// SPDX-License-Identifier: GPL-2.0-or-later
/***************************************************************************
 *   Copyright (C) 2010-2012 Hans de Goede <hdegoede@redhat.com>           *
 *                                                                         *
 ***************************************************************************/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/init.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/acpi.h>
#include <linux/delay.h>
#include <linux/fs.h>
#include <linux/watchdog.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include "sch56xx-common.h"

/* Insmod parameters */
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
        __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

#define SIO_SCH56XX_LD_EM       0x0C    /* Embedded uController Logical Dev */
#define SIO_UNLOCK_KEY          0x55    /* Key to enable Super-I/O */
#define SIO_LOCK_KEY            0xAA    /* Key to disable Super-I/O */

#define SIO_REG_LDSEL           0x07    /* Logical device select */
#define SIO_REG_DEVID           0x20    /* Device ID */
#define SIO_REG_ENABLE          0x30    /* Logical device enable */
#define SIO_REG_ADDR            0x66    /* Logical device address (2 bytes) */

#define SIO_SCH5627_ID          0xC6    /* Chipset ID */
#define SIO_SCH5636_ID          0xC7    /* Chipset ID */

#define REGION_LENGTH           10

#define SCH56XX_CMD_READ        0x02
#define SCH56XX_CMD_WRITE       0x03

/* Watchdog registers */
#define SCH56XX_REG_WDOG_PRESET         0x58B
#define SCH56XX_REG_WDOG_CONTROL        0x58C
#define SCH56XX_WDOG_TIME_BASE_SEC      0x01
#define SCH56XX_REG_WDOG_OUTPUT_ENABLE  0x58E
#define SCH56XX_WDOG_OUTPUT_ENABLE      0x02

struct sch56xx_watchdog_data {
        u16 addr;
        struct mutex *io_lock;
        struct watchdog_info wdinfo;
        struct watchdog_device wddev;
        u8 watchdog_preset;
        u8 watchdog_control;
        u8 watchdog_output_enable;
};

static struct platform_device *sch56xx_pdev;

/* Super I/O functions */
static inline int superio_inb(int base, int reg)
{
        outb(reg, base);
        return inb(base + 1);
}

static inline int superio_enter(int base)
{
        /* Don't step on other drivers' I/O space by accident */
        if (!request_muxed_region(base, 2, "sch56xx")) {
                pr_err("I/O address 0x%04x already in use\n", base);
                return -EBUSY;
        }

        outb(SIO_UNLOCK_KEY, base);

        return 0;
}

static inline void superio_select(int base, int ld)
{
        outb(SIO_REG_LDSEL, base);
        outb(ld, base + 1);
}

static inline void superio_exit(int base)
{
        outb(SIO_LOCK_KEY, base);
        release_region(base, 2);
}

static int sch56xx_send_cmd(u16 addr, u8 cmd, u16 reg, u8 v)
{
        u8 val;
        int i;
        /*
         * According to SMSC for the commands we use the maximum time for
         * the EM to respond is 15 ms, but testing shows in practice it
         * responds within 15-32 reads, so we first busy poll, and if
         * that fails sleep a bit and try again until we are way past
         * the 15 ms maximum response time.
         */
        const int max_busy_polls = 64;
        const int max_lazy_polls = 32;

        /* (Optional) Write-Clear the EC to Host Mailbox Register */
        val = inb(addr + 1);
        outb(val, addr + 1);

        /* Set Mailbox Address Pointer to first location in Region 1 */
        outb(0x00, addr + 2);
        outb(0x80, addr + 3);

        /* Write Request Packet Header */
        outb(cmd, addr + 4); /* VREG Access Type read:0x02 write:0x03 */
        outb(0x01, addr + 5); /* # of Entries: 1 Byte (8-bit) */
        outb(0x04, addr + 2); /* Mailbox AP to first data entry loc. */

        /* Write Value field */
        if (cmd == SCH56XX_CMD_WRITE)
                outb(v, addr + 4);

        /* Write Address field */
        outb(reg & 0xff, addr + 6);
        outb(reg >> 8, addr + 7);

        /* Execute the Random Access Command */
        outb(0x01, addr); /* Write 01h to the Host-to-EC register */

