3813_info {
	int last_toggle_value;
	struct timer_list * ptimer;
	unsigned long last_kernel_heartbeat;
	struct work_struct tps3813_work;

	int wdi_gpio;
	int enable_gpio;
};

static struct timer_list tps3813_timer;

static void tps3813_heartbeat_worker(struct work_struct *work) {
	struct tps3813_info *wdt_info = container_of(work, struct tps3813_info, tps3813_work);
	wdt_info->last_kernel_heartbeat = jiffies;
}

static void tps3813_toggle_timer_handler(unsigned long data)
{
	struct tps3813_info *wdt_info =
		(struct tps3813_info *)data;

	queue_work(tps3813_kernel_heartbeat, &wdt_info->tps3813_work);

	/* this timer interrupt handler might still fire after kernel panic
	 * kick the watchdog only if the kernel is alive */
	if (jiffies - wdt_info->last_kernel_heartbeat < KERNEL_HEARTBEAT_EXPIRE_TIMEOUT) {
		wdt_info->last_toggle_value = !wdt_info->last_toggle_value;

		gpio_set_value(wdt_info->wdi_gpio, wdt_info->last_toggle_value);

		mod_timer(wdt_info->ptimer, jiffies + TPS3813_WDT_HALF_CYCLE_TIME);
	}
}

struct tps3813_info *tps3813_of_populate_pdata(struct device *dev,
							  struct device_node *np)
{
	struct tps3813_info *pdata;
	pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
	if (!pdata)
		return ERR_PTR(-ENOMEM);

	pdata->wdi_gpio = of_get_named_gpio(np, "wdi-gpio", 0);
	pdata->enable_gpio = of_get_named_gpio(np, "enable-gpio", 0);

	return pdata;
}
EXPORT_SYMBOL_GPL(tps3813_of_populate_pdata);

static int tps3813_probe(struct platform_device *pdev)
{
	int errorCode = 0;
	struct tps3813_info *pdata;
	struct device_node *np = pdev->dev.of_node;

	if (np) {
		pdata = tps3813_of_populate_pdata(&pdev->dev, np);
		if (IS_ERR(pdata))
			return PTR_ERR(pdata);
	} else {
		dev_err(&pdev->dev, "no platform data\n");
		return -EINVAL;
	}

	dev_info(&pdev->dev, "Enabling WDT");
	errorCode = gpio_request(pdata->enable_gpio, dev_name(&pdev->dev));

	if (errorCode == -EPROBE_DEFER)
		return errorCode;

	if (errorCode) {
		dev_err(&pdev->dev, "Failed to request enable gpio: %d\n", errorCode);
		goto err_gpio_free;
	}
	errorCode = gpio_direction_output(pdata->enable_gpio, 1);
	if (errorCode) {
		dev_err(&pdev->dev, "Failed to set enable gpio to output: %d\n", errorCode);
		goto err_gpio_free;
	}

	errorCode = gpio_request(pdata->wdi_gpio, dev_name(&pdev->dev));
	if (errorCode) {
		dev_err(&pdev->dev, "Failed to request enable gpio: %d\n", errorCode);
		goto err_gpio_free;
	}
	errorCode = gpio_direction_output(pdata->wdi_gpio, pdata->last_toggle_value);
	if (errorCode) {
		dev_err(&pdev->dev, "Failed to set enable gpio to output: %d\n", errorCode);
		goto err_gpio_free;
	}

	pdata->last_toggle_value = 0;

	pdata->ptimer = &tps3813_timer;
	init_timer(pdata->ptimer);

	pdata->ptimer->function = tps3813_toggle_timer_handler;
	pdata->ptimer->data = (unsigned long)pdata;

	pdata->ptimer->expires = jiffies + TPS3813_WDT_HALF_CYCLE_TIME;

	tps3813_kernel_heartbeat = create_workqueue("tps3813_kernel_heartbeat");
	INIT_WORK(&pdata->tps3813_work, tps3813_heartbeat_worker);

	add_timer(pdata->ptimer);
	pdata->last_kernel_heartbeat = jiffies;

	// do first kick
	tps3813_toggle_timer_handler((unsigned long)pdata);

	platform_set_drvdata(pdev, pdata);

	goto tps3813_ok;

err_gpio_free:
	if (gpio_is_valid(pdata->enable_gpio))
		gpio_free(pdata->enable_gpio);

	if (gpio_is_valid(pdata->wdi_gpio))
		gpio_free(pdata->wdi_gpio);

tps3813_ok:
	return errorCode;
}


static int tps3813_remove(struct platform_device *pdev)
{
	struct tps3813_info *pinfo;
	int                 errorCode = 0;

	pinfo = platform_get_drvdata(pdev);

	dev_info(&pdev->dev, "Disabling WDT");

	gpio_set_value(pinfo->enable_gpio, 0);

	destroy_workqueue(tps3813_kernel_heartbeat);
	del_timer(&tps3813_timer);

	gpio_free(pinfo->enable_gpio);
	gpio_free(pinfo->wdi_gpio);

	kfree(pinfo);
	return errorCode;
}

static void tps3813_shutdown(struct platform_device *pdev)
{
	dev_info(&pdev->dev, "Disabling WDT");
	del_timer(&tps3813_timer);
}

static const struct of_device_id tps3813_match[] = {
	{ .compatible = "tps3813" },
	{ }
};
MODULE_DEVICE_TABLE(of, tps3813_match);

static struct platform_driver tps3813_driver = {
	.probe      = tps3813_probe,
	.remove     = tps3813_remove,
	.shutdown   = tps3813_shutdown,
	.driver     = {
		.name   = "tps3813",
		.owner  = THIS_MODULE,
		.of_match_table = tps3813_match,
	},
};

static int __init tps3813_init(void)
{
	return platform_driver_register(&tps3813_driver);
}

static void __exit tps3813_exit(void)
{
	platform_driver_unregister(&tps3813_driver);
}

module_init(tps3813_init);
module_exit(tps3813_exit);

MODULE_DESCRIPTION("TPS3813 Watch Dog Timer");
MODULE_AUTHOR("Jonathan Miles, <jonathan.miles@teknique.com>");
MODULE_LICENSE("GPL");