// 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/platform_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_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);
                fallthrough;

        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,
        .unlocked_ioctl =       riowd_ioctl,
        .compat_ioctl   =       compat_ptr_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\n");
                goto out;
        }
        /* Make miscdev useable right away */
        riowd_device = p;

        err = misc_register(&riowd_miscdev);
        if (err) {
                pr_err("Cannot register watchdog misc device\n");
                goto out_iounmap;
        }

        pr_info("Hardware watchdog [%i minutes], regs at %p\n",
                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 void 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);
}

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);