        /* EM Interface Polling "Algorithm" */
        for (i = 0; i < max_busy_polls + max_lazy_polls; i++) {
                if (i >= max_busy_polls)
                        msleep(1);
                /* Read Interrupt source Register */
                val = inb(addr + 8);
                /* Write Clear the interrupt source bits */
                if (val)
                        outb(val, addr + 8);
                /* Command Completed ? */
                if (val & 0x01)
                        break;
        }
        if (i == max_busy_polls + max_lazy_polls) {
                pr_err("Max retries exceeded reading virtual register 0x%04hx (%d)\n",
                       reg, 1);
                return -EIO;
        }

        /*
         * According to SMSC we may need to retry this, but sofar I've always
         * seen this succeed in 1 try.
         */
        for (i = 0; i < max_busy_polls; i++) {
                /* Read EC-to-Host Register */
                val = inb(addr + 1);
                /* Command Completed ? */
                if (val == 0x01)
                        break;

                if (i == 0)
                        pr_warn("EC reports: 0x%02x reading virtual register 0x%04hx\n",
                                (unsigned int)val, reg);
        }
        if (i == max_busy_polls) {
                pr_err("Max retries exceeded reading virtual register 0x%04hx (%d)\n",
                       reg, 2);
                return -EIO;
        }

        /*
         * According to the SMSC app note we should now do:
         *
         * Set Mailbox Address Pointer to first location in Region 1 *
         * outb(0x00, addr + 2);
         * outb(0x80, addr + 3);
         *
         * But if we do that things don't work, so let's not.
         */

        /* Read Value field */
        if (cmd == SCH56XX_CMD_READ)
                return inb(addr + 4);

        return 0;
}

int sch56xx_read_virtual_reg(u16 addr, u16 reg)
{
        return sch56xx_send_cmd(addr, SCH56XX_CMD_READ, reg, 0);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg);

int sch56xx_write_virtual_reg(u16 addr, u16 reg, u8 val)
{
        return sch56xx_send_cmd(addr, SCH56XX_CMD_WRITE, reg, val);
}
EXPORT_SYMBOL(sch56xx_write_virtual_reg);

int sch56xx_read_virtual_reg16(u16 addr, u16 reg)
{
        int lsb, msb;

        /* Read LSB first, this will cause the matching MSB to be latched */
        lsb = sch56xx_read_virtual_reg(addr, reg);
        if (lsb < 0)
                return lsb;

        msb = sch56xx_read_virtual_reg(addr, reg + 1);
        if (msb < 0)
                return msb;

        return lsb | (msb << 8);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg16);

int sch56xx_read_virtual_reg12(u16 addr, u16 msb_reg, u16 lsn_reg,
                               int high_nibble)
{
        int msb, lsn;

        /* Read MSB first, this will cause the matching LSN to be latched */
        msb = sch56xx_read_virtual_reg(addr, msb_reg);
        if (msb < 0)
                return msb;

        lsn = sch56xx_read_virtual_reg(addr, lsn_reg);
        if (lsn < 0)
                return lsn;

        if (high_nibble)
                return (msb << 4) | (lsn >> 4);
        else
                return (msb << 4) | (lsn & 0x0f);
}
EXPORT_SYMBOL(sch56xx_read_virtual_reg12);

/*
 * Watchdog routines
 */

static int watchdog_set_timeout(struct watchdog_device *wddev,
                                unsigned int timeout)
{
        struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
        unsigned int resolution;
        u8 control;
        int ret;

        /* 1 second or 60 second resolution? */
        if (timeout <= 255)
                resolution = 1;
        else
                resolution = 60;

        if (timeout < resolution || timeout > (resolution * 255))
                return -EINVAL;

        if (resolution == 1)
                control = data->watchdog_control | SCH56XX_WDOG_TIME_BASE_SEC;
        else
                control = data->watchdog_control & ~SCH56XX_WDOG_TIME_BASE_SEC;

        if (data->watchdog_control != control) {
                mutex_lock(data->io_lock);
                ret = sch56xx_write_virtual_reg(data->addr,
                                                SCH56XX_REG_WDOG_CONTROL,
                                                control);
                mutex_unlock(data->io_lock);
                if (ret)
                        return ret;

                data->watchdog_control = control;
        }

        /*
         * Remember new timeout value, but do not write as that (re)starts
         * the watchdog countdown.
         */
        data->watchdog_preset = DIV_ROUND_UP(timeout, resolution);
        wddev->timeout = data->watchdog_preset * resolution;

        return 0;
}

static int watchdog_start(struct watchdog_device *wddev)
{
        struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
        int ret;
        u8 val;

