/*
 * Copyright 2016 IBM Corporation
 *
 * Joel Stanley <joel@jms.id.au>
 *
 * 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/delay.h>
#include <linux/io.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/watchdog.h>

struct aspeed_wdt {
        struct watchdog_device  wdd;
        void __iomem            *base;
        u32                     ctrl;
};

struct aspeed_wdt_config {
        u32 ext_pulse_width_mask;
};

static const struct aspeed_wdt_config ast2400_config = {
        .ext_pulse_width_mask = 0xff,
};

static const struct aspeed_wdt_config ast2500_config = {
        .ext_pulse_width_mask = 0xfffff,
};

static const struct of_device_id aspeed_wdt_of_table[] = {
        { .compatible = "aspeed,ast2400-wdt", .data = &ast2400_config },
        { .compatible = "aspeed,ast2500-wdt", .data = &ast2500_config },
        { },
};
MODULE_DEVICE_TABLE(of, aspeed_wdt_of_table);

#define WDT_STATUS              0x00
#define WDT_RELOAD_VALUE        0x04
#define WDT_RESTART             0x08
#define WDT_CTRL                0x0C
#define   WDT_CTRL_BOOT_SECONDARY       BIT(7)
#define   WDT_CTRL_RESET_MODE_SOC       (0x00 << 5)
#define   WDT_CTRL_RESET_MODE_FULL_CHIP (0x01 << 5)
#define   WDT_CTRL_RESET_MODE_ARM_CPU   (0x10 << 5)
#define   WDT_CTRL_1MHZ_CLK             BIT(4)
#define   WDT_CTRL_WDT_EXT              BIT(3)
#define   WDT_CTRL_WDT_INTR             BIT(2)
#define   WDT_CTRL_RESET_SYSTEM         BIT(1)
#define   WDT_CTRL_ENABLE               BIT(0)
#define WDT_TIMEOUT_STATUS      0x10
#define   WDT_TIMEOUT_STATUS_BOOT_SECONDARY     BIT(1)

/*
 * WDT_RESET_WIDTH controls the characteristics of the external pulse (if
 * enabled), specifically:
 *
 * * Pulse duration
 * * Drive mode: push-pull vs open-drain
 * * Polarity: Active high or active low
 *
 * Pulse duration configuration is available on both the AST2400 and AST2500,
 * though the field changes between SoCs:
 *
 * AST2400: Bits 7:0
 * AST2500: Bits 19:0
 *
 * This difference is captured in struct aspeed_wdt_config.
 *
 * The AST2500 exposes the drive mode and polarity options, but not in a
 * regular fashion. For read purposes, bit 31 represents active high or low,
 * and bit 30 represents push-pull or open-drain. With respect to write, magic
 * values need to be written to the top byte to change the state of the drive
 * mode and polarity bits. Any other value written to the top byte has no
 * effect on the state of the drive mode or polarity bits. However, the pulse
 * width value must be preserved (as desired) if written.
 */
#define WDT_RESET_WIDTH         0x18
#define   WDT_RESET_WIDTH_ACTIVE_HIGH   BIT(31)
#define     WDT_ACTIVE_HIGH_MAGIC       (0xA5 << 24)
#define     WDT_ACTIVE_LOW_MAGIC        (0x5A << 24)
#define   WDT_RESET_WIDTH_PUSH_PULL     BIT(30)
#define     WDT_PUSH_PULL_MAGIC         (0xA8 << 24)
#define     WDT_OPEN_DRAIN_MAGIC        (0x8A << 24)

#define WDT_RESTART_MAGIC       0x4755

/* 32 bits at 1MHz, in milliseconds */
#define WDT_MAX_TIMEOUT_MS      4294967
#define WDT_DEFAULT_TIMEOUT     30
#define WDT_RATE_1MHZ           1000000

static struct aspeed_wdt *to_aspeed_wdt(struct watchdog_device *wdd)
{
        return container_of(wdd, struct aspeed_wdt, wdd);
}

static void aspeed_wdt_enable(struct aspeed_wdt *wdt, int count)
{
        wdt->ctrl |= WDT_CTRL_ENABLE;

