/*
 * Cadence WDT driver - Used by Xilinx Zynq
 *
 * Copyright (C) 2010 - 2014 Xilinx, 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.
 */

#include <linux/clk.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/irq.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

#define CDNS_WDT_DEFAULT_TIMEOUT        10
/* Supports 1 - 516 sec */
#define CDNS_WDT_MIN_TIMEOUT    1
#define CDNS_WDT_MAX_TIMEOUT    516

/* Restart key */
#define CDNS_WDT_RESTART_KEY 0x00001999

/* Counter register access key */
#define CDNS_WDT_REGISTER_ACCESS_KEY 0x00920000

/* Counter value divisor */
#define CDNS_WDT_COUNTER_VALUE_DIVISOR 0x1000

/* Clock prescaler value and selection */
#define CDNS_WDT_PRESCALE_64    64
#define CDNS_WDT_PRESCALE_512   512
#define CDNS_WDT_PRESCALE_4096  4096
#define CDNS_WDT_PRESCALE_SELECT_64     1
#define CDNS_WDT_PRESCALE_SELECT_512    2
#define CDNS_WDT_PRESCALE_SELECT_4096   3

/* Input clock frequency */
#define CDNS_WDT_CLK_10MHZ      10000000
#define CDNS_WDT_CLK_75MHZ      75000000

/* Counter maximum value */
#define CDNS_WDT_COUNTER_MAX 0xFFF

static int wdt_timeout = CDNS_WDT_DEFAULT_TIMEOUT;
static int nowayout = WATCHDOG_NOWAYOUT;

module_param(wdt_timeout, int, 0);
MODULE_PARM_DESC(wdt_timeout,
                 "Watchdog time in seconds. (default="
                 __MODULE_STRING(CDNS_WDT_DEFAULT_TIMEOUT) ")");

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

/**
 * struct cdns_wdt - Watchdog device structure
 * @regs: baseaddress of device
 * @rst: reset flag
 * @clk: struct clk * of a clock source
 * @prescaler: for saving prescaler value
 * @ctrl_clksel: counter clock prescaler selection
 * @io_lock: spinlock for IO register access
 * @cdns_wdt_device: watchdog device structure
 *
 * Structure containing parameters specific to cadence watchdog.
 */
struct cdns_wdt {
        void __iomem            *regs;
        bool                    rst;
        struct clk              *clk;
        u32                     prescaler;
        u32                     ctrl_clksel;
        spinlock_t              io_lock;
        struct watchdog_device  cdns_wdt_device;
};

/* Write access to Registers */
static inline void cdns_wdt_writereg(struct cdns_wdt *wdt, u32 offset, u32 val)
{
        writel_relaxed(val, wdt->regs + offset);
}

/*************************Register Map**************************************/

/* Register Offsets for the WDT */
#define CDNS_WDT_ZMR_OFFSET     0x0     /* Zero Mode Register */
#define CDNS_WDT_CCR_OFFSET     0x4     /* Counter Control Register */
#define CDNS_WDT_RESTART_OFFSET 0x8     /* Restart Register */
#define CDNS_WDT_SR_OFFSET      0xC     /* Status Register */

/*
 * Zero Mode Register - This register controls how the time out is indicated
 * and also contains the access code to allow writes to the register (0xABC).
 */
#define CDNS_WDT_ZMR_WDEN_MASK  0x00000001 /* Enable the WDT */
#define CDNS_WDT_ZMR_RSTEN_MASK 0x00000002 /* Enable the reset output */
#define CDNS_WDT_ZMR_IRQEN_MASK 0x00000004 /* Enable IRQ output */
#define CDNS_WDT_ZMR_RSTLEN_16  0x00000030 /* Reset pulse of 16 pclk cycles */
#define CDNS_WDT_ZMR_ZKEY_VAL   0x00ABC000 /* Access key, 0xABC << 12 */
/*
 * Counter Control register - This register controls how fast the timer runs
 * and the reset value and also contains the access code to allow writes to
 * the register.
 */
#define CDNS_WDT_CCR_CRV_MASK   0x00003FFC /* Counter reset value */

