// SPDX-License-Identifier: GPL-2.0-or-later

  /*

   * GE watchdog userspace interface

   *

   * Author:  Martyn Welch <martyn.welch@ge.com>

   *

   * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.

   *

   * Based on: mv64x60_wdt.c (MV64X60 watchdog userspace interface)
   *   Author: James Chapman <jchapman@katalix.com>
   */
  
  /* TODO:
   * This driver does not provide support for the hardwares capability of sending
   * an interrupt at a programmable threshold.
   *
   * This driver currently can only support 1 watchdog - there are 2 in the
   * hardware that this driver supports. Thus one could be configured as a
   * process-based watchdog (via /dev/watchdog), the second (using the interrupt
   * capabilities) a kernel-based watchdog.
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

  #include <linux/kernel.h>
  #include <linux/compiler.h>
  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/miscdevice.h>
  #include <linux/watchdog.h>

  #include <linux/fs.h>

  #include <linux/of.h>

  #include <linux/of_address.h>

  #include <linux/of_platform.h>
  #include <linux/io.h>
  #include <linux/uaccess.h>
  
  #include <sysdev/fsl_soc.h>
  
  /*
   * The watchdog configuration register contains a pair of 2-bit fields,
   *   1.  a reload field, bits 27-26, which triggers a reload of
   *       the countdown register, and
   *   2.  an enable field, bits 25-24, which toggles between
   *       enabling and disabling the watchdog timer.
   * Bit 31 is a read-only field which indicates whether the
   * watchdog timer is currently enabled.
   *
   * The low 24 bits contain the timer reload value.
   */
  #define GEF_WDC_ENABLE_SHIFT	24
  #define GEF_WDC_SERVICE_SHIFT	26
  #define GEF_WDC_ENABLED_SHIFT	31
  
  #define GEF_WDC_ENABLED_TRUE	1
  #define GEF_WDC_ENABLED_FALSE	0
  
  /* Flags bits */
  #define GEF_WDOG_FLAG_OPENED	0
  
  static unsigned long wdt_flags;
  static int wdt_status;
  static void __iomem *gef_wdt_regs;
  static int gef_wdt_timeout;
  static int gef_wdt_count;
  static unsigned int bus_clk;
  static char expect_close;
  static DEFINE_SPINLOCK(gef_wdt_spinlock);

  static bool nowayout = WATCHDOG_NOWAYOUT;
  module_param(nowayout, bool, 0);

  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  
  
  static int gef_wdt_toggle_wdc(int enabled_predicate, int field_shift)
  {
  	u32 data;
  	u32 enabled;
  	int ret = 0;
  
  	spin_lock(&gef_wdt_spinlock);
  	data = ioread32be(gef_wdt_regs);
  	enabled = (data >> GEF_WDC_ENABLED_SHIFT) & 1;
  
  	/* only toggle the requested field if enabled state matches predicate */
  	if ((enabled ^ enabled_predicate) == 0) {
  		/* We write a 1, then a 2 -- to the appropriate field */
  		data = (1 << field_shift) | gef_wdt_count;
  		iowrite32be(data, gef_wdt_regs);
  
  		data = (2 << field_shift) | gef_wdt_count;
  		iowrite32be(data, gef_wdt_regs);
  		ret = 1;
  	}
  	spin_unlock(&gef_wdt_spinlock);
  
  	return ret;
  }
  
  static void gef_wdt_service(void)
  {
  	gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
  		GEF_WDC_SERVICE_SHIFT);
  }
  
  static void gef_wdt_handler_enable(void)
  {
  	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_FALSE,
  				   GEF_WDC_ENABLE_SHIFT)) {
  		gef_wdt_service();

  		pr_notice("watchdog activated
  ");

  	}
  }
  
  static void gef_wdt_handler_disable(void)
  {
  	if (gef_wdt_toggle_wdc(GEF_WDC_ENABLED_TRUE,
  				   GEF_WDC_ENABLE_SHIFT))

  		pr_notice("watchdog deactivated
  ");

  }
  
  static void gef_wdt_set_timeout(unsigned int timeout)
  {
  	/* maximum bus cycle count is 0xFFFFFFFF */
  	if (timeout > 0xFFFFFFFF / bus_clk)
  		timeout = 0xFFFFFFFF / bus_clk;
  
  	/* Register only holds upper 24 bits, bit shifted into lower 24 */
  	gef_wdt_count = (timeout * bus_clk) >> 8;
  	gef_wdt_timeout = timeout;
  }
  
  
  static ssize_t gef_wdt_write(struct file *file, const char __user *data,
  				 size_t len, loff_t *ppos)
  {
  	if (len) {
  		if (!nowayout) {
  			size_t i;
  
  			expect_close = 0;
  
  			for (i = 0; i != len; i++) {
  				char c;
  				if (get_user(c, data + i))
  					return -EFAULT;
  				if (c == 'V')
  					expect_close = 42;
  			}
  		}
  		gef_wdt_service();
  	}
  
  	return len;
  }
  
  static long gef_wdt_ioctl(struct file *file, unsigned int cmd,
  							unsigned long arg)
  {
  	int timeout;
  	int options;
  	void __user *argp = (void __user *)arg;

  	static const struct watchdog_info info = {

  		.options =	WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE |
  				WDIOF_KEEPALIVEPING,
  		.firmware_version = 0,