        writel(0, wdt->base + WDT_CTRL);
        writel(count, wdt->base + WDT_RELOAD_VALUE);
        writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);
        writel(wdt->ctrl, wdt->base + WDT_CTRL);
}

static int aspeed_wdt_start(struct watchdog_device *wdd)
{
        struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

        aspeed_wdt_enable(wdt, wdd->timeout * WDT_RATE_1MHZ);

        return 0;
}

static int aspeed_wdt_stop(struct watchdog_device *wdd)
{
        struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

        wdt->ctrl &= ~WDT_CTRL_ENABLE;
        writel(wdt->ctrl, wdt->base + WDT_CTRL);

        return 0;
}

static int aspeed_wdt_ping(struct watchdog_device *wdd)
{
        struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

        writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

        return 0;
}

static int aspeed_wdt_set_timeout(struct watchdog_device *wdd,
                                  unsigned int timeout)
{
        struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);
        u32 actual;

        wdd->timeout = timeout;

        actual = min(timeout, wdd->max_hw_heartbeat_ms * 1000);

        writel(actual * WDT_RATE_1MHZ, wdt->base + WDT_RELOAD_VALUE);
        writel(WDT_RESTART_MAGIC, wdt->base + WDT_RESTART);

        return 0;
}

static int aspeed_wdt_restart(struct watchdog_device *wdd,
                              unsigned long action, void *data)
{
        struct aspeed_wdt *wdt = to_aspeed_wdt(wdd);

        wdt->ctrl &= ~WDT_CTRL_BOOT_SECONDARY;
        aspeed_wdt_enable(wdt, 128 * WDT_RATE_1MHZ / 1000);

        mdelay(1000);

        return 0;
}

static const struct watchdog_ops aspeed_wdt_ops = {
        .start          = aspeed_wdt_start,
        .stop           = aspeed_wdt_stop,
        .ping           = aspeed_wdt_ping,
        .set_timeout    = aspeed_wdt_set_timeout,
        .restart        = aspeed_wdt_restart,
        .owner          = THIS_MODULE,
};

static const struct watchdog_info aspeed_wdt_info = {
        .options        = WDIOF_KEEPALIVEPING
                        | WDIOF_MAGICCLOSE
                        | WDIOF_SETTIMEOUT,
        .identity       = KBUILD_MODNAME,
};

static int aspeed_wdt_probe(struct platform_device *pdev)
{
        const struct aspeed_wdt_config *config;
        const struct of_device_id *ofdid;
        struct aspeed_wdt *wdt;
        struct resource *res;
        struct device_node *np;
        const char *reset_type;
        u32 duration;
        u32 status;
        int ret;

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

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

        /*
         * The ast2400 wdt can run at PCLK, or 1MHz. The ast2500 only
         * runs at 1MHz. We chose to always run at 1MHz, as there's no
         * good reason to have a faster watchdog counter.
         */
        wdt->wdd.info = &aspeed_wdt_info;
        wdt->wdd.ops = &aspeed_wdt_ops;
        wdt->wdd.max_hw_heartbeat_ms = WDT_MAX_TIMEOUT_MS;
        wdt->wdd.parent = &pdev->dev;

        wdt->wdd.timeout = WDT_DEFAULT_TIMEOUT;
        watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev);

        np = pdev->dev.of_node;

        ofdid = of_match_node(aspeed_wdt_of_table, np);
        if (!ofdid)
                return -EINVAL;
        config = ofdid->data;

        wdt->ctrl = WDT_CTRL_1MHZ_CLK;