/**
 * cdns_wdt_stop - Stop the watchdog.
 *
 * @wdd: watchdog device
 *
 * Read the contents of the ZMR register, clear the WDEN bit
 * in the register and set the access key for successful write.
 *
 * Return: always 0
 */
static int cdns_wdt_stop(struct watchdog_device *wdd)
{
        struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

        spin_lock(&wdt->io_lock);
        cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
                          CDNS_WDT_ZMR_ZKEY_VAL & (~CDNS_WDT_ZMR_WDEN_MASK));
        spin_unlock(&wdt->io_lock);

        return 0;
}

/**
 * cdns_wdt_reload - Reload the watchdog timer (i.e. pat the watchdog).
 *
 * @wdd: watchdog device
 *
 * Write the restart key value (0x00001999) to the restart register.
 *
 * Return: always 0
 */
static int cdns_wdt_reload(struct watchdog_device *wdd)
{
        struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);

        spin_lock(&wdt->io_lock);
        cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
                          CDNS_WDT_RESTART_KEY);
        spin_unlock(&wdt->io_lock);

        return 0;
}

/**
 * cdns_wdt_start - Enable and start the watchdog.
 *
 * @wdd: watchdog device
 *
 * The counter value is calculated according to the formula:
 *              calculated count = (timeout * clock) / prescaler + 1.
 * The calculated count is divided by 0x1000 to obtain the field value
 * to write to counter control register.
 * Clears the contents of prescaler and counter reset value. Sets the
 * prescaler to 4096 and the calculated count and access key
 * to write to CCR Register.
 * Sets the WDT (WDEN bit) and either the Reset signal(RSTEN bit)
 * or Interrupt signal(IRQEN) with a specified cycles and the access
 * key to write to ZMR Register.
 *
 * Return: always 0
 */
static int cdns_wdt_start(struct watchdog_device *wdd)
{
        struct cdns_wdt *wdt = watchdog_get_drvdata(wdd);
        unsigned int data = 0;
        unsigned short count;
        unsigned long clock_f = clk_get_rate(wdt->clk);

        /*
         * Counter value divisor to obtain the value of
         * counter reset to be written to control register.
         */
        count = (wdd->timeout * (clock_f / wdt->prescaler)) /
                 CDNS_WDT_COUNTER_VALUE_DIVISOR + 1;

        if (count > CDNS_WDT_COUNTER_MAX)
                count = CDNS_WDT_COUNTER_MAX;

        spin_lock(&wdt->io_lock);
        cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET,
                          CDNS_WDT_ZMR_ZKEY_VAL);

        count = (count << 2) & CDNS_WDT_CCR_CRV_MASK;

        /* Write counter access key first to be able write to register */
        data = count | CDNS_WDT_REGISTER_ACCESS_KEY | wdt->ctrl_clksel;
        cdns_wdt_writereg(wdt, CDNS_WDT_CCR_OFFSET, data);
        data = CDNS_WDT_ZMR_WDEN_MASK | CDNS_WDT_ZMR_RSTLEN_16 |
               CDNS_WDT_ZMR_ZKEY_VAL;

        /* Reset on timeout if specified in device tree. */
        if (wdt->rst) {
                data |= CDNS_WDT_ZMR_RSTEN_MASK;
                data &= ~CDNS_WDT_ZMR_IRQEN_MASK;
        } else {
                data &= ~CDNS_WDT_ZMR_RSTEN_MASK;
                data |= CDNS_WDT_ZMR_IRQEN_MASK;
        }
        cdns_wdt_writereg(wdt, CDNS_WDT_ZMR_OFFSET, data);
        cdns_wdt_writereg(wdt, CDNS_WDT_RESTART_OFFSET,
                          CDNS_WDT_RESTART_KEY);
        spin_unlock(&wdt->io_lock);

