// SPDX-License-Identifier: GPL-2.0+
/*
 * Watchdog Device Driver for Xilinx axi/xps_timebase_wdt
 *
 * (C) Copyright 2013 - 2014 Xilinx, Inc.
 * (C) Copyright 2011 (Alejandro Cabrera <aldaya@gmail.com>)
 */

#include <linux/bits.h>
#include <linux/clk.h>
#include <linux/err.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/ioport.h>
#include <linux/watchdog.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/of_address.h>

/* Register offsets for the Wdt device */
#define XWT_TWCSR0_OFFSET   0x0 /* Control/Status Register0 */
#define XWT_TWCSR1_OFFSET   0x4 /* Control/Status Register1 */
#define XWT_TBR_OFFSET      0x8 /* Timebase Register Offset */

/* Control/Status Register Masks  */
#define XWT_CSR0_WRS_MASK       BIT(3) /* Reset status */
#define XWT_CSR0_WDS_MASK       BIT(2) /* Timer state  */
#define XWT_CSR0_EWDT1_MASK     BIT(1) /* Enable bit 1 */

/* Control/Status Register 0/1 bits  */
#define XWT_CSRX_EWDT2_MASK     BIT(0) /* Enable bit 2 */

/* SelfTest constants */
#define XWT_MAX_SELFTEST_LOOP_COUNT 0x00010000
#define XWT_TIMER_FAILED            0xFFFFFFFF

#define WATCHDOG_NAME     "Xilinx Watchdog"

struct xwdt_device {
        void __iomem *base;
        u32 wdt_interval;
        spinlock_t spinlock; /* spinlock for register handling */
        struct watchdog_device xilinx_wdt_wdd;
        struct clk              *clk;
};

static int xilinx_wdt_start(struct watchdog_device *wdd)
{
        int ret;
        u32 control_status_reg;
        struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

        ret = clk_enable(xdev->clk);
        if (ret) {
                dev_err(wdd->parent, "Failed to enable clock\n");
                return ret;
        }

        spin_lock(&xdev->spinlock);

        /* Clean previous status and enable the watchdog timer */
        control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);
        control_status_reg |= (XWT_CSR0_WRS_MASK | XWT_CSR0_WDS_MASK);

        iowrite32((control_status_reg | XWT_CSR0_EWDT1_MASK),
                  xdev->base + XWT_TWCSR0_OFFSET);

        iowrite32(XWT_CSRX_EWDT2_MASK, xdev->base + XWT_TWCSR1_OFFSET);

        spin_unlock(&xdev->spinlock);

        dev_dbg(wdd->parent, "Watchdog Started!\n");

        return 0;
}

static int xilinx_wdt_stop(struct watchdog_device *wdd)
{
        u32 control_status_reg;
        struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

        spin_lock(&xdev->spinlock);

        control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);

        iowrite32((control_status_reg & ~XWT_CSR0_EWDT1_MASK),
                  xdev->base + XWT_TWCSR0_OFFSET);

        iowrite32(0, xdev->base + XWT_TWCSR1_OFFSET);

        spin_unlock(&xdev->spinlock);

        clk_disable(xdev->clk);

        dev_dbg(wdd->parent, "Watchdog Stopped!\n");

        return 0;
}

static int xilinx_wdt_keepalive(struct watchdog_device *wdd)
{
        u32 control_status_reg;
        struct xwdt_device *xdev = watchdog_get_drvdata(wdd);

        spin_lock(&xdev->spinlock);

        control_status_reg = ioread32(xdev->base + XWT_TWCSR0_OFFSET);
        control_status_reg |= (XWT_CSR0_WRS_MASK | XWT_CSR0_WDS_MASK);
        iowrite32(control_status_reg, xdev->base + XWT_TWCSR0_OFFSET);

        spin_unlock(&xdev->spinlock);

        return 0;
}

static const struct watchdog_info xilinx_wdt_ident = {
        .options =  WDIOF_MAGICCLOSE |
                    WDIOF_KEEPALIVEPING,
        .firmware_version =     1,
        .identity =     WATCHDOG_NAME,
};

static const struct watchdog_ops xilinx_wdt_ops = {
        .owner = THIS_MODULE,
        .start = xilinx_wdt_start,
        .stop = xilinx_wdt_stop,
        .ping = xilinx_wdt_keepalive,
};

static u32 xwdt_selftest(struct xwdt_device *xdev)
{
        int i;
        u32 timer_value1;
        u32 timer_value2;

        spin_lock(&xdev->spinlock);

        timer_value1 = ioread32(xdev->base + XWT_TBR_OFFSET);
        timer_value2 = ioread32(xdev->base + XWT_TBR_OFFSET);

        for (i = 0;
                ((i <= XWT_MAX_SELFTEST_LOOP_COUNT) &&
                        (timer_value2 == timer_value1)); i++) {
                timer_value2 = ioread32(xdev->base + XWT_TBR_OFFSET);
        }

        spin_unlock(&xdev->spinlock);

        if (timer_value2 != timer_value1)
                return ~XWT_TIMER_FAILED;
        else
                return XWT_TIMER_FAILED;
}

