/*
 *      Intel_SCU 0.2:  An Intel SCU IOH Based Watchdog Device
 *                      for Intel part #(s):
 *                              - AF82MP20 PCH
 *
 *      Copyright (C) 2009-2010 Intel Corporation. All rights reserved.
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of version 2 of the GNU General
 *      Public License as published by the Free Software Foundation.
 *
 *      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.
 *      The full GNU General Public License is included in this
 *      distribution in the file called COPYING.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/compiler.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <linux/jiffies.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/signal.h>
#include <linux/sfi.h>
#include <asm/irq.h>
#include <linux/atomic.h>
#include <asm/intel_scu_ipc.h>
#include <asm/apb_timer.h>
#include <asm/intel-mid.h>

#include "intel_scu_watchdog.h"

/* Bounds number of times we will retry loading time count */
/* This retry is a work around for a silicon bug.          */
#define MAX_RETRY 16

#define IPC_SET_WATCHDOG_TIMER  0xF8

static int timer_margin = DEFAULT_SOFT_TO_HARD_MARGIN;
module_param(timer_margin, int, 0);
MODULE_PARM_DESC(timer_margin,
                "Watchdog timer margin"
                "Time between interrupt and resetting the system"
                "The range is from 1 to 160"
                "This is the time for all keep alives to arrive");

static int timer_set = DEFAULT_TIME;
module_param(timer_set, int, 0);
MODULE_PARM_DESC(timer_set,
                "Default Watchdog timer setting"
                "Complete cycle time"
                "The range is from 1 to 170"
                "This is the time for all keep alives to arrive");

/* After watchdog device is closed, check force_boot. If:
 * force_boot == 0, then force boot on next watchdog interrupt after close,
 * force_boot == 1, then force boot immediately when device is closed.
 */
static int force_boot;
module_param(force_boot, int, 0);
MODULE_PARM_DESC(force_boot,
                "A value of 1 means that the driver will reboot"
                "the system immediately if the /dev/watchdog device is closed"
                "A value of 0 means that when /dev/watchdog device is closed"
                "the watchdog timer will be refreshed for one more interval"
                "of length: timer_set. At the end of this interval, the"
                "watchdog timer will reset the system."
                );

/* there is only one device in the system now; this can be made into
 * an array in the future if we have more than one device */

static struct intel_scu_watchdog_dev watchdog_device;

/* Forces restart, if force_reboot is set */
static void watchdog_fire(void)
{
        if (force_boot) {
                pr_crit("Initiating system reboot\n");
                emergency_restart();
                pr_crit("Reboot didn't ?????\n");
        }

        else {
                pr_crit("Immediate Reboot Disabled\n");
                pr_crit("System will reset when watchdog timer times out!\n");
        }
}

static int check_timer_margin(int new_margin)
{
        if ((new_margin < MIN_TIME_CYCLE) ||
            (new_margin > MAX_TIME - timer_set)) {
                pr_debug("value of new_margin %d is out of the range %d to %d\n",
                         new_margin, MIN_TIME_CYCLE, MAX_TIME - timer_set);
                return -EINVAL;
        }
        return 0;
}

/*
 * IPC operations
 */
static int watchdog_set_ipc(int soft_threshold, int threshold)
{
        u32     *ipc_wbuf;
        u8       cbuf[16] = { '\0' };
        int      ipc_ret = 0;

        ipc_wbuf = (u32 *)&cbuf;
        ipc_wbuf[0] = soft_threshold;
        ipc_wbuf[1] = threshold;

        ipc_ret = intel_scu_ipc_command(
                        IPC_SET_WATCHDOG_TIMER,
                        0,
                        ipc_wbuf,
                        2,
                        NULL,
                        0);

        if (ipc_ret != 0)
                pr_err("Error setting SCU watchdog timer: %x\n", ipc_ret);

        return ipc_ret;
};

/*
 *      Intel_SCU operations
 */

/* timer interrupt handler */
static irqreturn_t watchdog_timer_interrupt(int irq, void *dev_id)
{
        int int_status;
        int_status = ioread32(watchdog_device.timer_interrupt_status_addr);

        pr_debug("irq, int_status: %x\n", int_status);

        if (int_status != 0)
                return IRQ_NONE;

