// SPDX-License-Identifier: GPL-2.0+
/*
 *      NS pc87413-wdt Watchdog Timer driver for Linux 2.6.x.x
 *
 *      This code is based on wdt.c with original copyright.
 *
 *      (C) Copyright 2006 Sven Anders, <anders@anduras.de>
 *                     and Marcus Junker, <junker@anduras.de>
 *
 *      Neither Sven Anders, Marcus Junker nor ANDURAS AG
 *      admit liability nor provide warranty for any of this software.
 *      This material is provided "AS-IS" and at no charge.
 *
 *      Release 1.1
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/notifier.h>
#include <linux/fs.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/moduleparam.h>
#include <linux/io.h>
#include <linux/uaccess.h>


/* #define DEBUG 1 */

#define DEFAULT_TIMEOUT     1           /* 1 minute */
#define MAX_TIMEOUT         255

#define VERSION             "1.1"
#define MODNAME             "pc87413 WDT"
#define DPFX                MODNAME " - DEBUG: "

#define WDT_INDEX_IO_PORT   (io+0)      /* I/O port base (index register) */
#define WDT_DATA_IO_PORT    (WDT_INDEX_IO_PORT+1)
#define SWC_LDN             0x04
#define SIOCFG2             0x22        /* Serial IO register */
#define WDCTL               0x10        /* Watchdog-Timer-Control-Register */
#define WDTO                0x11        /* Watchdog timeout register */
#define WDCFG               0x12        /* Watchdog config register */

#define IO_DEFAULT      0x2E            /* Address used on Portwell Boards */

static int io = IO_DEFAULT;
static int swc_base_addr = -1;

static int timeout = DEFAULT_TIMEOUT;   /* timeout value */
static unsigned long timer_enabled;     /* is the timer enabled? */

static char expect_close;               /* is the close expected? */

static DEFINE_SPINLOCK(io_lock);        /* to guard us from io races */

static bool nowayout = WATCHDOG_NOWAYOUT;

/* -- Low level function ----------------------------------------*/

/* Select pins for Watchdog output */

static inline void pc87413_select_wdt_out(void)
{
        unsigned int cr_data = 0;

        /* Step 1: Select multiple pin,pin55,as WDT output */

        outb_p(SIOCFG2, WDT_INDEX_IO_PORT);

        cr_data = inb(WDT_DATA_IO_PORT);

        cr_data |= 0x80; /* Set Bit7 to 1*/
        outb_p(SIOCFG2, WDT_INDEX_IO_PORT);

        outb_p(cr_data, WDT_DATA_IO_PORT);

#ifdef DEBUG
        pr_info(DPFX
                "Select multiple pin,pin55,as WDT output: Bit7 to 1: %d\n",
                                                                cr_data);
#endif
}

/* Enable SWC functions */

static inline void pc87413_enable_swc(void)
{
        unsigned int cr_data = 0;

        /* Step 2: Enable SWC functions */

        outb_p(0x07, WDT_INDEX_IO_PORT);        /* Point SWC_LDN (LDN=4) */
        outb_p(SWC_LDN, WDT_DATA_IO_PORT);

        outb_p(0x30, WDT_INDEX_IO_PORT);        /* Read Index 0x30 First */
        cr_data = inb(WDT_DATA_IO_PORT);
        cr_data |= 0x01;                        /* Set Bit0 to 1 */
        outb_p(0x30, WDT_INDEX_IO_PORT);
        outb_p(cr_data, WDT_DATA_IO_PORT);      /* Index0x30_bit0P1 */

#ifdef DEBUG
        pr_info(DPFX "pc87413 - Enable SWC functions\n");
#endif
}

/* Read SWC I/O base address */

static void pc87413_get_swc_base_addr(void)
{
        unsigned char addr_l, addr_h = 0;

        /* Step 3: Read SWC I/O Base Address */

        outb_p(0x60, WDT_INDEX_IO_PORT);        /* Read Index 0x60 */
        addr_h = inb(WDT_DATA_IO_PORT);

        outb_p(0x61, WDT_INDEX_IO_PORT);        /* Read Index 0x61 */

        addr_l = inb(WDT_DATA_IO_PORT);

        swc_base_addr = (addr_h << 8) + addr_l;
#ifdef DEBUG
        pr_info(DPFX
                "Read SWC I/O Base Address: low %d, high %d, res %d\n",
                                                addr_l, addr_h, swc_base_addr);
#endif
}

