// SPDX-License-Identifier: GPL-2.0-or-later
/*
    Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>

    National Semiconductor SCx200 ACCESS.bus support
    Also supports the AMD CS5535 and AMD CS5536

    Based on i2c-keywest.c which is:
        Copyright (c) 2001 Benjamin Herrenschmidt <benh@kernel.crashing.org>
        Copyright (c) 2000 Philip Edelbrock <phil@stimpy.netroedge.com>

*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/i2c.h>
#include <linux/pci.h>
#include <linux/platform_device.h>
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/io.h>

#include <linux/scx200.h>

MODULE_AUTHOR("Christer Weinigel <wingel@nano-system.com>");
MODULE_DESCRIPTION("NatSemi SCx200 ACCESS.bus Driver");
MODULE_ALIAS("platform:cs5535-smb");
MODULE_LICENSE("GPL");

#define MAX_DEVICES 4
static int base[MAX_DEVICES] = { 0x820, 0x840 };
module_param_hw_array(base, int, ioport, NULL, 0);
MODULE_PARM_DESC(base, "Base addresses for the ACCESS.bus controllers");

#define POLL_TIMEOUT    (HZ/5)

enum scx200_acb_state {
        state_idle,
        state_address,
        state_command,
        state_repeat_start,
        state_quick,
        state_read,
        state_write,
};

static const char *scx200_acb_state_name[] = {
        "idle",
        "address",
        "command",
        "repeat_start",
        "quick",
        "read",
        "write",
};

/* Physical interface */
struct scx200_acb_iface {
        struct scx200_acb_iface *next;
        struct i2c_adapter adapter;
        unsigned base;
        struct mutex mutex;

        /* State machine data */
        enum scx200_acb_state state;
        int result;
        u8 address_byte;
        u8 command;
        u8 *ptr;
        char needs_reset;
        unsigned len;
};

/* Register Definitions */
#define ACBSDA          (iface->base + 0)
#define ACBST           (iface->base + 1)
#define    ACBST_SDAST          0x40 /* SDA Status */
#define    ACBST_BER            0x20
#define    ACBST_NEGACK         0x10 /* Negative Acknowledge */
#define    ACBST_STASTR         0x08 /* Stall After Start */
#define    ACBST_MASTER         0x02
#define ACBCST          (iface->base + 2)
#define    ACBCST_BB            0x02
#define ACBCTL1         (iface->base + 3)
#define    ACBCTL1_STASTRE      0x80
#define    ACBCTL1_NMINTE       0x40
#define    ACBCTL1_ACK          0x10
#define    ACBCTL1_STOP         0x02
#define    ACBCTL1_START        0x01
#define ACBADDR         (iface->base + 4)
#define ACBCTL2         (iface->base + 5)
#define    ACBCTL2_ENABLE       0x01

/************************************************************************/

static void scx200_acb_machine(struct scx200_acb_iface *iface, u8 status)
{
        const char *errmsg;

        dev_dbg(&iface->adapter.dev, "state %s, status = 0x%02x\n",
                scx200_acb_state_name[iface->state], status);

        if (status & ACBST_BER) {
                errmsg = "bus error";
                goto error;
        }
        if (!(status & ACBST_MASTER)) {
                errmsg = "not master";
                goto error;
        }
        if (status & ACBST_NEGACK) {
                dev_dbg(&iface->adapter.dev, "negative ack in state %s\n",
                        scx200_acb_state_name[iface->state]);

                iface->state = state_idle;
                iface->result = -ENXIO;

                outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
                outb(ACBST_STASTR | ACBST_NEGACK, ACBST);

                /* Reset the status register */
                outb(0, ACBST);
                return;
        }

        switch (iface->state) {
        case state_idle:
                dev_warn(&iface->adapter.dev, "interrupt in idle state\n");
                break;

        case state_address:
                /* Do a pointer write first */
                outb(iface->address_byte & ~1, ACBSDA);

                iface->state = state_command;
                break;

        case state_command:
                outb(iface->command, ACBSDA);

                if (iface->address_byte & 1)
                        iface->state = state_repeat_start;
                else
                        iface->state = state_write;
                break;

        case state_repeat_start:
                outb(inb(ACBCTL1) | ACBCTL1_START, ACBCTL1);
                fallthrough;

        case state_quick:
                if (iface->address_byte & 1) {
                        if (iface->len == 1)
                                outb(inb(ACBCTL1) | ACBCTL1_ACK, ACBCTL1);
                        else
                                outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);
                        outb(iface->address_byte, ACBSDA);

