// SPDX-License-Identifier: GPL-2.0-or-later
/*
    Copyright (c) 2002,2003 Alexander Malysh <amalysh@web.de>

*/

/*
   Status: beta

   Supports:
        SIS 630
        SIS 730
        SIS 964

   Notable differences between chips:
        +------------------------+--------------------+-------------------+
        |                        |     SIS630/730     |      SIS964       |
        +------------------------+--------------------+-------------------+
        | Clock                  | 14kHz/56kHz        | 55.56kHz/27.78kHz |
        | SMBus registers offset | 0x80               | 0xE0              |
        | SMB_CNT                | Bit 1 = Slave Busy | Bit 1 = Bus probe |
        |         (not used yet) | Bit 3 is reserved  | Bit 3 = Last byte |
        | SMB_PCOUNT             | Offset + 0x06      | Offset + 0x14     |
        | SMB_COUNT              | 4:0 bits           | 5:0 bits          |
        +------------------------+--------------------+-------------------+
        (Other differences don't affect the functions provided by the driver)

   Note: we assume there can only be one device, with one SMBus interface.
*/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/pci.h>
#include <linux/ioport.h>
#include <linux/i2c.h>
#include <linux/acpi.h>
#include <linux/io.h>

/* SIS964 id is defined here as we are the only file using it */
#define PCI_DEVICE_ID_SI_964    0x0964

/* SIS630/730/964 SMBus registers */
#define SMB_STS                 0x00    /* status */
#define SMB_CNT                 0x02    /* control */
#define SMBHOST_CNT             0x03    /* host control */
#define SMB_ADDR                0x04    /* address */
#define SMB_CMD                 0x05    /* command */
#define SMB_COUNT               0x07    /* byte count */
#define SMB_BYTE                0x08    /* ~0x8F data byte field */

/* SMB_STS register */
#define BYTE_DONE_STS           0x10    /* Byte Done Status / Block Array */
#define SMBCOL_STS              0x04    /* Collision */
#define SMBERR_STS              0x02    /* Device error */

/* SMB_CNT register */
#define MSTO_EN                 0x40    /* Host Master Timeout Enable */
#define SMBCLK_SEL              0x20    /* Host master clock selection */
#define SMB_PROBE               0x02    /* Bus Probe/Slave busy */
#define SMB_HOSTBUSY            0x01    /* Host Busy */

/* SMBHOST_CNT register */
#define SMB_KILL                0x20    /* Kill */
#define SMB_START               0x10    /* Start */

/* register count for request_region
 * As we don't use SMB_PCOUNT, 20 is ok for SiS630 and SiS964
 */
#define SIS630_SMB_IOREGION     20

/* PCI address constants */
/* acpi base address register  */
#define SIS630_ACPI_BASE_REG    0x74
/* bios control register */
#define SIS630_BIOS_CTL_REG     0x40

/* Other settings */
#define MAX_TIMEOUT             500

/* SIS630 constants */
#define SIS630_QUICK            0x00
#define SIS630_BYTE             0x01
#define SIS630_BYTE_DATA        0x02
#define SIS630_WORD_DATA        0x03
#define SIS630_PCALL            0x04
#define SIS630_BLOCK_DATA       0x05

static struct pci_driver sis630_driver;

/* insmod parameters */
static bool high_clock;
static bool force;
module_param(high_clock, bool, 0);
MODULE_PARM_DESC(high_clock,
        "Set Host Master Clock to 56KHz (default 14KHz) (SIS630/730 only).");
module_param(force, bool, 0);
MODULE_PARM_DESC(force, "Forcibly enable the SIS630. DANGEROUS!");

/* SMBus base address */
static unsigned short smbus_base;

/* supported chips */
static int supported[] = {
        PCI_DEVICE_ID_SI_630,
        PCI_DEVICE_ID_SI_730,
        PCI_DEVICE_ID_SI_760,
        0 /* terminates the list */
};

static inline u8 sis630_read(u8 reg)
{
        return inb(smbus_base + reg);
}

static inline void sis630_write(u8 reg, u8 data)
{
        outb(data, smbus_base + reg);
}

static int sis630_transaction_start(struct i2c_adapter *adap, int size,
                                    u8 *oldclock)
{
        int temp;

        /* Make sure the SMBus host is ready to start transmitting. */
        temp = sis630_read(SMB_CNT);
        if ((temp & (SMB_PROBE | SMB_HOSTBUSY)) != 0x00) {
                dev_dbg(&adap->dev, "SMBus busy (%02x). Resetting...\n", temp);
                /* kill smbus transaction */
                sis630_write(SMBHOST_CNT, SMB_KILL);

                temp = sis630_read(SMB_CNT);
                if (temp & (SMB_PROBE | SMB_HOSTBUSY)) {
                        dev_dbg(&adap->dev, "Failed! (%02x)\n", temp);
                        return -EBUSY;
                } else {
                        dev_dbg(&adap->dev, "Successful!\n");
                }
        }