        /*
         * The sch56xx's watchdog cannot really be started / stopped
         * it is always running, but we can avoid the timer expiring
         * from causing a system reset by clearing the output enable bit.
         *
         * The sch56xx's watchdog will set the watchdog event bit, bit 0
         * of the second interrupt source register (at base-address + 9),
         * when the timer expires.
         *
         * This will only cause a system reset if the 0-1 flank happens when
         * output enable is true. Setting output enable after the flank will
         * not cause a reset, nor will the timer expiring a second time.
         * This means we must clear the watchdog event bit in case it is set.
         *
         * The timer may still be running (after a recent watchdog_stop) and
         * mere milliseconds away from expiring, so the timer must be reset
         * first!
         */

        mutex_lock(data->io_lock);

        /* 1. Reset the watchdog countdown counter */
        ret = sch56xx_write_virtual_reg(data->addr, SCH56XX_REG_WDOG_PRESET,
                                        data->watchdog_preset);
        if (ret)
                goto leave;

        /* 2. Enable output */
        val = data->watchdog_output_enable | SCH56XX_WDOG_OUTPUT_ENABLE;
        ret = sch56xx_write_virtual_reg(data->addr,
                                        SCH56XX_REG_WDOG_OUTPUT_ENABLE, val);
        if (ret)
                goto leave;

        data->watchdog_output_enable = val;

        /* 3. Clear the watchdog event bit if set */
        val = inb(data->addr + 9);
        if (val & 0x01)
                outb(0x01, data->addr + 9);

leave:
        mutex_unlock(data->io_lock);
        return ret;
}

static int watchdog_trigger(struct watchdog_device *wddev)
{
        struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
        int ret;

        /* Reset the watchdog countdown counter */
        mutex_lock(data->io_lock);
        ret = sch56xx_write_virtual_reg(data->addr, SCH56XX_REG_WDOG_PRESET,
                                        data->watchdog_preset);
        mutex_unlock(data->io_lock);

        return ret;
}

static int watchdog_stop(struct watchdog_device *wddev)
{
        struct sch56xx_watchdog_data *data = watchdog_get_drvdata(wddev);
        int ret = 0;
        u8 val;

        val = data->watchdog_output_enable & ~SCH56XX_WDOG_OUTPUT_ENABLE;
        mutex_lock(data->io_lock);
        ret = sch56xx_write_virtual_reg(data->addr,
                                        SCH56XX_REG_WDOG_OUTPUT_ENABLE, val);
        mutex_unlock(data->io_lock);
        if (ret)
                return ret;

        data->watchdog_output_enable = val;
        return 0;
}

static const struct watchdog_ops watchdog_ops = {
        .owner          = THIS_MODULE,
        .start          = watchdog_start,
        .stop           = watchdog_stop,
        .ping           = watchdog_trigger,
        .set_timeout    = watchdog_set_timeout,
};

void sch56xx_watchdog_register(struct device *parent, u16 addr, u32 revision,
                               struct mutex *io_lock, int check_enabled)
{
        struct sch56xx_watchdog_data *data;
        int err, control, output_enable;

        /* Cache the watchdog registers */
        mutex_lock(io_lock);
        control =
                sch56xx_read_virtual_reg(addr, SCH56XX_REG_WDOG_CONTROL);
        output_enable =
                sch56xx_read_virtual_reg(addr, SCH56XX_REG_WDOG_OUTPUT_ENABLE);
        mutex_unlock(io_lock);

        if (control < 0)
                return;
        if (output_enable < 0)
                return;
        if (check_enabled && !(output_enable & SCH56XX_WDOG_OUTPUT_ENABLE)) {
                pr_warn("Watchdog not enabled by BIOS, not registering\n");
                return;
        }

        data = devm_kzalloc(parent, sizeof(struct sch56xx_watchdog_data), GFP_KERNEL);
        if (!data)
                return;