                        iface->state = state_read;
                } else {
                        outb(iface->address_byte, ACBSDA);

                        iface->state = state_write;
                }
                break;

        case state_read:
                /* Set ACK if _next_ byte will be the last one */
                if (iface->len == 2)
                        outb(inb(ACBCTL1) | ACBCTL1_ACK, ACBCTL1);
                else
                        outb(inb(ACBCTL1) & ~ACBCTL1_ACK, ACBCTL1);

                if (iface->len == 1) {
                        iface->result = 0;
                        iface->state = state_idle;
                        outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
                }

                *iface->ptr++ = inb(ACBSDA);
                --iface->len;

                break;

        case state_write:
                if (iface->len == 0) {
                        iface->result = 0;
                        iface->state = state_idle;
                        outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
                        break;
                }

                outb(*iface->ptr++, ACBSDA);
                --iface->len;

                break;
        }

        return;

 error:
        dev_err(&iface->adapter.dev,
                "%s in state %s (addr=0x%02x, len=%d, status=0x%02x)\n", errmsg,
                scx200_acb_state_name[iface->state], iface->address_byte,
                iface->len, status);

        iface->state = state_idle;
        iface->result = -EIO;
        iface->needs_reset = 1;
}

static void scx200_acb_poll(struct scx200_acb_iface *iface)
{
        u8 status;
        unsigned long timeout;

        timeout = jiffies + POLL_TIMEOUT;
        while (1) {
                status = inb(ACBST);

                /* Reset the status register to avoid the hang */
                outb(0, ACBST);

                if ((status & (ACBST_SDAST|ACBST_BER|ACBST_NEGACK)) != 0) {
                        scx200_acb_machine(iface, status);
                        return;
                }
                if (time_after(jiffies, timeout))
                        break;
                cpu_relax();
                cond_resched();
        }

        dev_err(&iface->adapter.dev, "timeout in state %s\n",
                scx200_acb_state_name[iface->state]);

        iface->state = state_idle;
        iface->result = -EIO;
        iface->needs_reset = 1;
}

static void scx200_acb_reset(struct scx200_acb_iface *iface)
{
        /* Disable the ACCESS.bus device and Configure the SCL
           frequency: 16 clock cycles */
        outb(0x70, ACBCTL2);
        /* Polling mode */
        outb(0, ACBCTL1);
        /* Disable slave address */
        outb(0, ACBADDR);
        /* Enable the ACCESS.bus device */
        outb(inb(ACBCTL2) | ACBCTL2_ENABLE, ACBCTL2);
        /* Free STALL after START */
        outb(inb(ACBCTL1) & ~(ACBCTL1_STASTRE | ACBCTL1_NMINTE), ACBCTL1);
        /* Send a STOP */
        outb(inb(ACBCTL1) | ACBCTL1_STOP, ACBCTL1);
        /* Clear BER, NEGACK and STASTR bits */
        outb(ACBST_BER | ACBST_NEGACK | ACBST_STASTR, ACBST);
        /* Clear BB bit */
        outb(inb(ACBCST) | ACBCST_BB, ACBCST);
}

static s32 scx200_acb_smbus_xfer(struct i2c_adapter *adapter,
                                 u16 address, unsigned short flags,
                                 char rw, u8 command, int size,
                                 union i2c_smbus_data *data)
{
        struct scx200_acb_iface *iface = i2c_get_adapdata(adapter);
        int len;
        u8 *buffer;
        u16 cur_word;
        int rc;

        switch (size) {
        case I2C_SMBUS_QUICK:
                len = 0;
                buffer = NULL;
                break;

        case I2C_SMBUS_BYTE:
                len = 1;
                buffer = rw ? &data->byte : &command;
                break;

        case I2C_SMBUS_BYTE_DATA:
                len = 1;
                buffer = &data->byte;
                break;

        case I2C_SMBUS_WORD_DATA:
                len = 2;
                cur_word = cpu_to_le16(data->word);
                buffer = (u8 *)&cur_word;
                break;