        /*
         * Control reset on a per-device basis to ensure the
         * host is not affected by a BMC reboot
         */
        ret = of_property_read_string(np, "aspeed,reset-type", &reset_type);
        if (ret) {
                wdt->ctrl |= WDT_CTRL_RESET_MODE_SOC | WDT_CTRL_RESET_SYSTEM;
        } else {
                if (!strcmp(reset_type, "cpu"))
                        wdt->ctrl |= WDT_CTRL_RESET_MODE_ARM_CPU |
                                     WDT_CTRL_RESET_SYSTEM;
                else if (!strcmp(reset_type, "soc"))
                        wdt->ctrl |= WDT_CTRL_RESET_MODE_SOC |
                                     WDT_CTRL_RESET_SYSTEM;
                else if (!strcmp(reset_type, "system"))
                        wdt->ctrl |= WDT_CTRL_RESET_MODE_FULL_CHIP |
                                     WDT_CTRL_RESET_SYSTEM;
                else if (strcmp(reset_type, "none"))
                        return -EINVAL;
        }
        if (of_property_read_bool(np, "aspeed,external-signal"))
                wdt->ctrl |= WDT_CTRL_WDT_EXT;
        if (of_property_read_bool(np, "aspeed,alt-boot"))
                wdt->ctrl |= WDT_CTRL_BOOT_SECONDARY;

        if (readl(wdt->base + WDT_CTRL) & WDT_CTRL_ENABLE)  {
                /*
                 * The watchdog is running, but invoke aspeed_wdt_start() to
                 * write wdt->ctrl to WDT_CTRL to ensure the watchdog's
                 * configuration conforms to the driver's expectations.
                 * Primarily, ensure we're using the 1MHz clock source.
                 */
                aspeed_wdt_start(&wdt->wdd);
                set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
        }

        if (of_device_is_compatible(np, "aspeed,ast2500-wdt")) {
                u32 reg = readl(wdt->base + WDT_RESET_WIDTH);

                reg &= config->ext_pulse_width_mask;
                if (of_property_read_bool(np, "aspeed,ext-push-pull"))
                        reg |= WDT_PUSH_PULL_MAGIC;
                else
                        reg |= WDT_OPEN_DRAIN_MAGIC;

                writel(reg, wdt->base + WDT_RESET_WIDTH);

                reg &= config->ext_pulse_width_mask;
                if (of_property_read_bool(np, "aspeed,ext-active-high"))
                        reg |= WDT_ACTIVE_HIGH_MAGIC;
                else
                        reg |= WDT_ACTIVE_LOW_MAGIC;

                writel(reg, wdt->base + WDT_RESET_WIDTH);
        }

        if (!of_property_read_u32(np, "aspeed,ext-pulse-duration", &duration)) {
                u32 max_duration = config->ext_pulse_width_mask + 1;

                if (duration == 0 || duration > max_duration) {
                        dev_err(&pdev->dev, "Invalid pulse duration: %uus\n",
                                        duration);
                        duration = max(1U, min(max_duration, duration));
                        dev_info(&pdev->dev, "Pulse duration set to %uus\n",
                                        duration);
                }

                /*
                 * The watchdog is always configured with a 1MHz source, so
                 * there is no need to scale the microsecond value. However we
                 * need to offset it - from the datasheet:
                 *
                 * "This register decides the asserting duration of wdt_ext and
                 * wdt_rstarm signal. The default value is 0xFF. It means the
                 * default asserting duration of wdt_ext and wdt_rstarm is
                 * 256us."
                 *
                 * This implies a value of 0 gives a 1us pulse.
                 */
                writel(duration - 1, wdt->base + WDT_RESET_WIDTH);
        }

        status = readl(wdt->base + WDT_TIMEOUT_STATUS);
        if (status & WDT_TIMEOUT_STATUS_BOOT_SECONDARY)
                wdt->wdd.bootstatus = WDIOF_CARDRESET;

        ret = devm_watchdog_register_device(&pdev->dev, &wdt->wdd);
        if (ret) {
                dev_err(&pdev->dev, "failed to register\n");
                return ret;
        }

        return 0;
}

static struct platform_driver aspeed_watchdog_driver = {
        .probe = aspeed_wdt_probe,
        .driver = {
                .name = KBUILD_MODNAME,
                .of_match_table = of_match_ptr(aspeed_wdt_of_table),
        },
};

static int __init aspeed_wdt_init(void)
{
        return platform_driver_register(&aspeed_watchdog_driver);
}
arch_initcall(aspeed_wdt_init);

static void __exit aspeed_wdt_exit(void)
{
        platform_driver_unregister(&aspeed_watchdog_driver);
}
module_exit(aspeed_wdt_exit);

MODULE_DESCRIPTION("Aspeed Watchdog Driver");
MODULE_LICENSE("GPL");