        return 0;
}

/**
 * cdns_wdt_settimeout - Set a new timeout value for the watchdog device.
 *
 * @wdd: watchdog device
 * @new_time: new timeout value that needs to be set
 * Return: 0 on success
 *
 * Update the watchdog_device timeout with new value which is used when
 * cdns_wdt_start is called.
 */
static int cdns_wdt_settimeout(struct watchdog_device *wdd,
                               unsigned int new_time)
{
        wdd->timeout = new_time;

        return cdns_wdt_start(wdd);
}

/**
 * cdns_wdt_irq_handler - Notifies of watchdog timeout.
 *
 * @irq: interrupt number
 * @dev_id: pointer to a platform device structure
 * Return: IRQ_HANDLED
 *
 * The handler is invoked when the watchdog times out and a
 * reset on timeout has not been enabled.
 */
static irqreturn_t cdns_wdt_irq_handler(int irq, void *dev_id)
{
        struct platform_device *pdev = dev_id;

        dev_info(&pdev->dev,
                 "Watchdog timed out. Internal reset not enabled\n");

        return IRQ_HANDLED;
}

/*
 * Info structure used to indicate the features supported by the device
 * to the upper layers. This is defined in watchdog.h header file.
 */
static struct watchdog_info cdns_wdt_info = {
        .identity       = "cdns_wdt watchdog",
        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
                          WDIOF_MAGICCLOSE,
};

/* Watchdog Core Ops */
static struct watchdog_ops cdns_wdt_ops = {
        .owner = THIS_MODULE,
        .start = cdns_wdt_start,
        .stop = cdns_wdt_stop,
        .ping = cdns_wdt_reload,
        .set_timeout = cdns_wdt_settimeout,
};

/************************Platform Operations*****************************/
/**
 * cdns_wdt_probe - Probe call for the device.
 *
 * @pdev: handle to the platform device structure.
 * Return: 0 on success, negative error otherwise.
 *
 * It does all the memory allocation and registration for the device.
 */
static int cdns_wdt_probe(struct platform_device *pdev)
{
        struct resource *res;
        int ret, irq;
        unsigned long clock_f;
        struct cdns_wdt *wdt;
        struct watchdog_device *cdns_wdt_device;

        wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
        if (!wdt)
                return -ENOMEM;

        cdns_wdt_device = &wdt->cdns_wdt_device;
        cdns_wdt_device->info = &cdns_wdt_info;
        cdns_wdt_device->ops = &cdns_wdt_ops;
        cdns_wdt_device->timeout = CDNS_WDT_DEFAULT_TIMEOUT;
        cdns_wdt_device->min_timeout = CDNS_WDT_MIN_TIMEOUT;
        cdns_wdt_device->max_timeout = CDNS_WDT_MAX_TIMEOUT;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        wdt->regs = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(wdt->regs))
                return PTR_ERR(wdt->regs);

        /* Register the interrupt */
        wdt->rst = of_property_read_bool(pdev->dev.of_node, "reset-on-timeout");
        irq = platform_get_irq(pdev, 0);
        if (!wdt->rst && irq >= 0) {
                ret = devm_request_irq(&pdev->dev, irq, cdns_wdt_irq_handler, 0,
                                       pdev->name, pdev);
                if (ret) {
                        dev_err(&pdev->dev,
                                "cannot register interrupt handler err=%d\n",
                                ret);
                        return ret;
                }
        }

        /* Initialize the members of cdns_wdt structure */
        cdns_wdt_device->parent = &pdev->dev;

        ret = watchdog_init_timeout(cdns_wdt_device, wdt_timeout, &pdev->dev);
        if (ret) {
                dev_err(&pdev->dev, "unable to set timeout value\n");
                return ret;
        }

        watchdog_set_nowayout(cdns_wdt_device, nowayout);
        watchdog_stop_on_reboot(cdns_wdt_device);
        watchdog_set_drvdata(cdns_wdt_device, wdt);

        wdt->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(wdt->clk)) {
                dev_err(&pdev->dev, "input clock not found\n");
                ret = PTR_ERR(wdt->clk);
                return ret;
        }

