// SPDX-License-Identifier: GPL-2.0-only
/*
 * Driver for the Diolan u2c-12 USB-I2C adapter
 *
 * Copyright (c) 2010-2011 Ericsson AB
 *
 * Derived from:
 *  i2c-tiny-usb.c
 *  Copyright (C) 2006-2007 Till Harbaum (Till@Harbaum.org)
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/usb.h>
#include <linux/i2c.h>

#define DRIVER_NAME             "i2c-diolan-u2c"

#define USB_VENDOR_ID_DIOLAN            0x0abf
#define USB_DEVICE_ID_DIOLAN_U2C        0x3370


/* commands via USB, must match command ids in the firmware */
#define CMD_I2C_READ            0x01
#define CMD_I2C_WRITE           0x02
#define CMD_I2C_SCAN            0x03    /* Returns list of detected devices */
#define CMD_I2C_RELEASE_SDA     0x04
#define CMD_I2C_RELEASE_SCL     0x05
#define CMD_I2C_DROP_SDA        0x06
#define CMD_I2C_DROP_SCL        0x07
#define CMD_I2C_READ_SDA        0x08
#define CMD_I2C_READ_SCL        0x09
#define CMD_GET_FW_VERSION      0x0a
#define CMD_GET_SERIAL          0x0b
#define CMD_I2C_START           0x0c
#define CMD_I2C_STOP            0x0d
#define CMD_I2C_REPEATED_START  0x0e
#define CMD_I2C_PUT_BYTE        0x0f
#define CMD_I2C_GET_BYTE        0x10
#define CMD_I2C_PUT_ACK         0x11
#define CMD_I2C_GET_ACK         0x12
#define CMD_I2C_PUT_BYTE_ACK    0x13
#define CMD_I2C_GET_BYTE_ACK    0x14
#define CMD_I2C_SET_SPEED       0x1b
#define CMD_I2C_GET_SPEED       0x1c
#define CMD_I2C_SET_CLK_SYNC    0x24
#define CMD_I2C_GET_CLK_SYNC    0x25
#define CMD_I2C_SET_CLK_SYNC_TO 0x26
#define CMD_I2C_GET_CLK_SYNC_TO 0x27

#define RESP_OK                 0x00
#define RESP_FAILED             0x01
#define RESP_BAD_MEMADDR        0x04
#define RESP_DATA_ERR           0x05
#define RESP_NOT_IMPLEMENTED    0x06
#define RESP_NACK               0x07
#define RESP_TIMEOUT            0x09

#define U2C_I2C_SPEED_FAST      0       /* 400 kHz */
#define U2C_I2C_SPEED_STD       1       /* 100 kHz */
#define U2C_I2C_SPEED_2KHZ      242     /* 2 kHz, minimum speed */
#define U2C_I2C_SPEED(f)        ((DIV_ROUND_UP(1000000, (f)) - 10) / 2 + 1)

#define U2C_I2C_FREQ(s)         (1000000 / (2 * (s - 1) + 10))

#define DIOLAN_USB_TIMEOUT      100     /* in ms */
#define DIOLAN_SYNC_TIMEOUT     20      /* in ms */

#define DIOLAN_OUTBUF_LEN       128
#define DIOLAN_FLUSH_LEN        (DIOLAN_OUTBUF_LEN - 4)
#define DIOLAN_INBUF_LEN        256     /* Maximum supported receive length */

/* Structure to hold all of our device specific stuff */
struct i2c_diolan_u2c {
        u8 obuffer[DIOLAN_OUTBUF_LEN];  /* output buffer */
        u8 ibuffer[DIOLAN_INBUF_LEN];   /* input buffer */
        int ep_in, ep_out;              /* Endpoints    */
        struct usb_device *usb_dev;     /* the usb device for this device */
        struct usb_interface *interface;/* the interface for this device */
        struct i2c_adapter adapter;     /* i2c related things */
        int olen;                       /* Output buffer length */
        int ocount;                     /* Number of enqueued messages */
};

static uint frequency = I2C_MAX_STANDARD_MODE_FREQ;     /* I2C clock frequency in Hz */

module_param(frequency, uint, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(frequency, "I2C clock frequency in hertz");