        /* save old clock, so we can prevent machine for hung */
        *oldclock = sis630_read(SMB_CNT);

        dev_dbg(&adap->dev, "saved clock 0x%02x\n", *oldclock);

        /* disable timeout interrupt,
         * set Host Master Clock to 56KHz if requested */
        if (high_clock)
                sis630_write(SMB_CNT, SMBCLK_SEL);
        else
                sis630_write(SMB_CNT, (*oldclock & ~MSTO_EN));

        /* clear all sticky bits */
        temp = sis630_read(SMB_STS);
        sis630_write(SMB_STS, temp & 0x1e);

        /* start the transaction by setting bit 4 and size */
        sis630_write(SMBHOST_CNT, SMB_START | (size & 0x07));

        return 0;
}

static int sis630_transaction_wait(struct i2c_adapter *adap, int size)
{
        int temp, result = 0, timeout = 0;

        /* We will always wait for a fraction of a second! */
        do {
                msleep(1);
                temp = sis630_read(SMB_STS);
                /* check if block transmitted */
                if (size == SIS630_BLOCK_DATA && (temp & BYTE_DONE_STS))
                        break;
        } while (!(temp & 0x0e) && (timeout++ < MAX_TIMEOUT));

        /* If the SMBus is still busy, we give up */
        if (timeout > MAX_TIMEOUT) {
                dev_dbg(&adap->dev, "SMBus Timeout!\n");
                result = -ETIMEDOUT;
        }

        if (temp & SMBERR_STS) {
                dev_dbg(&adap->dev, "Error: Failed bus transaction\n");
                result = -ENXIO;
        }

        if (temp & SMBCOL_STS) {
                dev_err(&adap->dev, "Bus collision!\n");
                result = -EAGAIN;
        }

        return result;
}

static void sis630_transaction_end(struct i2c_adapter *adap, u8 oldclock)
{
        /* clear all status "sticky" bits */
        sis630_write(SMB_STS, 0xFF);

        dev_dbg(&adap->dev,
                "SMB_CNT before clock restore 0x%02x\n", sis630_read(SMB_CNT));

        /*
         * restore old Host Master Clock if high_clock is set
         * and oldclock was not 56KHz
         */
        if (high_clock && !(oldclock & SMBCLK_SEL))
                sis630_write(SMB_CNT, sis630_read(SMB_CNT) & ~SMBCLK_SEL);

        dev_dbg(&adap->dev,
                "SMB_CNT after clock restore 0x%02x\n", sis630_read(SMB_CNT));
}

static int sis630_transaction(struct i2c_adapter *adap, int size)
{
        int result = 0;
        u8 oldclock = 0;

        result = sis630_transaction_start(adap, size, &oldclock);
        if (!result) {
                result = sis630_transaction_wait(adap, size);
                sis630_transaction_end(adap, oldclock);
        }

        return result;
}

static int sis630_block_data(struct i2c_adapter *adap,
                             union i2c_smbus_data *data, int read_write)
{
        int i, len = 0, rc = 0;
        u8 oldclock = 0;

        if (read_write == I2C_SMBUS_WRITE) {
                len = data->block[0];
                if (len < 0)
                        len = 0;
                else if (len > 32)
                        len = 32;
                sis630_write(SMB_COUNT, len);
                for (i = 1; i <= len; i++) {
                        dev_dbg(&adap->dev,
                                "set data 0x%02x\n", data->block[i]);
                        /* set data */
                        sis630_write(SMB_BYTE + (i - 1) % 8, data->block[i]);
                        if (i == 8 || (len < 8 && i == len)) {
                                dev_dbg(&adap->dev,
                                        "start trans len=%d i=%d\n", len, i);
                                /* first transaction */
                                rc = sis630_transaction_start(adap,
                                                SIS630_BLOCK_DATA, &oldclock);
                                if (rc)
                                        return rc;
                        } else if ((i - 1) % 8 == 7 || i == len) {
                                dev_dbg(&adap->dev,
                                        "trans_wait len=%d i=%d\n", len, i);
                                if (i > 8) {
                                        dev_dbg(&adap->dev,
                                                "clear smbary_sts"
                                                " len=%d i=%d\n", len, i);
                                        /*
                                           If this is not first transaction,
                                           we must clear sticky bit.
                                           clear SMBARY_STS
                                        */
                                        sis630_write(SMB_STS, BYTE_DONE_STS);
                                }
                                rc = sis630_transaction_wait(adap,
                                                SIS630_BLOCK_DATA);
                                if (rc) {
                                        dev_dbg(&adap->dev,
                                                "trans_wait failed\n");
                                        break;
                                }
                        }
                }
        } else {
                /* read request */
                data->block[0] = len = 0;
                rc = sis630_transaction_start(adap,
                                SIS630_BLOCK_DATA, &oldclock);
                if (rc)
                        return rc;
                do {
                        rc = sis630_transaction_wait(adap, SIS630_BLOCK_DATA);
                        if (rc) {
                                dev_dbg(&adap->dev, "trans_wait failed\n");
                                break;
                        }
                        /* if this first transaction then read byte count */
                        if (len == 0)
                                data->block[0] = sis630_read(SMB_COUNT);