/* Select Bank 3 of SWC */

static inline void pc87413_swc_bank3(void)
{
        /* Step 4: Select Bank3 of SWC */
        outb_p(inb(swc_base_addr + 0x0f) | 0x03, swc_base_addr + 0x0f);
#ifdef DEBUG
        pr_info(DPFX "Select Bank3 of SWC\n");
#endif
}

/* Set watchdog timeout to x minutes */

static inline void pc87413_programm_wdto(char pc87413_time)
{
        /* Step 5: Programm WDTO, Twd. */
        outb_p(pc87413_time, swc_base_addr + WDTO);
#ifdef DEBUG
        pr_info(DPFX "Set WDTO to %d minutes\n", pc87413_time);
#endif
}

/* Enable WDEN */

static inline void pc87413_enable_wden(void)
{
        /* Step 6: Enable WDEN */
        outb_p(inb(swc_base_addr + WDCTL) | 0x01, swc_base_addr + WDCTL);
#ifdef DEBUG
        pr_info(DPFX "Enable WDEN\n");
#endif
}

/* Enable SW_WD_TREN */
static inline void pc87413_enable_sw_wd_tren(void)
{
        /* Enable SW_WD_TREN */
        outb_p(inb(swc_base_addr + WDCFG) | 0x80, swc_base_addr + WDCFG);
#ifdef DEBUG
        pr_info(DPFX "Enable SW_WD_TREN\n");
#endif
}

/* Disable SW_WD_TREN */

static inline void pc87413_disable_sw_wd_tren(void)
{
        /* Disable SW_WD_TREN */
        outb_p(inb(swc_base_addr + WDCFG) & 0x7f, swc_base_addr + WDCFG);
#ifdef DEBUG
        pr_info(DPFX "pc87413 - Disable SW_WD_TREN\n");
#endif
}

/* Enable SW_WD_TRG */

static inline void pc87413_enable_sw_wd_trg(void)
{
        /* Enable SW_WD_TRG */
        outb_p(inb(swc_base_addr + WDCTL) | 0x80, swc_base_addr + WDCTL);
#ifdef DEBUG
        pr_info(DPFX "pc87413 - Enable SW_WD_TRG\n");
#endif
}

/* Disable SW_WD_TRG */

static inline void pc87413_disable_sw_wd_trg(void)
{
        /* Disable SW_WD_TRG */
        outb_p(inb(swc_base_addr + WDCTL) & 0x7f, swc_base_addr + WDCTL);
#ifdef DEBUG
        pr_info(DPFX "Disable SW_WD_TRG\n");
#endif
}

/* -- Higher level functions ------------------------------------*/

/* Enable the watchdog */

static void pc87413_enable(void)
{
        spin_lock(&io_lock);

        pc87413_swc_bank3();
        pc87413_programm_wdto(timeout);
        pc87413_enable_wden();
        pc87413_enable_sw_wd_tren();
        pc87413_enable_sw_wd_trg();

        spin_unlock(&io_lock);
}

/* Disable the watchdog */

static void pc87413_disable(void)
{
        spin_lock(&io_lock);

        pc87413_swc_bank3();
        pc87413_disable_sw_wd_tren();
        pc87413_disable_sw_wd_trg();
        pc87413_programm_wdto(0);

        spin_unlock(&io_lock);
}

/* Refresh the watchdog */

static void pc87413_refresh(void)
{
        spin_lock(&io_lock);

        pc87413_swc_bank3();
        pc87413_disable_sw_wd_tren();
        pc87413_disable_sw_wd_trg();
        pc87413_programm_wdto(timeout);
        pc87413_enable_wden();
        pc87413_enable_sw_wd_tren();
        pc87413_enable_sw_wd_trg();

        spin_unlock(&io_lock);
}

/* -- File operations -------------------------------------------*/

/**
 *      pc87413_open:
 *      @inode: inode of device
 *      @file: file handle to device
 *
 */

static int pc87413_open(struct inode *inode, struct file *file)
{
        /* /dev/watchdog can only be opened once */

        if (test_and_set_bit(0, &timer_enabled))
                return -EBUSY;

        if (nowayout)
                __module_get(THIS_MODULE);