/* usb layer */

/* Send command to device, and get response. */
static int diolan_usb_transfer(struct i2c_diolan_u2c *dev)
{
        int ret = 0;
        int actual;
        int i;

        if (!dev->olen || !dev->ocount)
                return -EINVAL;

        ret = usb_bulk_msg(dev->usb_dev,
                           usb_sndbulkpipe(dev->usb_dev, dev->ep_out),
                           dev->obuffer, dev->olen, &actual,
                           DIOLAN_USB_TIMEOUT);
        if (!ret) {
                for (i = 0; i < dev->ocount; i++) {
                        int tmpret;

                        tmpret = usb_bulk_msg(dev->usb_dev,
                                              usb_rcvbulkpipe(dev->usb_dev,
                                                              dev->ep_in),
                                              dev->ibuffer,
                                              sizeof(dev->ibuffer), &actual,
                                              DIOLAN_USB_TIMEOUT);
                        /*
                         * Stop command processing if a previous command
                         * returned an error.
                         * Note that we still need to retrieve all messages.
                         */
                        if (ret < 0)
                                continue;
                        ret = tmpret;
                        if (ret == 0 && actual > 0) {
                                switch (dev->ibuffer[actual - 1]) {
                                case RESP_NACK:
                                        /*
                                         * Return ENXIO if NACK was received as
                                         * response to the address phase,
                                         * EIO otherwise
                                         */
                                        ret = i == 1 ? -ENXIO : -EIO;
                                        break;
                                case RESP_TIMEOUT:
                                        ret = -ETIMEDOUT;
                                        break;
                                case RESP_OK:
                                        /* strip off return code */
                                        ret = actual - 1;
                                        break;
                                default:
                                        ret = -EIO;
                                        break;
                                }
                        }
                }
        }
        dev->olen = 0;
        dev->ocount = 0;
        return ret;
}

static int diolan_write_cmd(struct i2c_diolan_u2c *dev, bool flush)
{
        if (flush || dev->olen >= DIOLAN_FLUSH_LEN)
                return diolan_usb_transfer(dev);
        return 0;
}

/* Send command (no data) */
static int diolan_usb_cmd(struct i2c_diolan_u2c *dev, u8 command, bool flush)
{
        dev->obuffer[dev->olen++] = command;
        dev->ocount++;
        return diolan_write_cmd(dev, flush);
}

/* Send command with one byte of data */
static int diolan_usb_cmd_data(struct i2c_diolan_u2c *dev, u8 command, u8 data,
                               bool flush)
{
        dev->obuffer[dev->olen++] = command;
        dev->obuffer[dev->olen++] = data;
        dev->ocount++;
        return diolan_write_cmd(dev, flush);
}

/* Send command with two bytes of data */
static int diolan_usb_cmd_data2(struct i2c_diolan_u2c *dev, u8 command, u8 d1,
                                u8 d2, bool flush)
{
        dev->obuffer[dev->olen++] = command;
        dev->obuffer[dev->olen++] = d1;
        dev->obuffer[dev->olen++] = d2;
        dev->ocount++;
        return diolan_write_cmd(dev, flush);
}

/*
 * Flush input queue.
 * If we don't do this at startup and the controller has queued up
 * messages which were not retrieved, it will stop responding
 * at some point.
 */
static void diolan_flush_input(struct i2c_diolan_u2c *dev)
{
        int i;

        for (i = 0; i < 10; i++) {
                int actual = 0;
                int ret;

                ret = usb_bulk_msg(dev->usb_dev,
                                   usb_rcvbulkpipe(dev->usb_dev, dev->ep_in),
                                   dev->ibuffer, sizeof(dev->ibuffer), &actual,
                                   DIOLAN_USB_TIMEOUT);
                if (ret < 0 || actual == 0)
                        break;
        }
        if (i == 10)
                dev_err(&dev->interface->dev, "Failed to flush input buffer\n");
}

static int diolan_i2c_start(struct i2c_diolan_u2c *dev)
{
        return diolan_usb_cmd(dev, CMD_I2C_START, false);
}

static int diolan_i2c_repeated_start(struct i2c_diolan_u2c *dev)
{
        return diolan_usb_cmd(dev, CMD_I2C_REPEATED_START, false);
}

static int diolan_i2c_stop(struct i2c_diolan_u2c *dev)
{
        return diolan_usb_cmd(dev, CMD_I2C_STOP, true);
}

static int diolan_i2c_get_byte_ack(struct i2c_diolan_u2c *dev, bool ack,
                                   u8 *byte)
{
        int ret;

        ret = diolan_usb_cmd_data(dev, CMD_I2C_GET_BYTE_ACK, ack, true);
        if (ret > 0)
                *byte = dev->ibuffer[0];
        else if (ret == 0)
                ret = -EIO;

        return ret;
}

static int diolan_i2c_put_byte_ack(struct i2c_diolan_u2c *dev, u8 byte)
{
        return diolan_usb_cmd_data(dev, CMD_I2C_PUT_BYTE_ACK, byte, false);
}

static int diolan_set_speed(struct i2c_diolan_u2c *dev, u8 speed)
{
        return diolan_usb_cmd_data(dev, CMD_I2C_SET_SPEED, speed, true);
}