                        /* just to be sure */
                        if (data->block[0] > 32)
                                data->block[0] = 32;

                        dev_dbg(&adap->dev,
                                "block data read len=0x%x\n", data->block[0]);

                        for (i = 0; i < 8 && len < data->block[0]; i++, len++) {
                                dev_dbg(&adap->dev,
                                        "read i=%d len=%d\n", i, len);
                                data->block[len + 1] = sis630_read(SMB_BYTE +
                                                                   i);
                        }

                        dev_dbg(&adap->dev,
                                "clear smbary_sts len=%d i=%d\n", len, i);

                        /* clear SMBARY_STS */
                        sis630_write(SMB_STS, BYTE_DONE_STS);
                } while (len < data->block[0]);
        }

        sis630_transaction_end(adap, oldclock);

        return rc;
}

/* Return negative errno on error. */
static s32 sis630_access(struct i2c_adapter *adap, u16 addr,
                         unsigned short flags, char read_write,
                         u8 command, int size, union i2c_smbus_data *data)
{
        int status;

        switch (size) {
        case I2C_SMBUS_QUICK:
                sis630_write(SMB_ADDR,
                             ((addr & 0x7f) << 1) | (read_write & 0x01));
                size = SIS630_QUICK;
                break;
        case I2C_SMBUS_BYTE:
                sis630_write(SMB_ADDR,
                             ((addr & 0x7f) << 1) | (read_write & 0x01));
                if (read_write == I2C_SMBUS_WRITE)
                        sis630_write(SMB_CMD, command);
                size = SIS630_BYTE;
                break;
        case I2C_SMBUS_BYTE_DATA:
                sis630_write(SMB_ADDR,
                             ((addr & 0x7f) << 1) | (read_write & 0x01));
                sis630_write(SMB_CMD, command);
                if (read_write == I2C_SMBUS_WRITE)
                        sis630_write(SMB_BYTE, data->byte);
                size = SIS630_BYTE_DATA;
                break;
        case I2C_SMBUS_PROC_CALL:
        case I2C_SMBUS_WORD_DATA:
                sis630_write(SMB_ADDR,
                             ((addr & 0x7f) << 1) | (read_write & 0x01));
                sis630_write(SMB_CMD, command);
                if (read_write == I2C_SMBUS_WRITE) {
                        sis630_write(SMB_BYTE, data->word & 0xff);
                        sis630_write(SMB_BYTE + 1, (data->word & 0xff00) >> 8);
                }
                size = (size == I2C_SMBUS_PROC_CALL ?
                        SIS630_PCALL : SIS630_WORD_DATA);
                break;
        case I2C_SMBUS_BLOCK_DATA:
                sis630_write(SMB_ADDR,
                             ((addr & 0x7f) << 1) | (read_write & 0x01));
                sis630_write(SMB_CMD, command);
                size = SIS630_BLOCK_DATA;
                return sis630_block_data(adap, data, read_write);
        default:
                dev_warn(&adap->dev, "Unsupported transaction %d\n", size);
                return -EOPNOTSUPP;
        }

        status = sis630_transaction(adap, size);
        if (status)
                return status;

        if ((size != SIS630_PCALL) &&
                ((read_write == I2C_SMBUS_WRITE) || (size == SIS630_QUICK))) {
                return 0;
        }

        switch (size) {
        case SIS630_BYTE:
        case SIS630_BYTE_DATA:
                data->byte = sis630_read(SMB_BYTE);
                break;
        case SIS630_PCALL:
        case SIS630_WORD_DATA:
                data->word = sis630_read(SMB_BYTE) +
                             (sis630_read(SMB_BYTE + 1) << 8);
                break;
        }

        return 0;
}

static u32 sis630_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_PROC_CALL | I2C_FUNC_SMBUS_BLOCK_DATA;
}

static int sis630_setup(struct pci_dev *sis630_dev)
{
        unsigned char b;
        struct pci_dev *dummy = NULL;
        int retval, i;
        /* acpi base address */
        unsigned short acpi_base;