        case I2C_SMBUS_I2C_BLOCK_DATA:
                len = data->block[0];
                if (len == 0 || len > I2C_SMBUS_BLOCK_MAX)
                        return -EINVAL;
                buffer = &data->block[1];
                break;

        default:
                return -EINVAL;
        }

        dev_dbg(&adapter->dev,
                "size=%d, address=0x%x, command=0x%x, len=%d, read=%d\n",
                size, address, command, len, rw);

        if (!len && rw == I2C_SMBUS_READ) {
                dev_dbg(&adapter->dev, "zero length read\n");
                return -EINVAL;
        }

        mutex_lock(&iface->mutex);

        iface->address_byte = (address << 1) | rw;
        iface->command = command;
        iface->ptr = buffer;
        iface->len = len;
        iface->result = -EINVAL;
        iface->needs_reset = 0;

        outb(inb(ACBCTL1) | ACBCTL1_START, ACBCTL1);

        if (size == I2C_SMBUS_QUICK || size == I2C_SMBUS_BYTE)
                iface->state = state_quick;
        else
                iface->state = state_address;

        while (iface->state != state_idle)
                scx200_acb_poll(iface);

        if (iface->needs_reset)
                scx200_acb_reset(iface);

        rc = iface->result;

        mutex_unlock(&iface->mutex);

        if (rc == 0 && size == I2C_SMBUS_WORD_DATA && rw == I2C_SMBUS_READ)
                data->word = le16_to_cpu(cur_word);

#ifdef DEBUG
        dev_dbg(&adapter->dev, "transfer done, result: %d", rc);
        if (buffer) {
                int i;
                printk(" data:");
                for (i = 0; i < len; ++i)
                        printk(" %02x", buffer[i]);
        }
        printk("\n");
#endif

        return rc;
}

static u32 scx200_acb_func(struct i2c_adapter *adapter)
{
        return I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE |
               I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA |
               I2C_FUNC_SMBUS_I2C_BLOCK;
}

/* For now, we only handle combined mode (smbus) */
static const struct i2c_algorithm scx200_acb_algorithm = {
        .smbus_xfer     = scx200_acb_smbus_xfer,
        .functionality  = scx200_acb_func,
};

static struct scx200_acb_iface *scx200_acb_list;
static DEFINE_MUTEX(scx200_acb_list_mutex);

static int scx200_acb_probe(struct scx200_acb_iface *iface)
{
        u8 val;

        /* Disable the ACCESS.bus device and Configure the SCL
           frequency: 16 clock cycles */
        outb(0x70, ACBCTL2);

        if (inb(ACBCTL2) != 0x70) {
                pr_debug("ACBCTL2 readback failed\n");
                return -ENXIO;
        }

        outb(inb(ACBCTL1) | ACBCTL1_NMINTE, ACBCTL1);

        val = inb(ACBCTL1);
        if (val) {
                pr_debug("disabled, but ACBCTL1=0x%02x\n", val);
                return -ENXIO;
        }

        outb(inb(ACBCTL2) | ACBCTL2_ENABLE, ACBCTL2);

        outb(inb(ACBCTL1) | ACBCTL1_NMINTE, ACBCTL1);

        val = inb(ACBCTL1);
        if ((val & ACBCTL1_NMINTE) != ACBCTL1_NMINTE) {
                pr_debug("enabled, but NMINTE won't be set, ACBCTL1=0x%02x\n",
                         val);
                return -ENXIO;
        }

        return 0;
}

static struct scx200_acb_iface *scx200_create_iface(const char *text,
                struct device *dev, int index)
{
        struct scx200_acb_iface *iface;
        struct i2c_adapter *adapter;

        iface = kzalloc_obj(*iface);
        if (!iface)
                return NULL;

        adapter = &iface->adapter;
        i2c_set_adapdata(adapter, iface);
        snprintf(adapter->name, sizeof(adapter->name), "%s ACB%d", text, index);
        adapter->owner = THIS_MODULE;
        adapter->algo = &scx200_acb_algorithm;
        adapter->class = I2C_CLASS_HWMON;
        adapter->dev.parent = dev;

        mutex_init(&iface->mutex);

        return iface;
}

static int scx200_acb_create(struct scx200_acb_iface *iface)
{
        struct i2c_adapter *adapter;
        int rc;