        data->addr = addr;
        data->io_lock = io_lock;

        strscpy(data->wdinfo.identity, "sch56xx watchdog", sizeof(data->wdinfo.identity));
        data->wdinfo.firmware_version = revision;
        data->wdinfo.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT;
        if (!nowayout)
                data->wdinfo.options |= WDIOF_MAGICCLOSE;

        data->wddev.info = &data->wdinfo;
        data->wddev.ops = &watchdog_ops;
        data->wddev.parent = parent;
        data->wddev.timeout = 60;
        data->wddev.min_timeout = 1;
        data->wddev.max_timeout = 255 * 60;
        watchdog_set_nowayout(&data->wddev, nowayout);
        if (output_enable & SCH56XX_WDOG_OUTPUT_ENABLE)
                set_bit(WDOG_ACTIVE, &data->wddev.status);

        /* Since the watchdog uses a downcounter there is no register to read
           the BIOS set timeout from (if any was set at all) ->
           Choose a preset which will give us a 1 minute timeout */
        if (control & SCH56XX_WDOG_TIME_BASE_SEC)
                data->watchdog_preset = 60; /* seconds */
        else
                data->watchdog_preset = 1; /* minute */

        data->watchdog_control = control;
        data->watchdog_output_enable = output_enable;

        watchdog_set_drvdata(&data->wddev, data);
        err = devm_watchdog_register_device(parent, &data->wddev);
        if (err) {
                pr_err("Registering watchdog chardev: %d\n", err);
                devm_kfree(parent, data);
        }
}
EXPORT_SYMBOL(sch56xx_watchdog_register);

/*
 * platform dev find, add and remove functions
 */

static int __init sch56xx_find(int sioaddr, const char **name)
{
        u8 devid;
        unsigned short address;
        int err;

        err = superio_enter(sioaddr);
        if (err)
                return err;

        devid = superio_inb(sioaddr, SIO_REG_DEVID);
        switch (devid) {
        case SIO_SCH5627_ID:
                *name = "sch5627";
                break;
        case SIO_SCH5636_ID:
                *name = "sch5636";
                break;
        default:
                pr_debug("Unsupported device id: 0x%02x\n",
                         (unsigned int)devid);
                err = -ENODEV;
                goto exit;
        }

        superio_select(sioaddr, SIO_SCH56XX_LD_EM);

        if (!(superio_inb(sioaddr, SIO_REG_ENABLE) & 0x01)) {
                pr_warn("Device not activated\n");
                err = -ENODEV;
                goto exit;
        }

        /*
         * Warning the order of the low / high byte is the other way around
         * as on most other superio devices!!
         */
        address = superio_inb(sioaddr, SIO_REG_ADDR) |
                   superio_inb(sioaddr, SIO_REG_ADDR + 1) << 8;
        if (address == 0) {
                pr_warn("Base address not set\n");
                err = -ENODEV;
                goto exit;
        }
        err = address;

exit:
        superio_exit(sioaddr);
        return err;
}

static int __init sch56xx_device_add(int address, const char *name)
{
        struct resource res = {
                .start  = address,
                .end    = address + REGION_LENGTH - 1,
                .name   = name,
                .flags  = IORESOURCE_IO,
        };
        int err;

        err = acpi_check_resource_conflict(&res);
        if (err)
                return err;

        sch56xx_pdev = platform_device_register_simple(name, -1, &res, 1);

        return PTR_ERR_OR_ZERO(sch56xx_pdev);
}

static int __init sch56xx_init(void)
{
        int address;
        const char *name = NULL;

        address = sch56xx_find(0x4e, &name);
        if (address < 0)
                address = sch56xx_find(0x2e, &name);
        if (address < 0)
                return address;

        return sch56xx_device_add(address, name);
}

static void __exit sch56xx_exit(void)
{
        platform_device_unregister(sch56xx_pdev);
}

MODULE_DESCRIPTION("SMSC SCH56xx Hardware Monitoring Common Code");
MODULE_AUTHOR("Hans de Goede <hdegoede@redhat.com>");
MODULE_LICENSE("GPL");

module_init(sch56xx_init);
module_exit(sch56xx_exit);