        /* Reload and activate timer */
        pc87413_refresh();

        pr_info("Watchdog enabled. Timeout set to %d minute(s).\n", timeout);

        return stream_open(inode, file);
}

/**
 *      pc87413_release:
 *      @inode: inode to board
 *      @file: file handle to board
 *
 *      The watchdog has a configurable API. There is a religious dispute
 *      between people who want their watchdog to be able to shut down and
 *      those who want to be sure if the watchdog manager dies the machine
 *      reboots. In the former case we disable the counters, in the latter
 *      case you have to open it again very soon.
 */

static int pc87413_release(struct inode *inode, struct file *file)
{
        /* Shut off the timer. */

        if (expect_close == 42) {
                pc87413_disable();
                pr_info("Watchdog disabled, sleeping again...\n");
        } else {
                pr_crit("Unexpected close, not stopping watchdog!\n");
                pc87413_refresh();
        }
        clear_bit(0, &timer_enabled);
        expect_close = 0;
        return 0;
}

/**
 *      pc87413_status:
 *
 *      return, if the watchdog is enabled (timeout is set...)
 */


static int pc87413_status(void)
{
          return 0; /* currently not supported */
}

/**
 *      pc87413_write:
 *      @file: file handle to the watchdog
 *      @data: data buffer to write
 *      @len: length in bytes
 *      @ppos: pointer to the position to write. No seeks allowed
 *
 *      A write to a watchdog device is defined as a keepalive signal. Any
 *      write of data will do, as we we don't define content meaning.
 */

static ssize_t pc87413_write(struct file *file, const char __user *data,
                             size_t len, loff_t *ppos)
{
        /* See if we got the magic character 'V' and reload the timer */
        if (len) {
                if (!nowayout) {
                        size_t i;

                        /* reset expect flag */
                        expect_close = 0;

                        /* scan to see whether or not we got the
                           magic character */
                        for (i = 0; i != len; i++) {
                                char c;
                                if (get_user(c, data + i))
                                        return -EFAULT;
                                if (c == 'V')
                                        expect_close = 42;
                        }
                }

                /* someone wrote to us, we should reload the timer */
                pc87413_refresh();
        }
        return len;
}

/**
 *      pc87413_ioctl:
 *      @file: file handle to the device
 *      @cmd: watchdog command
 *      @arg: argument pointer
 *
 *      The watchdog API defines a common set of functions for all watchdogs
 *      according to their available features. We only actually usefully support
 *      querying capabilities and current status.
 */

static long pc87413_ioctl(struct file *file, unsigned int cmd,
                                                unsigned long arg)
{
        int new_timeout;

        union {
                struct watchdog_info __user *ident;
                int __user *i;
        } uarg;

        static const struct watchdog_info ident = {
                .options          = WDIOF_KEEPALIVEPING |
                                    WDIOF_SETTIMEOUT |
                                    WDIOF_MAGICCLOSE,
                .firmware_version = 1,
                .identity         = "PC87413(HF/F) watchdog",
        };

        uarg.i = (int __user *)arg;

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(uarg.ident, &ident,
                                        sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
                return put_user(pc87413_status(), uarg.i);
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, uarg.i);
        case WDIOC_SETOPTIONS:
        {
                int options, retval = -EINVAL;
                if (get_user(options, uarg.i))
                        return -EFAULT;
                if (options & WDIOS_DISABLECARD) {
                        pc87413_disable();
                        retval = 0;
                }
                if (options & WDIOS_ENABLECARD) {
                        pc87413_enable();
                        retval = 0;
                }
                return retval;
        }
        case WDIOC_KEEPALIVE:
                pc87413_refresh();
#ifdef DEBUG
                pr_info(DPFX "keepalive\n");
#endif
                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_timeout, uarg.i))
                        return -EFAULT;
                /* the API states this is given in secs */
                new_timeout /= 60;
                if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
                        return -EINVAL;
                timeout = new_timeout;
                pc87413_refresh();
                fallthrough;    /* and return the new timeout */
        case WDIOC_GETTIMEOUT:
                new_timeout = timeout * 60;
                return put_user(new_timeout, uarg.i);
        default:
                return -ENOTTY;
        }
}