  		.identity = "GE watchdog",

  	};
  
  	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(wdt_status, (int __user *)argp))
  			return -EFAULT;
  		wdt_status &= ~WDIOF_KEEPALIVEPING;
  		break;
  
  	case WDIOC_SETOPTIONS:
  		if (get_user(options, (int __user *)argp))
  			return -EFAULT;
  
  		if (options & WDIOS_DISABLECARD)
  			gef_wdt_handler_disable();
  
  		if (options & WDIOS_ENABLECARD)
  			gef_wdt_handler_enable();
  		break;
  
  	case WDIOC_KEEPALIVE:
  		gef_wdt_service();
  		wdt_status |= WDIOF_KEEPALIVEPING;
  		break;
  
  	case WDIOC_SETTIMEOUT:
  		if (get_user(timeout, (int __user *)argp))
  			return -EFAULT;
  		gef_wdt_set_timeout(timeout);

  		fallthrough;

  
  	case WDIOC_GETTIMEOUT:
  		if (put_user(gef_wdt_timeout, (int __user *)argp))
  			return -EFAULT;
  		break;
  
  	default:
  		return -ENOTTY;
  	}
  
  	return 0;
  }
  
  static int gef_wdt_open(struct inode *inode, struct file *file)
  {
  	if (test_and_set_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags))
  		return -EBUSY;
  
  	if (nowayout)
  		__module_get(THIS_MODULE);
  
  	gef_wdt_handler_enable();

  	return stream_open(inode, file);

  }
  
  static int gef_wdt_release(struct inode *inode, struct file *file)
  {
  	if (expect_close == 42)
  		gef_wdt_handler_disable();
  	else {

  		pr_crit("unexpected close, not stopping timer!
  ");

  		gef_wdt_service();
  	}
  	expect_close = 0;
  
  	clear_bit(GEF_WDOG_FLAG_OPENED, &wdt_flags);
  
  	return 0;
  }
  
  static const struct file_operations gef_wdt_fops = {
  	.owner = THIS_MODULE,
  	.llseek = no_llseek,
  	.write = gef_wdt_write,
  	.unlocked_ioctl = gef_wdt_ioctl,

  	.compat_ioctl	= compat_ptr_ioctl,

  	.open = gef_wdt_open,
  	.release = gef_wdt_release,
  };
  
  static struct miscdevice gef_wdt_miscdev = {
  	.minor = WATCHDOG_MINOR,
  	.name = "watchdog",
  	.fops = &gef_wdt_fops,
  };

  static int gef_wdt_probe(struct platform_device *dev)

  {
  	int timeout = 10;
  	u32 freq;
  
  	bus_clk = 133; /* in MHz */
  
  	freq = fsl_get_sys_freq();

  	if (freq != -1)

  		bus_clk = freq;
  
  	/* Map devices registers into memory */

  	gef_wdt_regs = of_iomap(dev->dev.of_node, 0);

  	if (gef_wdt_regs == NULL)
  		return -ENOMEM;
  
  	gef_wdt_set_timeout(timeout);
  
  	gef_wdt_handler_disable();	/* in case timer was already running */
  
  	return misc_register(&gef_wdt_miscdev);
  }

  static int gef_wdt_remove(struct platform_device *dev)

  {
  	misc_deregister(&gef_wdt_miscdev);
  
  	gef_wdt_handler_disable();
  
  	iounmap(gef_wdt_regs);
  
  	return 0;
  }
  
  static const struct of_device_id gef_wdt_ids[] = {
  	{
  		.compatible = "gef,fpga-wdt",
  	},
  	{},
  };

  MODULE_DEVICE_TABLE(of, gef_wdt_ids);

  static struct platform_driver gef_wdt_driver = {

  	.driver = {
  		.name = "gef_wdt",

  		.of_match_table = gef_wdt_ids,
  	},

  	.probe		= gef_wdt_probe,

  	.remove		= gef_wdt_remove,

  };
  
  static int __init gef_wdt_init(void)
  {

  	pr_info("GE watchdog driver
  ");

  	return platform_driver_register(&gef_wdt_driver);

  }
  
  static void __exit gef_wdt_exit(void)
  {

  	platform_driver_unregister(&gef_wdt_driver);

  }
  
  module_init(gef_wdt_init);
  module_exit(gef_wdt_exit);

  MODULE_AUTHOR("Martyn Welch <martyn.welch@ge.com>");
  MODULE_DESCRIPTION("GE watchdog driver");

  MODULE_LICENSE("GPL");

  MODULE_ALIAS("platform:gef_wdt");