/*
 * Watchdog timer for PowerPC Book-E systems
 *
 * Author: Matthew McClintock
 * Maintainer: Kumar Gala <galak@kernel.crashing.org>
 *
 * Copyright 2005, 2008, 2010-2011 Freescale Semiconductor Inc.
 *
 * This program is free software; you can redistribute  it and/or modify it
 * under  the terms of  the GNU General  Public License as published by the
 * Free Software Foundation;  either version 2 of the  License, or (at your
 * option) any later version.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/smp.h>
#include <linux/watchdog.h>

#include <asm/reg_booke.h>
#include <asm/time.h>
#include <asm/div64.h>

/* If the kernel parameter wdt=1, the watchdog will be enabled at boot.
 * Also, the wdt_period sets the watchdog timer period timeout.
 * For E500 cpus the wdt_period sets which bit changing from 0->1 will
 * trigger a watchog timeout. This watchdog timeout will occur 3 times, the
 * first time nothing will happen, the second time a watchdog exception will
 * occur, and the final time the board will reset.
 */


#ifdef  CONFIG_PPC_FSL_BOOK3E
#define WDTP(x)         ((((x)&0x3)<<30)|(((x)&0x3c)<<15))
#define WDTP_MASK       (WDTP(0x3f))
#else
#define WDTP(x)         (TCR_WP(x))
#define WDTP_MASK       (TCR_WP_MASK)
#endif

static bool booke_wdt_enabled;
module_param(booke_wdt_enabled, bool, 0);
static int  booke_wdt_period = CONFIG_BOOKE_WDT_DEFAULT_TIMEOUT;
module_param(booke_wdt_period, int, 0);

#ifdef CONFIG_PPC_FSL_BOOK3E

/* For the specified period, determine the number of seconds
 * corresponding to the reset time.  There will be a watchdog
 * exception at approximately 3/5 of this time.
 *
 * The formula to calculate this is given by:
 * 2.5 * (2^(63-period+1)) / timebase_freq
 *
 * In order to simplify things, we assume that period is
 * at least 1.  This will still result in a very long timeout.
 */
static unsigned long long period_to_sec(unsigned int period)
{
        unsigned long long tmp = 1ULL << (64 - period);
        unsigned long tmp2 = ppc_tb_freq;

        /* tmp may be a very large number and we don't want to overflow,
         * so divide the timebase freq instead of multiplying tmp
         */
        tmp2 = tmp2 / 5 * 2;

        do_div(tmp, tmp2);
        return tmp;
}

/*
 * This procedure will find the highest period which will give a timeout
 * greater than the one required. e.g. for a bus speed of 66666666 and
 * and a parameter of 2 secs, then this procedure will return a value of 38.
 */
static unsigned int sec_to_period(unsigned int secs)
{
        unsigned int period;
        for (period = 63; period > 0; period--) {
                if (period_to_sec(period) >= secs)
                        return period;
        }
        return 0;
}

#define MAX_WDT_TIMEOUT         period_to_sec(1)

#else /* CONFIG_PPC_FSL_BOOK3E */

static unsigned long long period_to_sec(unsigned int period)
{
        return period;
}

static unsigned int sec_to_period(unsigned int secs)
{
        return secs;
}

#define MAX_WDT_TIMEOUT         3       /* from Kconfig */

#endif /* !CONFIG_PPC_FSL_BOOK3E */

static void __booke_wdt_set(void *data)
{
        u32 val;
        struct watchdog_device *wdog = data;

        val = mfspr(SPRN_TCR);
        val &= ~WDTP_MASK;
        val |= WDTP(sec_to_period(wdog->timeout));

        mtspr(SPRN_TCR, val);
}

static void booke_wdt_set(void *data)
{
        on_each_cpu(__booke_wdt_set, data, 0);
}

static void __booke_wdt_ping(void *data)
{
        mtspr(SPRN_TSR, TSR_ENW|TSR_WIS);
}

static int booke_wdt_ping(struct watchdog_device *wdog)
{
        on_each_cpu(__booke_wdt_ping, NULL, 0);

        return 0;
}

static void __booke_wdt_enable(void *data)
{
        u32 val;
        struct watchdog_device *wdog = data;

        /* clear status before enabling watchdog */
        __booke_wdt_ping(NULL);
        val = mfspr(SPRN_TCR);
        val &= ~WDTP_MASK;
        val |= (TCR_WIE|TCR_WRC(WRC_CHIP)|WDTP(sec_to_period(wdog->timeout)));

        mtspr(SPRN_TCR, val);
}

/**
 * booke_wdt_disable - disable the watchdog on the given CPU
 *
 * This function is called on each CPU.  It disables the watchdog on that CPU.
 *
 * TCR[WRC] cannot be changed once it has been set to non-zero, but we can
 * effectively disable the watchdog by setting its period to the maximum value.
 */
static void __booke_wdt_disable(void *data)
{
        u32 val;

        val = mfspr(SPRN_TCR);
        val &= ~(TCR_WIE | WDTP_MASK);
        mtspr(SPRN_TCR, val);

        /* clear status to make sure nothing is pending */
        __booke_wdt_ping(NULL);

}

static int booke_wdt_start(struct watchdog_device *wdog)
{
        on_each_cpu(__booke_wdt_enable, wdog, 0);
        pr_debug("watchdog enabled (timeout = %u sec)\n", wdog->timeout);

        return 0;
}

static int booke_wdt_stop(struct watchdog_device *wdog)
{
        on_each_cpu(__booke_wdt_disable, NULL, 0);
        pr_debug("watchdog disabled\n");

        return 0;
}

static int booke_wdt_set_timeout(struct watchdog_device *wdt_dev,
                                 unsigned int timeout)
{
        wdt_dev->timeout = timeout;
        booke_wdt_set(wdt_dev);

        return 0;
}

static struct watchdog_info booke_wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
        .identity = "PowerPC Book-E Watchdog",
};

static struct watchdog_ops booke_wdt_ops = {
        .owner = THIS_MODULE,
        .start = booke_wdt_start,
        .stop = booke_wdt_stop,
        .ping = booke_wdt_ping,
        .set_timeout = booke_wdt_set_timeout,
};

static struct watchdog_device booke_wdt_dev = {
        .info = &booke_wdt_info,
        .ops = &booke_wdt_ops,
        .min_timeout = 1,
};

static void __exit booke_wdt_exit(void)
{
        watchdog_unregister_device(&booke_wdt_dev);
}

static int __init booke_wdt_init(void)
{
        int ret = 0;
        bool nowayout = WATCHDOG_NOWAYOUT;

        pr_info("powerpc book-e watchdog driver loaded\n");
        booke_wdt_info.firmware_version = cur_cpu_spec->pvr_value;
        booke_wdt_set_timeout(&booke_wdt_dev,
                              period_to_sec(booke_wdt_period));
        watchdog_set_nowayout(&booke_wdt_dev, nowayout);
        booke_wdt_dev.max_timeout = MAX_WDT_TIMEOUT;
        if (booke_wdt_enabled)
                booke_wdt_start(&booke_wdt_dev);

        ret = watchdog_register_device(&booke_wdt_dev);

        return ret;
}

module_init(booke_wdt_init);
module_exit(booke_wdt_exit);

MODULE_ALIAS("booke_wdt");
MODULE_DESCRIPTION("PowerPC Book-E watchdog driver");
MODULE_LICENSE("GPL");