// SPDX-License-Identifier: GPL-2.0-only
/* linux/drivers/char/pc8736x_gpio.c

   National Semiconductor PC8736x GPIO driver.  Allows a user space
   process to play with the GPIO pins.

   Copyright (c) 2005,2006 Jim Cromie <jim.cromie@gmail.com>

   adapted from linux/drivers/char/scx200_gpio.c
   Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>,
*/

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/cdev.h>
#include <linux/io.h>
#include <linux/ioport.h>
#include <linux/mutex.h>
#include <linux/nsc_gpio.h>
#include <linux/platform_device.h>
#include <linux/uaccess.h>

#define DEVNAME "pc8736x_gpio"

MODULE_AUTHOR("Jim Cromie <jim.cromie@gmail.com>");
MODULE_DESCRIPTION("NatSemi/Winbond PC-8736x GPIO Pin Driver");
MODULE_LICENSE("GPL");

static int major;               /* default to dynamic major */
module_param(major, int, 0);
MODULE_PARM_DESC(major, "Major device number");

static DEFINE_MUTEX(pc8736x_gpio_config_lock);
static unsigned pc8736x_gpio_base;
static u8 pc8736x_gpio_shadow[4];

#define SIO_BASE1       0x2E    /* 1st command-reg to check */
#define SIO_BASE2       0x4E    /* alt command-reg to check */

#define SIO_SID         0x20    /* SuperI/O ID Register */
#define SIO_SID_PC87365 0xe5    /* Expected value in ID Register for PC87365 */
#define SIO_SID_PC87366 0xe9    /* Expected value in ID Register for PC87366 */

#define SIO_CF1         0x21    /* chip config, bit0 is chip enable */

#define PC8736X_GPIO_RANGE      16 /* ioaddr range */
#define PC8736X_GPIO_CT         32 /* minors matching 4 8 bit ports */

#define SIO_UNIT_SEL    0x7     /* unit select reg */
#define SIO_UNIT_ACT    0x30    /* unit enable */
#define SIO_GPIO_UNIT   0x7     /* unit number of GPIO */
#define SIO_VLM_UNIT    0x0D
#define SIO_TMS_UNIT    0x0E

/* config-space addrs to read/write each unit's runtime addr */
#define SIO_BASE_HADDR          0x60
#define SIO_BASE_LADDR          0x61

/* GPIO config-space pin-control addresses */
#define SIO_GPIO_PIN_SELECT     0xF0
#define SIO_GPIO_PIN_CONFIG     0xF1
#define SIO_GPIO_PIN_EVENT      0xF2

static unsigned char superio_cmd = 0;
static unsigned char selected_device = 0xFF;    /* bogus start val */

/* GPIO port runtime access, functionality */
static int port_offset[] = { 0, 4, 8, 10 };     /* non-uniform offsets ! */
/* static int event_capable[] = { 1, 1, 0, 0 };   ports 2,3 are hobbled */

#define PORT_OUT        0
#define PORT_IN         1
#define PORT_EVT_EN     2
#define PORT_EVT_STST   3

static struct platform_device *pdev;  /* use in dev_*() */

static inline void superio_outb(int addr, int val)
{
        outb_p(addr, superio_cmd);
        outb_p(val, superio_cmd + 1);
}

static inline int superio_inb(int addr)
{
        outb_p(addr, superio_cmd);
        return inb_p(superio_cmd + 1);
}

static int pc8736x_superio_present(void)
{
        int id;

        /* try the 2 possible values, read a hardware reg to verify */
        superio_cmd = SIO_BASE1;
        id = superio_inb(SIO_SID);
        if (id == SIO_SID_PC87365 || id == SIO_SID_PC87366)
                return superio_cmd;

        superio_cmd = SIO_BASE2;
        id = superio_inb(SIO_SID);
        if (id == SIO_SID_PC87365 || id == SIO_SID_PC87366)
                return superio_cmd;

        return 0;
}

static void device_select(unsigned devldn)
{
        superio_outb(SIO_UNIT_SEL, devldn);
        selected_device = devldn;
}

static void select_pin(unsigned iminor)
{
        /* select GPIO port/pin from device minor number */
        device_select(SIO_GPIO_UNIT);
        superio_outb(SIO_GPIO_PIN_SELECT,
                     ((iminor << 1) & 0xF0) | (iminor & 0x7));
}

static inline u32 pc8736x_gpio_configure_fn(unsigned index, u32 mask, u32 bits,
                                            u32 func_slct)
{
        u32 config, new_config;

        mutex_lock(&pc8736x_gpio_config_lock);

        device_select(SIO_GPIO_UNIT);
        select_pin(index);