        ret = clk_prepare_enable(wdt->clk);
        if (ret) {
                dev_err(&pdev->dev, "unable to enable clock\n");
                return ret;
        }

        clock_f = clk_get_rate(wdt->clk);
        if (clock_f <= CDNS_WDT_CLK_75MHZ) {
                wdt->prescaler = CDNS_WDT_PRESCALE_512;
                wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_512;
        } else {
                wdt->prescaler = CDNS_WDT_PRESCALE_4096;
                wdt->ctrl_clksel = CDNS_WDT_PRESCALE_SELECT_4096;
        }

        spin_lock_init(&wdt->io_lock);

        ret = watchdog_register_device(cdns_wdt_device);
        if (ret) {
                dev_err(&pdev->dev, "Failed to register wdt device\n");
                goto err_clk_disable;
        }
        platform_set_drvdata(pdev, wdt);

        dev_dbg(&pdev->dev, "Xilinx Watchdog Timer at %p with timeout %ds%s\n",
                 wdt->regs, cdns_wdt_device->timeout,
                 nowayout ? ", nowayout" : "");

        return 0;

err_clk_disable:
        clk_disable_unprepare(wdt->clk);

        return ret;
}

/**
 * cdns_wdt_remove - Probe call for the device.
 *
 * @pdev: handle to the platform device structure.
 * Return: 0 on success, otherwise negative error.
 *
 * Unregister the device after releasing the resources.
 */
static int cdns_wdt_remove(struct platform_device *pdev)
{
        struct cdns_wdt *wdt = platform_get_drvdata(pdev);

        cdns_wdt_stop(&wdt->cdns_wdt_device);
        watchdog_unregister_device(&wdt->cdns_wdt_device);
        clk_disable_unprepare(wdt->clk);

        return 0;
}

/**
 * cdns_wdt_shutdown - Stop the device.
 *
 * @pdev: handle to the platform structure.
 *
 */
static void cdns_wdt_shutdown(struct platform_device *pdev)
{
        struct cdns_wdt *wdt = platform_get_drvdata(pdev);

        cdns_wdt_stop(&wdt->cdns_wdt_device);
        clk_disable_unprepare(wdt->clk);
}

/**
 * cdns_wdt_suspend - Stop the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 always.
 */
static int __maybe_unused cdns_wdt_suspend(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct cdns_wdt *wdt = platform_get_drvdata(pdev);

        cdns_wdt_stop(&wdt->cdns_wdt_device);
        clk_disable_unprepare(wdt->clk);

        return 0;
}

/**
 * cdns_wdt_resume - Resume the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 on success, errno otherwise.
 */
static int __maybe_unused cdns_wdt_resume(struct device *dev)
{
        int ret;
        struct platform_device *pdev = to_platform_device(dev);
        struct cdns_wdt *wdt = platform_get_drvdata(pdev);

        ret = clk_prepare_enable(wdt->clk);
        if (ret) {
                dev_err(dev, "unable to enable clock\n");
                return ret;
        }
        cdns_wdt_start(&wdt->cdns_wdt_device);

        return 0;
}

static SIMPLE_DEV_PM_OPS(cdns_wdt_pm_ops, cdns_wdt_suspend, cdns_wdt_resume);

static struct of_device_id cdns_wdt_of_match[] = {
        { .compatible = "cdns,wdt-r1p2", },
        { /* end of table */ }
};
MODULE_DEVICE_TABLE(of, cdns_wdt_of_match);

/* Driver Structure */
static struct platform_driver cdns_wdt_driver = {
        .probe          = cdns_wdt_probe,
        .remove         = cdns_wdt_remove,
        .shutdown       = cdns_wdt_shutdown,
        .driver         = {
                .name   = "cdns-wdt",
                .of_match_table = cdns_wdt_of_match,
                .pm     = &cdns_wdt_pm_ops,
        },
};

module_platform_driver(cdns_wdt_driver);

MODULE_AUTHOR("Xilinx, Inc.");
MODULE_DESCRIPTION("Watchdog driver for Cadence WDT");
MODULE_LICENSE("GPL");