/* Enable or disable clock synchronization (stretching) */
static int diolan_set_clock_synch(struct i2c_diolan_u2c *dev, bool enable)
{
        return diolan_usb_cmd_data(dev, CMD_I2C_SET_CLK_SYNC, enable, true);
}

/* Set clock synchronization timeout in ms */
static int diolan_set_clock_synch_timeout(struct i2c_diolan_u2c *dev, int ms)
{
        int to_val = ms * 10;

        return diolan_usb_cmd_data2(dev, CMD_I2C_SET_CLK_SYNC_TO,
                                    to_val & 0xff, (to_val >> 8) & 0xff, true);
}

static void diolan_fw_version(struct i2c_diolan_u2c *dev)
{
        int ret;

        ret = diolan_usb_cmd(dev, CMD_GET_FW_VERSION, true);
        if (ret >= 2)
                dev_info(&dev->interface->dev,
                         "Diolan U2C firmware version %u.%u\n",
                         (unsigned int)dev->ibuffer[0],
                         (unsigned int)dev->ibuffer[1]);
}

static void diolan_get_serial(struct i2c_diolan_u2c *dev)
{
        int ret;
        u32 serial;

        ret = diolan_usb_cmd(dev, CMD_GET_SERIAL, true);
        if (ret >= 4) {
                serial = le32_to_cpu(*(u32 *)dev->ibuffer);
                dev_info(&dev->interface->dev,
                         "Diolan U2C serial number %u\n", serial);
        }
}

static int diolan_init(struct i2c_diolan_u2c *dev)
{
        int speed, ret;

        if (frequency >= 2 * I2C_MAX_STANDARD_MODE_FREQ) {
                speed = U2C_I2C_SPEED_FAST;
                frequency = I2C_MAX_FAST_MODE_FREQ;
        } else if (frequency >= I2C_MAX_STANDARD_MODE_FREQ || frequency == 0) {
                speed = U2C_I2C_SPEED_STD;
                frequency = I2C_MAX_STANDARD_MODE_FREQ;
        } else {
                speed = U2C_I2C_SPEED(frequency);
                if (speed > U2C_I2C_SPEED_2KHZ)
                        speed = U2C_I2C_SPEED_2KHZ;
                frequency = U2C_I2C_FREQ(speed);
        }

        dev_info(&dev->interface->dev,
                 "Diolan U2C at USB bus %03d address %03d speed %d Hz\n",
                 dev->usb_dev->bus->busnum, dev->usb_dev->devnum, frequency);

        diolan_flush_input(dev);
        diolan_fw_version(dev);
        diolan_get_serial(dev);

        /* Set I2C speed */
        ret = diolan_set_speed(dev, speed);
        if (ret < 0)
                return ret;

        /* Configure I2C clock synchronization */
        ret = diolan_set_clock_synch(dev, speed != U2C_I2C_SPEED_FAST);
        if (ret < 0)
                return ret;

        if (speed != U2C_I2C_SPEED_FAST)
                ret = diolan_set_clock_synch_timeout(dev, DIOLAN_SYNC_TIMEOUT);

        return ret;
}

/* i2c layer */

static int diolan_usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
                           int num)
{
        struct i2c_diolan_u2c *dev = i2c_get_adapdata(adapter);
        struct i2c_msg *pmsg;
        int i, j;
        int ret, sret;

        ret = diolan_i2c_start(dev);
        if (ret < 0)
                return ret;

        for (i = 0; i < num; i++) {
                pmsg = &msgs[i];
                if (i) {
                        ret = diolan_i2c_repeated_start(dev);
                        if (ret < 0)
                                goto abort;
                }
                ret = diolan_i2c_put_byte_ack(dev,
                                              i2c_8bit_addr_from_msg(pmsg));
                if (ret < 0)
                        goto abort;
                if (pmsg->flags & I2C_M_RD) {
                        for (j = 0; j < pmsg->len; j++) {
                                u8 byte;
                                bool ack = j < pmsg->len - 1;