        /* has the timer been started? If not, then this is spurious */
        if (watchdog_device.timer_started == 0) {
                pr_debug("spurious interrupt received\n");
                return IRQ_HANDLED;
        }

        /* temporarily disable the timer */
        iowrite32(0x00000002, watchdog_device.timer_control_addr);

        /* set the timer to the threshold */
        iowrite32(watchdog_device.threshold,
                  watchdog_device.timer_load_count_addr);

        /* allow the timer to run */
        iowrite32(0x00000003, watchdog_device.timer_control_addr);

        return IRQ_HANDLED;
}

static int intel_scu_keepalive(void)
{

        /* read eoi register - clears interrupt */
        ioread32(watchdog_device.timer_clear_interrupt_addr);

        /* temporarily disable the timer */
        iowrite32(0x00000002, watchdog_device.timer_control_addr);

        /* set the timer to the soft_threshold */
        iowrite32(watchdog_device.soft_threshold,
                  watchdog_device.timer_load_count_addr);

        /* allow the timer to run */
        iowrite32(0x00000003, watchdog_device.timer_control_addr);

        return 0;
}

static int intel_scu_stop(void)
{
        iowrite32(0, watchdog_device.timer_control_addr);
        return 0;
}

static int intel_scu_set_heartbeat(u32 t)
{
        int                      ipc_ret;
        int                      retry_count;
        u32                      soft_value;
        u32                      hw_value;

        watchdog_device.timer_set = t;
        watchdog_device.threshold =
                timer_margin * watchdog_device.timer_tbl_ptr->freq_hz;
        watchdog_device.soft_threshold =
                (watchdog_device.timer_set - timer_margin)
                * watchdog_device.timer_tbl_ptr->freq_hz;

        pr_debug("set_heartbeat: timer freq is %d\n",
                 watchdog_device.timer_tbl_ptr->freq_hz);
        pr_debug("set_heartbeat: timer_set is %x (hex)\n",
                 watchdog_device.timer_set);
        pr_debug("set_hearbeat: timer_margin is %x (hex)\n", timer_margin);
        pr_debug("set_heartbeat: threshold is %x (hex)\n",
                 watchdog_device.threshold);
        pr_debug("set_heartbeat: soft_threshold is %x (hex)\n",
                 watchdog_device.soft_threshold);

        /* Adjust thresholds by FREQ_ADJUSTMENT factor, to make the */
        /* watchdog timing come out right. */
        watchdog_device.threshold =
                watchdog_device.threshold / FREQ_ADJUSTMENT;
        watchdog_device.soft_threshold =
                watchdog_device.soft_threshold / FREQ_ADJUSTMENT;

        /* temporarily disable the timer */
        iowrite32(0x00000002, watchdog_device.timer_control_addr);

        /* send the threshold and soft_threshold via IPC to the processor */
        ipc_ret = watchdog_set_ipc(watchdog_device.soft_threshold,
                                   watchdog_device.threshold);

        if (ipc_ret != 0) {
                /* Make sure the watchdog timer is stopped */
                intel_scu_stop();
                return ipc_ret;
        }

        /* Soft Threshold set loop. Early versions of silicon did */
        /* not always set this count correctly.  This loop checks */
        /* the value and retries if it was not set correctly.     */

        retry_count = 0;
        soft_value = watchdog_device.soft_threshold & 0xFFFF0000;
        do {

                /* Make sure timer is stopped */
                intel_scu_stop();

                if (MAX_RETRY < retry_count++) {
                        /* Unable to set timer value */
                        pr_err("Unable to set timer\n");
                        return -ENODEV;
                }

                /* set the timer to the soft threshold */
                iowrite32(watchdog_device.soft_threshold,
                        watchdog_device.timer_load_count_addr);

                /* read count value before starting timer */
                ioread32(watchdog_device.timer_load_count_addr);

                /* Start the timer */
                iowrite32(0x00000003, watchdog_device.timer_control_addr);

                /* read the value the time loaded into its count reg */
                hw_value = ioread32(watchdog_device.timer_load_count_addr);
                hw_value = hw_value & 0xFFFF0000;


        } while (soft_value != hw_value);

        watchdog_device.timer_started = 1;

        return 0;
}

/*
 * /dev/watchdog handling
 */

static int intel_scu_open(struct inode *inode, struct file *file)
{

        /* Set flag to indicate that watchdog device is open */
        if (test_and_set_bit(0, &watchdog_device.driver_open))
                return -EBUSY;

