// SPDX-License-Identifier: GPL-2.0-only

  /* riowd.c - driver for hw watchdog inside Super I/O of RIO

   *

   * Copyright (C) 2001, 2008 David S. Miller (davem@davemloft.net)

   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/fs.h>
  #include <linux/errno.h>

  #include <linux/miscdevice.h>

  #include <linux/watchdog.h>
  #include <linux/of.h>
  #include <linux/of_device.h>

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

  #include <linux/slab.h>

  
  /* RIO uses the NatSemi Super I/O power management logical device
   * as its' watchdog.
   *
   * When the watchdog triggers, it asserts a line to the BBC (Boot Bus
   * Controller) of the machine.  The BBC can only be configured to
   * trigger a power-on reset when the signal is asserted.  The BBC
   * can be configured to ignore the signal entirely as well.
   *
   * The only Super I/O device register we care about is at index
   * 0x05 (WDTO_INDEX) which is the watchdog time-out in minutes (1-255).
   * If set to zero, this disables the watchdog.  When set, the system
   * must periodically (before watchdog expires) clear (set to zero) and
   * re-set the watchdog else it will trigger.
   *
   * There are two other indexed watchdog registers inside this Super I/O
   * logical device, but they are unused.  The first, at index 0x06 is
   * the watchdog control and can be used to make the watchdog timer re-set
   * when the PS/2 mouse or serial lines show activity.  The second, at
   * index 0x07 is merely a sampling of the line from the watchdog to the
   * BBC.
   *
   * The watchdog device generates no interrupts.
   */

  MODULE_AUTHOR("David S. Miller <davem@davemloft.net>");

  MODULE_DESCRIPTION("Hardware watchdog driver for Sun RIO");
  MODULE_SUPPORTED_DEVICE("watchdog");
  MODULE_LICENSE("GPL");

  #define DRIVER_NAME	"riowd"
  #define PFX		DRIVER_NAME ": "

  struct riowd {
  	void __iomem		*regs;
  	spinlock_t		lock;
  };
  
  static struct riowd *riowd_device;

  #define WDTO_INDEX	0x05
  
  static int riowd_timeout = 1;		/* in minutes */
  module_param(riowd_timeout, int, 0);
  MODULE_PARM_DESC(riowd_timeout, "Watchdog timeout in minutes");

  static void riowd_writereg(struct riowd *p, u8 val, int index)

  {
  	unsigned long flags;

  	spin_lock_irqsave(&p->lock, flags);
  	writeb(index, p->regs + 0);
  	writeb(val, p->regs + 1);
  	spin_unlock_irqrestore(&p->lock, flags);

  }
  
  static int riowd_open(struct inode *inode, struct file *filp)
  {

  	stream_open(inode, filp);

  	return 0;
  }
  
  static int riowd_release(struct inode *inode, struct file *filp)
  {
  	return 0;
  }

  static long riowd_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)

  {

  	static const struct watchdog_info info = {

  		.options		= WDIOF_SETTIMEOUT,
  		.firmware_version	= 1,

  		.identity		= DRIVER_NAME,

  	};
  	void __user *argp = (void __user *)arg;

  	struct riowd *p = riowd_device;

  	unsigned int options;
  	int new_margin;
  
  	switch (cmd) {
  	case WDIOC_GETSUPPORT:
  		if (copy_to_user(argp, &info, sizeof(info)))
  			return -EFAULT;
  		break;
  
  	case WDIOC_GETSTATUS:
  	case WDIOC_GETBOOTSTATUS:
  		if (put_user(0, (int __user *)argp))
  			return -EFAULT;
  		break;
  
  	case WDIOC_KEEPALIVE:

  		riowd_writereg(p, riowd_timeout, WDTO_INDEX);

  		break;
  
  	case WDIOC_SETOPTIONS:
  		if (copy_from_user(&options, argp, sizeof(options)))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD)

  			riowd_writereg(p, 0, WDTO_INDEX);

  		else if (options & WDIOS_ENABLECARD)

  			riowd_writereg(p, riowd_timeout, WDTO_INDEX);

  		else
  			return -EINVAL;
  
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		if (get_user(new_margin, (int __user *)argp))
  			return -EFAULT;
  		if ((new_margin < 60) || (new_margin > (255 * 60)))

  			return -EINVAL;

  		riowd_timeout = (new_margin + 59) / 60;

  		riowd_writereg(p, riowd_timeout, WDTO_INDEX);

  		/* Fall through */

  
  	case WDIOC_GETTIMEOUT:
  		return put_user(riowd_timeout * 60, (int __user *)argp);
  
  	default:
  		return -EINVAL;
  	};
  
  	return 0;
  }

  static ssize_t riowd_write(struct file *file, const char __user *buf,
  						size_t count, loff_t *ppos)

  {

  	struct riowd *p = riowd_device;

  	if (count) {

  		riowd_writereg(p, riowd_timeout, WDTO_INDEX);

  		return 1;
  	}
  
  	return 0;
  }

  static const struct file_operations riowd_fops = {

  	.owner =		THIS_MODULE,
  	.llseek =		no_llseek,
  	.unlocked_ioctl =	riowd_ioctl,
  	.open =			riowd_open,
  	.write =		riowd_write,
  	.release =		riowd_release,

  };

  static struct miscdevice riowd_miscdev = {
  	.minor	= WATCHDOG_MINOR,
  	.name	= "watchdog",
  	.fops	= &riowd_fops
  };

  static int riowd_probe(struct platform_device *op)

  {

  	struct riowd *p;
  	int err = -EINVAL;

  	if (riowd_device)
  		goto out;

  	err = -ENOMEM;

  	p = devm_kzalloc(&op->dev, sizeof(*p), GFP_KERNEL);

  	if (!p)
  		goto out;

  	spin_lock_init(&p->lock);

  	p->regs = of_ioremap(&op->resource[0], 0, 2, DRIVER_NAME);

  	if (!p->regs) {

  		pr_err("Cannot map registers
  ");

  		goto out;

  	}

  	/* Make miscdev useable right away */
  	riowd_device = p;

  	err = misc_register(&riowd_miscdev);
  	if (err) {

  		pr_err("Cannot register watchdog misc device
  ");

  		goto out_iounmap;

  	}

  	pr_info("Hardware watchdog [%i minutes], regs at %p
  ",
  		riowd_timeout, p->regs);

  	platform_set_drvdata(op, p);

  	return 0;

  out_iounmap:

  	riowd_device = NULL;

  	of_iounmap(&op->resource[0], p->regs, 2);

  out:
  	return err;

  }

  static int riowd_remove(struct platform_device *op)

  {

  	struct riowd *p = platform_get_drvdata(op);

  	misc_deregister(&riowd_miscdev);

  	of_iounmap(&op->resource[0], p->regs, 2);

  
  	return 0;
  }

  static const struct of_device_id riowd_match[] = {

  	{
  		.name = "pmc",
  	},
  	{},
  };
  MODULE_DEVICE_TABLE(of, riowd_match);

  static struct platform_driver riowd_driver = {

  	.driver = {
  		.name = DRIVER_NAME,

  		.of_match_table = riowd_match,
  	},

  	.probe		= riowd_probe,

  	.remove		= riowd_remove,

  };

  module_platform_driver(riowd_driver);