        /* read current config value */
        config = superio_inb(func_slct);

        /* set new config */
        new_config = (config & mask) | bits;
        superio_outb(func_slct, new_config);

        mutex_unlock(&pc8736x_gpio_config_lock);

        return config;
}

static u32 pc8736x_gpio_configure(unsigned index, u32 mask, u32 bits)
{
        return pc8736x_gpio_configure_fn(index, mask, bits,
                                         SIO_GPIO_PIN_CONFIG);
}

static int pc8736x_gpio_get(unsigned minor)
{
        int port, bit, val;

        port = minor >> 3;
        bit = minor & 7;
        val = inb_p(pc8736x_gpio_base + port_offset[port] + PORT_IN);
        val >>= bit;
        val &= 1;

        dev_dbg(&pdev->dev, "_gpio_get(%d from %x bit %d) == val %d\n",
                minor, pc8736x_gpio_base + port_offset[port] + PORT_IN, bit,
                val);

        return val;
}

static void pc8736x_gpio_set(unsigned minor, int val)
{
        int port, bit, curval;

        minor &= 0x1f;
        port = minor >> 3;
        bit = minor & 7;
        curval = inb_p(pc8736x_gpio_base + port_offset[port] + PORT_OUT);

        dev_dbg(&pdev->dev, "addr:%x cur:%x bit-pos:%d cur-bit:%x + new:%d -> bit-new:%d\n",
                pc8736x_gpio_base + port_offset[port] + PORT_OUT,
                curval, bit, (curval & ~(1 << bit)), val, (val << bit));

        val = (curval & ~(1 << bit)) | (val << bit);

        dev_dbg(&pdev->dev, "gpio_set(minor:%d port:%d bit:%d)"
                " %2x -> %2x\n", minor, port, bit, curval, val);

        outb_p(val, pc8736x_gpio_base + port_offset[port] + PORT_OUT);

        curval = inb_p(pc8736x_gpio_base + port_offset[port] + PORT_OUT);
        val = inb_p(pc8736x_gpio_base + port_offset[port] + PORT_IN);

        dev_dbg(&pdev->dev, "wrote %x, read: %x\n", curval, val);
        pc8736x_gpio_shadow[port] = val;
}

static int pc8736x_gpio_current(unsigned minor)
{
        int port, bit;
        minor &= 0x1f;
        port = minor >> 3;
        bit = minor & 7;
        return ((pc8736x_gpio_shadow[port] >> bit) & 0x01);
}

static void pc8736x_gpio_change(unsigned index)
{
        pc8736x_gpio_set(index, !pc8736x_gpio_current(index));
}

static struct nsc_gpio_ops pc8736x_gpio_ops = {
        .owner          = THIS_MODULE,
        .gpio_config    = pc8736x_gpio_configure,
        .gpio_dump      = nsc_gpio_dump,
        .gpio_get       = pc8736x_gpio_get,
        .gpio_set       = pc8736x_gpio_set,
        .gpio_change    = pc8736x_gpio_change,
        .gpio_current   = pc8736x_gpio_current
};

static int pc8736x_gpio_open(struct inode *inode, struct file *file)
{
        unsigned m = iminor(inode);
        file->private_data = &pc8736x_gpio_ops;

        dev_dbg(&pdev->dev, "open %d\n", m);

        if (m >= PC8736X_GPIO_CT)
                return -EINVAL;
        return nonseekable_open(inode, file);
}

static const struct file_operations pc8736x_gpio_fileops = {
        .owner  = THIS_MODULE,
        .open   = pc8736x_gpio_open,
        .write  = nsc_gpio_write,
        .read   = nsc_gpio_read,
};

static void __init pc8736x_init_shadow(void)
{
        int port;