        /* Check for reopen of driver. Reopens are not allowed */
        if (watchdog_device.driver_closed)
                return -EPERM;

        return nonseekable_open(inode, file);
}

static int intel_scu_release(struct inode *inode, struct file *file)
{
        /*
         * This watchdog should not be closed, after the timer
         * is started with the WDIPC_SETTIMEOUT ioctl
         * If force_boot is set watchdog_fire() will cause an
         * immediate reset. If force_boot is not set, the watchdog
         * timer is refreshed for one more interval. At the end
         * of that interval, the watchdog timer will reset the system.
         */

        if (!test_and_clear_bit(0, &watchdog_device.driver_open)) {
                pr_debug("intel_scu_release, without open\n");
                return -ENOTTY;
        }

        if (!watchdog_device.timer_started) {
                /* Just close, since timer has not been started */
                pr_debug("closed, without starting timer\n");
                return 0;
        }

        pr_crit("Unexpected close of /dev/watchdog!\n");

        /* Since the timer was started, prevent future reopens */
        watchdog_device.driver_closed = 1;

        /* Refresh the timer for one more interval */
        intel_scu_keepalive();

        /* Reboot system (if force_boot is set) */
        watchdog_fire();

        /* We should only reach this point if force_boot is not set */
        return 0;
}

static ssize_t intel_scu_write(struct file *file,
                              char const *data,
                              size_t len,
                              loff_t *ppos)
{

        if (watchdog_device.timer_started)
                /* Watchdog already started, keep it alive */
                intel_scu_keepalive();
        else
                /* Start watchdog with timer value set by init */
                intel_scu_set_heartbeat(watchdog_device.timer_set);

        return len;
}

static long intel_scu_ioctl(struct file *file,
                           unsigned int cmd,
                           unsigned long arg)
{
        void __user *argp = (void __user *)arg;
        u32 __user *p = argp;
        u32 new_margin;


        static const struct watchdog_info ident = {
                .options =          WDIOF_SETTIMEOUT
                                    | WDIOF_KEEPALIVEPING,
                .firmware_version = 0,  /* @todo Get from SCU via
                                                 ipc_get_scu_fw_version()? */
                .identity =         "Intel_SCU IOH Watchdog"  /* len < 32 */
        };

        switch (cmd) {
        case WDIOC_GETSUPPORT:
                return copy_to_user(argp,
                                    &ident,
                                    sizeof(ident)) ? -EFAULT : 0;
        case WDIOC_GETSTATUS:
        case WDIOC_GETBOOTSTATUS:
                return put_user(0, p);
        case WDIOC_KEEPALIVE:
                intel_scu_keepalive();

                return 0;
        case WDIOC_SETTIMEOUT:
                if (get_user(new_margin, p))
                        return -EFAULT;

                if (check_timer_margin(new_margin))
                        return -EINVAL;

                if (intel_scu_set_heartbeat(new_margin))
                        return -EINVAL;
                return 0;
        case WDIOC_GETTIMEOUT:
                return put_user(watchdog_device.soft_threshold, p);

        default:
                return -ENOTTY;
        }
}

/*
 *      Notifier for system down
 */
static int intel_scu_notify_sys(struct notifier_block *this,
                               unsigned long code,
                               void *another_unused)
{
        if (code == SYS_DOWN || code == SYS_HALT)
                /* Turn off the watchdog timer. */
                intel_scu_stop();
        return NOTIFY_DONE;
}

/*
 *      Kernel Interfaces
 */
static const struct file_operations intel_scu_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .write          = intel_scu_write,
        .unlocked_ioctl = intel_scu_ioctl,
        .open           = intel_scu_open,
        .release        = intel_scu_release,
};

static int __init intel_scu_watchdog_init(void)
{
        int ret;
        u32 __iomem *tmp_addr;

        /*
         * We don't really need to check this as the SFI timer get will fail
         * but if we do so we can exit with a clearer reason and no noise.
         *
         * If it isn't an intel MID device then it doesn't have this watchdog
         */
        if (!intel_mid_identify_cpu())
                return -ENODEV;