                                /*
                                 * Don't send NACK if this is the first byte
                                 * of a SMBUS_BLOCK message.
                                 */
                                if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN))
                                        ack = true;

                                ret = diolan_i2c_get_byte_ack(dev, ack, &byte);
                                if (ret < 0)
                                        goto abort;
                                /*
                                 * Adjust count if first received byte is length
                                 */
                                if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN)) {
                                        if (byte == 0
                                            || byte > I2C_SMBUS_BLOCK_MAX) {
                                                ret = -EPROTO;
                                                goto abort;
                                        }
                                        pmsg->len += byte;
                                }
                                pmsg->buf[j] = byte;
                        }
                } else {
                        for (j = 0; j < pmsg->len; j++) {
                                ret = diolan_i2c_put_byte_ack(dev,
                                                              pmsg->buf[j]);
                                if (ret < 0)
                                        goto abort;
                        }
                }
        }
        ret = num;
abort:
        sret = diolan_i2c_stop(dev);
        if (sret < 0 && ret >= 0)
                ret = sret;
        return ret;
}

/*
 * Return list of supported functionality.
 */
static u32 diolan_usb_func(struct i2c_adapter *a)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
               I2C_FUNC_SMBUS_READ_BLOCK_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL;
}

static const struct i2c_algorithm diolan_usb_algorithm = {
        .xfer = diolan_usb_xfer,
        .functionality = diolan_usb_func,
};

/* device layer */

static const struct usb_device_id diolan_u2c_table[] = {
        { USB_DEVICE(USB_VENDOR_ID_DIOLAN, USB_DEVICE_ID_DIOLAN_U2C) },
        { }
};

MODULE_DEVICE_TABLE(usb, diolan_u2c_table);

static void diolan_u2c_free(struct i2c_diolan_u2c *dev)
{
        usb_put_dev(dev->usb_dev);
        kfree(dev);
}

static int diolan_u2c_probe(struct usb_interface *interface,
                            const struct usb_device_id *id)
{
        struct usb_host_interface *hostif = interface->cur_altsetting;
        struct i2c_diolan_u2c *dev;
        int ret;

        if (hostif->desc.bInterfaceNumber != 0
            || hostif->desc.bNumEndpoints < 2)
                return -ENODEV;

        /* allocate memory for our device state and initialize it */
        dev = kzalloc_obj(*dev);
        if (dev == NULL) {
                ret = -ENOMEM;
                goto error;
        }
        dev->ep_out = hostif->endpoint[0].desc.bEndpointAddress;
        dev->ep_in = hostif->endpoint[1].desc.bEndpointAddress;

        dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
        dev->interface = interface;

        /* save our data pointer in this interface device */
        usb_set_intfdata(interface, dev);

        /* setup i2c adapter description */
        dev->adapter.owner = THIS_MODULE;
        dev->adapter.class = I2C_CLASS_HWMON;
        dev->adapter.algo = &diolan_usb_algorithm;
        i2c_set_adapdata(&dev->adapter, dev);
        snprintf(dev->adapter.name, sizeof(dev->adapter.name),
                 DRIVER_NAME " at bus %03d device %03d",
                 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);

        dev->adapter.dev.parent = &dev->interface->dev;

        /* initialize diolan i2c interface */
        ret = diolan_init(dev);
        if (ret < 0) {
                dev_err(&interface->dev, "failed to initialize adapter\n");
                goto error_free;
        }

        /* and finally attach to i2c layer */
        ret = i2c_add_adapter(&dev->adapter);
        if (ret < 0)
                goto error_free;

        dev_dbg(&interface->dev, "connected " DRIVER_NAME "\n");

        return 0;

error_free:
        usb_set_intfdata(interface, NULL);
        diolan_u2c_free(dev);
error:
        return ret;
}

static void diolan_u2c_disconnect(struct usb_interface *interface)
{
        struct i2c_diolan_u2c *dev = usb_get_intfdata(interface);

        i2c_del_adapter(&dev->adapter);
        usb_set_intfdata(interface, NULL);
        diolan_u2c_free(dev);

        dev_dbg(&interface->dev, "disconnected\n");
}

static struct usb_driver diolan_u2c_driver = {
        .name = DRIVER_NAME,
        .probe = diolan_u2c_probe,
        .disconnect = diolan_u2c_disconnect,
        .id_table = diolan_u2c_table,
};

module_usb_driver(diolan_u2c_driver);

MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
MODULE_DESCRIPTION(DRIVER_NAME " driver");
MODULE_LICENSE("GPL");