static void xwdt_clk_disable_unprepare(void *data)
{
        clk_disable_unprepare(data);
}

static int xwdt_probe(struct platform_device *pdev)
{
        struct device *dev = &pdev->dev;
        int rc;
        u32 pfreq = 0, enable_once = 0;
        struct xwdt_device *xdev;
        struct watchdog_device *xilinx_wdt_wdd;

        xdev = devm_kzalloc(dev, sizeof(*xdev), GFP_KERNEL);
        if (!xdev)
                return -ENOMEM;

        xilinx_wdt_wdd = &xdev->xilinx_wdt_wdd;
        xilinx_wdt_wdd->info = &xilinx_wdt_ident;
        xilinx_wdt_wdd->ops = &xilinx_wdt_ops;
        xilinx_wdt_wdd->parent = dev;

        xdev->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(xdev->base))
                return PTR_ERR(xdev->base);

        rc = of_property_read_u32(dev->of_node, "xlnx,wdt-interval",
                                  &xdev->wdt_interval);
        if (rc)
                dev_warn(dev, "Parameter \"xlnx,wdt-interval\" not found\n");

        rc = of_property_read_u32(dev->of_node, "xlnx,wdt-enable-once",
                                  &enable_once);
        if (rc)
                dev_warn(dev,
                         "Parameter \"xlnx,wdt-enable-once\" not found\n");

        watchdog_set_nowayout(xilinx_wdt_wdd, enable_once);

        xdev->clk = devm_clk_get(dev, NULL);
        if (IS_ERR(xdev->clk)) {
                if (PTR_ERR(xdev->clk) != -ENOENT)
                        return PTR_ERR(xdev->clk);

                /*
                 * Clock framework support is optional, continue on
                 * anyways if we don't find a matching clock.
                 */
                xdev->clk = NULL;

                rc = of_property_read_u32(dev->of_node, "clock-frequency",
                                          &pfreq);
                if (rc)
                        dev_warn(dev,
                                 "The watchdog clock freq cannot be obtained\n");
        } else {
                pfreq = clk_get_rate(xdev->clk);
                rc = clk_prepare_enable(xdev->clk);
                if (rc) {
                        dev_err(dev, "unable to enable clock\n");
                        return rc;
                }
                rc = devm_add_action_or_reset(dev, xwdt_clk_disable_unprepare,
                                              xdev->clk);
                if (rc)
                        return rc;
        }

        /*
         * Twice of the 2^wdt_interval / freq  because the first wdt overflow is
         * ignored (interrupt), reset is only generated at second wdt overflow
         */
        if (pfreq && xdev->wdt_interval)
                xilinx_wdt_wdd->timeout = 2 * ((1 << xdev->wdt_interval) /
                                          pfreq);

        spin_lock_init(&xdev->spinlock);
        watchdog_set_drvdata(xilinx_wdt_wdd, xdev);

        rc = xwdt_selftest(xdev);
        if (rc == XWT_TIMER_FAILED) {
                dev_err(dev, "SelfTest routine error\n");
                return rc;
        }

        rc = devm_watchdog_register_device(dev, xilinx_wdt_wdd);
        if (rc)
                return rc;

        clk_disable(xdev->clk);

        dev_info(dev, "Xilinx Watchdog Timer with timeout %ds\n",
                 xilinx_wdt_wdd->timeout);

        platform_set_drvdata(pdev, xdev);

        return 0;
}

/**
 * xwdt_suspend - Suspend the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 always.
 */
static int __maybe_unused xwdt_suspend(struct device *dev)
{
        struct xwdt_device *xdev = dev_get_drvdata(dev);

        if (watchdog_active(&xdev->xilinx_wdt_wdd))
                xilinx_wdt_stop(&xdev->xilinx_wdt_wdd);

        return 0;
}

/**
 * xwdt_resume - Resume the device.
 *
 * @dev: handle to the device structure.
 * Return: 0 on success, errno otherwise.
 */
static int __maybe_unused xwdt_resume(struct device *dev)
{
        struct xwdt_device *xdev = dev_get_drvdata(dev);
        int ret = 0;

        if (watchdog_active(&xdev->xilinx_wdt_wdd))
                ret = xilinx_wdt_start(&xdev->xilinx_wdt_wdd);

        return ret;
}

static SIMPLE_DEV_PM_OPS(xwdt_pm_ops, xwdt_suspend, xwdt_resume);

/* Match table for of_platform binding */
static const struct of_device_id xwdt_of_match[] = {
        { .compatible = "xlnx,xps-timebase-wdt-1.00.a", },
        { .compatible = "xlnx,xps-timebase-wdt-1.01.a", },
        {},
};
MODULE_DEVICE_TABLE(of, xwdt_of_match);

static struct platform_driver xwdt_driver = {
        .probe       = xwdt_probe,
        .driver = {
                .name  = WATCHDOG_NAME,
                .of_match_table = xwdt_of_match,
                .pm = &xwdt_pm_ops,
        },
};

module_platform_driver(xwdt_driver);

MODULE_AUTHOR("Alejandro Cabrera <aldaya@gmail.com>");
MODULE_DESCRIPTION("Xilinx Watchdog driver");
MODULE_LICENSE("GPL");