        /* Check boot parameters to verify that their initial values */
        /* are in range. */
        /* Check value of timer_set boot parameter */
        if ((timer_set < MIN_TIME_CYCLE) ||
            (timer_set > MAX_TIME - MIN_TIME_CYCLE)) {
                pr_err("value of timer_set %x (hex) is out of range from %x to %x (hex)\n",
                       timer_set, MIN_TIME_CYCLE, MAX_TIME - MIN_TIME_CYCLE);
                return -EINVAL;
        }

        /* Check value of timer_margin boot parameter */
        if (check_timer_margin(timer_margin))
                return -EINVAL;

        watchdog_device.timer_tbl_ptr = sfi_get_mtmr(sfi_mtimer_num-1);

        if (watchdog_device.timer_tbl_ptr == NULL) {
                pr_debug("timer is not available\n");
                return -ENODEV;
        }
        /* make sure the timer exists */
        if (watchdog_device.timer_tbl_ptr->phys_addr == 0) {
                pr_debug("timer %d does not have valid physical memory\n",
                         sfi_mtimer_num);
                return -ENODEV;
        }

        if (watchdog_device.timer_tbl_ptr->irq == 0) {
                pr_debug("timer %d invalid irq\n", sfi_mtimer_num);
                return -ENODEV;
        }

        tmp_addr = ioremap_nocache(watchdog_device.timer_tbl_ptr->phys_addr,
                        20);

        if (tmp_addr == NULL) {
                pr_debug("timer unable to ioremap\n");
                return -ENOMEM;
        }

        watchdog_device.timer_load_count_addr = tmp_addr++;
        watchdog_device.timer_current_value_addr = tmp_addr++;
        watchdog_device.timer_control_addr = tmp_addr++;
        watchdog_device.timer_clear_interrupt_addr = tmp_addr++;
        watchdog_device.timer_interrupt_status_addr = tmp_addr++;

        /* Set the default time values in device structure */

        watchdog_device.timer_set = timer_set;
        watchdog_device.threshold =
                timer_margin * watchdog_device.timer_tbl_ptr->freq_hz;
        watchdog_device.soft_threshold =
                (watchdog_device.timer_set - timer_margin)
                * watchdog_device.timer_tbl_ptr->freq_hz;


        watchdog_device.intel_scu_notifier.notifier_call =
                intel_scu_notify_sys;

        ret = register_reboot_notifier(&watchdog_device.intel_scu_notifier);
        if (ret) {
                pr_err("cannot register notifier %d)\n", ret);
                goto register_reboot_error;
        }

        watchdog_device.miscdev.minor = WATCHDOG_MINOR;
        watchdog_device.miscdev.name = "watchdog";
        watchdog_device.miscdev.fops = &intel_scu_fops;

        ret = misc_register(&watchdog_device.miscdev);
        if (ret) {
                pr_err("cannot register miscdev %d err =%d\n",
                       WATCHDOG_MINOR, ret);
                goto misc_register_error;
        }

        ret = request_irq((unsigned int)watchdog_device.timer_tbl_ptr->irq,
                watchdog_timer_interrupt,
                IRQF_SHARED, "watchdog",
                &watchdog_device.timer_load_count_addr);
        if (ret) {
                pr_err("error requesting irq %d\n", ret);
                goto request_irq_error;
        }
        /* Make sure timer is disabled before returning */
        intel_scu_stop();
        return 0;

/* error cleanup */

request_irq_error:
        misc_deregister(&watchdog_device.miscdev);
misc_register_error:
        unregister_reboot_notifier(&watchdog_device.intel_scu_notifier);
register_reboot_error:
        intel_scu_stop();
        iounmap(watchdog_device.timer_load_count_addr);
        return ret;
}

static void __exit intel_scu_watchdog_exit(void)
{

        misc_deregister(&watchdog_device.miscdev);
        unregister_reboot_notifier(&watchdog_device.intel_scu_notifier);
        /* disable the timer */
        iowrite32(0x00000002, watchdog_device.timer_control_addr);
        iounmap(watchdog_device.timer_load_count_addr);
}

late_initcall(intel_scu_watchdog_init);
module_exit(intel_scu_watchdog_exit);

MODULE_AUTHOR("Intel Corporation");
MODULE_DESCRIPTION("Intel SCU Watchdog Device Driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(WDT_VER);