        adapter = &iface->adapter;

        rc = scx200_acb_probe(iface);
        if (rc) {
                pr_warn("probe failed\n");
                return rc;
        }

        scx200_acb_reset(iface);

        if (i2c_add_adapter(adapter) < 0) {
                pr_err("failed to register\n");
                return -ENODEV;
        }

        if (!adapter->dev.parent) {
                /* If there's no dev, we're tracking (ISA) ifaces manually */
                mutex_lock(&scx200_acb_list_mutex);
                iface->next = scx200_acb_list;
                scx200_acb_list = iface;
                mutex_unlock(&scx200_acb_list_mutex);
        }

        return 0;
}

static struct scx200_acb_iface *scx200_create_dev(const char *text,
                unsigned long base, int index, struct device *dev)
{
        struct scx200_acb_iface *iface;
        int rc;

        iface = scx200_create_iface(text, dev, index);

        if (iface == NULL)
                return NULL;

        if (!request_region(base, 8, iface->adapter.name)) {
                pr_err("can't allocate io 0x%lx-0x%lx\n", base, base + 8 - 1);
                goto errout_free;
        }

        iface->base = base;
        rc = scx200_acb_create(iface);

        if (rc == 0)
                return iface;

        release_region(base, 8);
 errout_free:
        kfree(iface);
        return NULL;
}

static int scx200_probe(struct platform_device *pdev)
{
        struct scx200_acb_iface *iface;
        struct resource *res;

        res = platform_get_resource(pdev, IORESOURCE_IO, 0);
        if (!res)
                return dev_err_probe(&pdev->dev, -ENODEV, "can't fetch device resource info\n");

        iface = scx200_create_dev("CS5535", res->start, 0, &pdev->dev);
        if (!iface)
                return -EIO;

        dev_info(&pdev->dev, "SCx200 device '%s' registered\n",
                        iface->adapter.name);
        platform_set_drvdata(pdev, iface);

        return 0;
}

static void scx200_cleanup_iface(struct scx200_acb_iface *iface)
{
        i2c_del_adapter(&iface->adapter);
        release_region(iface->base, 8);
        kfree(iface);
}

static void scx200_remove(struct platform_device *pdev)
{
        struct scx200_acb_iface *iface;

        iface = platform_get_drvdata(pdev);
        scx200_cleanup_iface(iface);
}

static struct platform_driver scx200_pci_driver = {
        .driver = {
                .name = "cs5535-smb",
        },
        .probe = scx200_probe,
        .remove = scx200_remove,
};

static const struct pci_device_id scx200_isa[] = {
        { PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SCx200_BRIDGE) },
        { PCI_DEVICE(PCI_VENDOR_ID_NS, PCI_DEVICE_ID_NS_SC1100_BRIDGE) },
        { 0, }
};

static __init void scx200_scan_isa(void)
{
        int i;

        if (!pci_dev_present(scx200_isa))
                return;

        for (i = 0; i < MAX_DEVICES; ++i) {
                if (base[i] == 0)
                        continue;

                /* XXX: should we care about failures? */
                scx200_create_dev("SCx200", base[i], i, NULL);
        }
}

static int __init scx200_acb_init(void)
{
        pr_debug("NatSemi SCx200 ACCESS.bus Driver\n");

        /* First scan for ISA-based devices */
        scx200_scan_isa();      /* XXX: should we care about errors? */

        /* If at least one bus was created, init must succeed */
        if (scx200_acb_list)
                return 0;

        /* No ISA devices; register the platform driver for PCI-based devices */
        return platform_driver_register(&scx200_pci_driver);
}

static void __exit scx200_acb_cleanup(void)
{
        struct scx200_acb_iface *iface;

        platform_driver_unregister(&scx200_pci_driver);

        mutex_lock(&scx200_acb_list_mutex);
        while ((iface = scx200_acb_list) != NULL) {
                scx200_acb_list = iface->next;
                mutex_unlock(&scx200_acb_list_mutex);

                scx200_cleanup_iface(iface);

                mutex_lock(&scx200_acb_list_mutex);
        }
        mutex_unlock(&scx200_acb_list_mutex);
}

module_init(scx200_acb_init);
module_exit(scx200_acb_cleanup);