/* -- Notifier funtions -----------------------------------------*/

/**
 *      pc87413_notify_sys:
 *      @this: our notifier block
 *      @code: the event being reported
 *      @unused: unused
 *
 *      Our notifier is called on system shutdowns. We want to turn the card
 *      off at reboot otherwise the machine will reboot again during memory
 *      test or worse yet during the following fsck. This would suck, in fact
 *      trust me - if it happens it does suck.
 */

static int pc87413_notify_sys(struct notifier_block *this,
                              unsigned long code,
                              void *unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                /* Turn the card off */
                pc87413_disable();
        return NOTIFY_DONE;
}

/* -- Module's structures ---------------------------------------*/

static const struct file_operations pc87413_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = pc87413_write,
        .unlocked_ioctl = pc87413_ioctl,
        .compat_ioctl   = compat_ptr_ioctl,
        .open           = pc87413_open,
        .release        = pc87413_release,
};

static struct notifier_block pc87413_notifier = {
        .notifier_call  = pc87413_notify_sys,
};

static struct miscdevice pc87413_miscdev = {
        .minor          = WATCHDOG_MINOR,
        .name           = "watchdog",
        .fops           = &pc87413_fops,
};

/* -- Module init functions -------------------------------------*/

/**
 *      pc87413_init: module's "constructor"
 *
 *      Set up the WDT watchdog board. All we have to do is grab the
 *      resources we require and bitch if anyone beat us to them.
 *      The open() function will actually kick the board off.
 */

static int __init pc87413_init(void)
{
        int ret;

        pr_info("Version " VERSION " at io 0x%X\n",
                                                        WDT_INDEX_IO_PORT);

        if (!request_muxed_region(io, 2, MODNAME))
                return -EBUSY;

        ret = register_reboot_notifier(&pc87413_notifier);
        if (ret != 0)
                pr_err("cannot register reboot notifier (err=%d)\n", ret);

        ret = misc_register(&pc87413_miscdev);
        if (ret != 0) {
                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
                       WATCHDOG_MINOR, ret);
                goto reboot_unreg;
        }
        pr_info("initialized. timeout=%d min\n", timeout);

        pc87413_select_wdt_out();
        pc87413_enable_swc();
        pc87413_get_swc_base_addr();

        if (!request_region(swc_base_addr, 0x20, MODNAME)) {
                pr_err("cannot request SWC region at 0x%x\n", swc_base_addr);
                ret = -EBUSY;
                goto misc_unreg;
        }

        pc87413_enable();

        release_region(io, 2);
        return 0;

misc_unreg:
        misc_deregister(&pc87413_miscdev);
reboot_unreg:
        unregister_reboot_notifier(&pc87413_notifier);
        release_region(io, 2);
        return ret;
}

/**
 *      pc87413_exit: module's "destructor"
 *
 *      Unload the watchdog. You cannot do this with any file handles open.
 *      If your watchdog is set to continue ticking on close and you unload
 *      it, well it keeps ticking. We won't get the interrupt but the board
 *      will not touch PC memory so all is fine. You just have to load a new
 *      module in 60 seconds or reboot.
 */

static void __exit pc87413_exit(void)
{
        /* Stop the timer before we leave */
        if (!nowayout) {
                pc87413_disable();
                pr_info("Watchdog disabled\n");
        }

        misc_deregister(&pc87413_miscdev);
        unregister_reboot_notifier(&pc87413_notifier);
        release_region(swc_base_addr, 0x20);

        pr_info("watchdog component driver removed\n");
}

module_init(pc87413_init);
module_exit(pc87413_exit);

MODULE_AUTHOR("Sven Anders <anders@anduras.de>");
MODULE_AUTHOR("Marcus Junker <junker@anduras.de>");
MODULE_DESCRIPTION("PC87413 WDT driver");
MODULE_LICENSE("GPL");

module_param_hw(io, int, ioport, 0);
MODULE_PARM_DESC(io, MODNAME " I/O port (default: "
                                        __MODULE_STRING(IO_DEFAULT) ").");

module_param(timeout, int, 0);
MODULE_PARM_DESC(timeout,
                "Watchdog timeout in minutes (default="
                                __MODULE_STRING(DEFAULT_TIMEOUT) ").");

module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout,
                "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");