        /* read the current values driven on the GPIO signals */
        for (port = 0; port < 4; ++port)
                pc8736x_gpio_shadow[port]
                    = inb_p(pc8736x_gpio_base + port_offset[port]
                            + PORT_OUT);

}

static struct cdev pc8736x_gpio_cdev;

static int __init pc8736x_gpio_init(void)
{
        int rc;
        dev_t devid;

        pdev = platform_device_alloc(DEVNAME, 0);
        if (!pdev)
                return -ENOMEM;

        rc = platform_device_add(pdev);
        if (rc) {
                rc = -ENODEV;
                goto undo_platform_dev_alloc;
        }
        dev_info(&pdev->dev, "NatSemi pc8736x GPIO Driver Initializing\n");

        if (!pc8736x_superio_present()) {
                rc = -ENODEV;
                dev_err(&pdev->dev, "no device found\n");
                goto undo_platform_dev_add;
        }
        pc8736x_gpio_ops.dev = &pdev->dev;

        /* Verify that chip and it's GPIO unit are both enabled.
           My BIOS does this, so I take minimum action here
         */
        rc = superio_inb(SIO_CF1);
        if (!(rc & 0x01)) {
                rc = -ENODEV;
                dev_err(&pdev->dev, "device not enabled\n");
                goto undo_platform_dev_add;
        }
        device_select(SIO_GPIO_UNIT);
        if (!superio_inb(SIO_UNIT_ACT)) {
                rc = -ENODEV;
                dev_err(&pdev->dev, "GPIO unit not enabled\n");
                goto undo_platform_dev_add;
        }

        /* read the GPIO unit base addr that chip responds to */
        pc8736x_gpio_base = (superio_inb(SIO_BASE_HADDR) << 8
                             | superio_inb(SIO_BASE_LADDR));

        if (!request_region(pc8736x_gpio_base, PC8736X_GPIO_RANGE, DEVNAME)) {
                rc = -ENODEV;
                dev_err(&pdev->dev, "GPIO ioport %x busy\n",
                        pc8736x_gpio_base);
                goto undo_platform_dev_add;
        }
        dev_info(&pdev->dev, "GPIO ioport %x reserved\n", pc8736x_gpio_base);

        if (major) {
                devid = MKDEV(major, 0);
                rc = register_chrdev_region(devid, PC8736X_GPIO_CT, DEVNAME);
        } else {
                rc = alloc_chrdev_region(&devid, 0, PC8736X_GPIO_CT, DEVNAME);
                major = MAJOR(devid);
        }

        if (rc < 0) {
                dev_err(&pdev->dev, "register-chrdev failed: %d\n", rc);
                goto undo_request_region;
        }
        if (!major) {
                major = rc;
                dev_dbg(&pdev->dev, "got dynamic major %d\n", major);
        }

        pc8736x_init_shadow();

        /* ignore minor errs, and succeed */
        cdev_init(&pc8736x_gpio_cdev, &pc8736x_gpio_fileops);
        cdev_add(&pc8736x_gpio_cdev, devid, PC8736X_GPIO_CT);

        return 0;

undo_request_region:
        release_region(pc8736x_gpio_base, PC8736X_GPIO_RANGE);
undo_platform_dev_add:
        platform_device_del(pdev);
undo_platform_dev_alloc:
        platform_device_put(pdev);

        return rc;
}

static void __exit pc8736x_gpio_cleanup(void)
{
        dev_dbg(&pdev->dev, "cleanup\n");

        cdev_del(&pc8736x_gpio_cdev);
        unregister_chrdev_region(MKDEV(major,0), PC8736X_GPIO_CT);
        release_region(pc8736x_gpio_base, PC8736X_GPIO_RANGE);

        platform_device_unregister(pdev);
}

module_init(pc8736x_gpio_init);
module_exit(pc8736x_gpio_cleanup);