        /* check for supported SiS devices */
        for (i = 0; supported[i] > 0; i++) {
                dummy = pci_get_device(PCI_VENDOR_ID_SI, supported[i], dummy);
                if (dummy)
                        break; /* found */
        }

        if (dummy) {
                pci_dev_put(dummy);
        } else if (force) {
                dev_err(&sis630_dev->dev,
                        "WARNING: Can't detect SIS630 compatible device, but "
                        "loading because of force option enabled\n");
        } else {
                return -ENODEV;
        }

        /*
           Enable ACPI first , so we can accsess reg 74-75
           in acpi io space and read acpi base addr
        */
        if (pci_read_config_byte(sis630_dev, SIS630_BIOS_CTL_REG, &b)) {
                dev_err(&sis630_dev->dev, "Error: Can't read bios ctl reg\n");
                retval = -ENODEV;
                goto exit;
        }
        /* if ACPI already enabled , do nothing */
        if (!(b & 0x80) &&
            pci_write_config_byte(sis630_dev, SIS630_BIOS_CTL_REG, b | 0x80)) {
                dev_err(&sis630_dev->dev, "Error: Can't enable ACPI\n");
                retval = -ENODEV;
                goto exit;
        }

        /* Determine the ACPI base address */
        if (pci_read_config_word(sis630_dev,
                                 SIS630_ACPI_BASE_REG, &acpi_base)) {
                dev_err(&sis630_dev->dev,
                        "Error: Can't determine ACPI base address\n");
                retval = -ENODEV;
                goto exit;
        }

        dev_dbg(&sis630_dev->dev, "ACPI base at 0x%04hx\n", acpi_base);

        if (supported[i] == PCI_DEVICE_ID_SI_760)
                smbus_base = acpi_base + 0xE0;
        else
                smbus_base = acpi_base + 0x80;

        dev_dbg(&sis630_dev->dev, "SMBus base at 0x%04hx\n", smbus_base);

        retval = acpi_check_region(smbus_base + SMB_STS, SIS630_SMB_IOREGION,
                                   sis630_driver.name);
        if (retval)
                goto exit;

        /* Everything is happy, let's grab the memory and set things up. */
        if (!request_region(smbus_base + SMB_STS, SIS630_SMB_IOREGION,
                            sis630_driver.name)) {
                dev_err(&sis630_dev->dev,
                        "I/O Region 0x%04x-0x%04x for SMBus already in use.\n",
                        smbus_base + SMB_STS,
                        smbus_base + SMB_STS + SIS630_SMB_IOREGION - 1);
                retval = -EBUSY;
                goto exit;
        }

        retval = 0;

exit:
        if (retval)
                smbus_base = 0;
        return retval;
}


static const struct i2c_algorithm smbus_algorithm = {
        .smbus_xfer     = sis630_access,
        .functionality  = sis630_func,
};

static struct i2c_adapter sis630_adapter = {
        .owner          = THIS_MODULE,
        .class          = I2C_CLASS_HWMON,
        .algo           = &smbus_algorithm,
        .retries        = 3
};

static const struct pci_device_id sis630_ids[] = {
        { PCI_DEVICE(PCI_VENDOR_ID_SI, PCI_DEVICE_ID_SI_503) },
        { PCI_DEVICE(PCI_VENDOR_ID_SI, PCI_DEVICE_ID_SI_LPC) },
        { PCI_DEVICE(PCI_VENDOR_ID_SI, PCI_DEVICE_ID_SI_964) },
        { 0, }
};

MODULE_DEVICE_TABLE(pci, sis630_ids);

static int sis630_probe(struct pci_dev *dev, const struct pci_device_id *id)
{
        int ret;

        if (sis630_setup(dev)) {
                dev_err(&dev->dev,
                        "SIS630 compatible bus not detected, "
                        "module not inserted.\n");
                return -ENODEV;
        }

        /* set up the sysfs linkage to our parent device */
        sis630_adapter.dev.parent = &dev->dev;

        snprintf(sis630_adapter.name, sizeof(sis630_adapter.name),
                 "SMBus SIS630 adapter at %04x", smbus_base + SMB_STS);

        ret = i2c_add_adapter(&sis630_adapter);
        if (ret)
                goto release_region;

        return 0;

release_region:
        release_region(smbus_base + SMB_STS, SIS630_SMB_IOREGION);
        return ret;
}

static void sis630_remove(struct pci_dev *dev)
{
        if (smbus_base) {
                i2c_del_adapter(&sis630_adapter);
                release_region(smbus_base + SMB_STS, SIS630_SMB_IOREGION);
                smbus_base = 0;
        }
}


static struct pci_driver sis630_driver = {
        .name           = "sis630_smbus",
        .id_table       = sis630_ids,
        .probe          = sis630_probe,
        .remove         = sis630_remove,
};

module_pci_driver(sis630_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alexander Malysh <amalysh@web.de>");
MODULE_DESCRIPTION("SIS630 SMBus driver");