spi-xcomm.c

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/*
 * Analog Devices AD-FMCOMMS1-EBZ board I2C-SPI bridge driver
 *
 * Copyright 2012 Analog Devices Inc.
 * Author: Lars-Peter Clausen <[email protected]>
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/spi/spi.h>
#include <asm/unaligned.h>

#define SPI_XCOMM_SETTINGS_LEN_OFFSET       10
#define SPI_XCOMM_SETTINGS_3WIRE        BIT(6)
#define SPI_XCOMM_SETTINGS_CS_HIGH      BIT(5)
#define SPI_XCOMM_SETTINGS_SAMPLE_END       BIT(4)
#define SPI_XCOMM_SETTINGS_CPHA         BIT(3)
#define SPI_XCOMM_SETTINGS_CPOL         BIT(2)
#define SPI_XCOMM_SETTINGS_CLOCK_DIV_MASK   0x3
#define SPI_XCOMM_SETTINGS_CLOCK_DIV_64     0x2
#define SPI_XCOMM_SETTINGS_CLOCK_DIV_16     0x1
#define SPI_XCOMM_SETTINGS_CLOCK_DIV_4      0x0

#define SPI_XCOMM_CMD_UPDATE_CONFIG 0x03
#define SPI_XCOMM_CMD_WRITE     0x04

#define SPI_XCOMM_CLOCK 48000000

struct spi_xcomm {
    struct i2c_client *i2c;

    uint16_t settings;
    uint16_t chipselect;

    unsigned int current_speed;

    uint8_t buf[63];
};

static int spi_xcomm_sync_config(struct spi_xcomm *spi_xcomm, unsigned int len)
{
    uint16_t settings;
    uint8_t *buf = spi_xcomm->buf;

    settings = spi_xcomm->settings;
    settings |= len << SPI_XCOMM_SETTINGS_LEN_OFFSET;

    buf[0] = SPI_XCOMM_CMD_UPDATE_CONFIG;
    put_unaligned_be16(settings, &buf[1]);
    put_unaligned_be16(spi_xcomm->chipselect, &buf[3]);

    return i2c_master_send(spi_xcomm->i2c, buf, 5);
}

static void spi_xcomm_chipselect(struct spi_xcomm *spi_xcomm,
    struct spi_device *spi, int is_active)
{
    unsigned long cs = spi->chip_select;
    uint16_t chipselect = spi_xcomm->chipselect;

    if (is_active)
        chipselect |= BIT(cs);
    else
        chipselect &= ~BIT(cs);

    spi_xcomm->chipselect = chipselect;
}

static int spi_xcomm_setup_transfer(struct spi_xcomm *spi_xcomm,
    struct spi_device *spi, struct spi_transfer *t, unsigned int *settings)
{
    unsigned int speed;

    if ((t->bits_per_word && t->bits_per_word != 8) || t->len > 62)
        return -EINVAL;

    speed = t->speed_hz ? t->speed_hz : spi->max_speed_hz;

    if (speed != spi_xcomm->current_speed) {
        unsigned int divider = DIV_ROUND_UP(SPI_XCOMM_CLOCK, speed);
        if (divider >= 64)
            *settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_64;
        else if (divider >= 16)
            *settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_16;
        else
            *settings |= SPI_XCOMM_SETTINGS_CLOCK_DIV_4;

        spi_xcomm->current_speed = speed;
    }

    if (spi->mode & SPI_CPOL)
        *settings |= SPI_XCOMM_SETTINGS_CPOL;
    else
        *settings &= ~SPI_XCOMM_SETTINGS_CPOL;

    if (spi->mode & SPI_CPHA)
        *settings &= ~SPI_XCOMM_SETTINGS_CPHA;
    else
        *settings |= SPI_XCOMM_SETTINGS_CPHA;

    if (spi->mode & SPI_3WIRE)
        *settings |= SPI_XCOMM_SETTINGS_3WIRE;
    else
        *settings &= ~SPI_XCOMM_SETTINGS_3WIRE;

    return 0;
}

static int spi_xcomm_txrx_bufs(struct spi_xcomm *spi_xcomm,
    struct spi_device *spi, struct spi_transfer *t)
{
    int ret;

    if (t->tx_buf) {
        spi_xcomm->buf[0] = SPI_XCOMM_CMD_WRITE;
        memcpy(spi_xcomm->buf + 1, t->tx_buf, t->len);

        ret = i2c_master_send(spi_xcomm->i2c, spi_xcomm->buf, t->len + 1);
        if (ret < 0)
            return ret;
        else if (ret != t->len + 1)
            return -EIO;
    } else if (t->rx_buf) {
        ret = i2c_master_recv(spi_xcomm->i2c, t->rx_buf, t->len);
        if (ret < 0)
            return ret;
        else if (ret != t->len)
            return -EIO;
    }

    return t->len;
}

static int spi_xcomm_transfer_one(struct spi_master *master,
    struct spi_message *msg)
{
    struct spi_xcomm *spi_xcomm = spi_master_get_devdata(master);
    unsigned int settings = spi_xcomm->settings;
    struct spi_device *spi = msg->spi;
    unsigned cs_change = 0;
    struct spi_transfer *t;
    bool is_first = true;
    int status = 0;
    bool is_last;

    is_first = true;

    spi_xcomm_chipselect(spi_xcomm, spi, true);

    list_for_each_entry(t, &msg->transfers, transfer_list) {

        if (!t->tx_buf && !t->rx_buf && t->len) {
            status = -EINVAL;
            break;
        }

        status = spi_xcomm_setup_transfer(spi_xcomm, spi, t, &settings);
        if (status < 0)
            break;

        is_last = list_is_last(&t->transfer_list, &msg->transfers);
        cs_change = t->cs_change;

        if (cs_change ^ is_last)
            settings |= BIT(5);
        else
            settings &= ~BIT(5);

        if (t->rx_buf) {
            spi_xcomm->settings = settings;
            status = spi_xcomm_sync_config(spi_xcomm, t->len);
            if (status < 0)
                break;
        } else if (settings != spi_xcomm->settings || is_first) {
            spi_xcomm->settings = settings;
            status = spi_xcomm_sync_config(spi_xcomm, 0);
            if (status < 0)
                break;
        }

        if (t->len) {
            status = spi_xcomm_txrx_bufs(spi_xcomm, spi, t);

            if (status < 0)
                break;

            if (status > 0)
                msg->actual_length += status;
        }
        status = 0;

        if (t->delay_usecs)
            udelay(t->delay_usecs);

        is_first = false;
    }

    if (status != 0 || !cs_change)
        spi_xcomm_chipselect(spi_xcomm, spi, false);

    msg->status = status;
    spi_finalize_current_message(master);

    return status;
}

static int spi_xcomm_setup(struct spi_device *spi)
{
    if (spi->bits_per_word != 8)
        return -EINVAL;

    return 0;
}

static int __devinit spi_xcomm_probe(struct i2c_client *i2c,
    const struct i2c_device_id *id)
{
    struct spi_xcomm *spi_xcomm;
    struct spi_master *master;
    int ret;

    master = spi_alloc_master(&i2c->dev, sizeof(*spi_xcomm));
    if (!master)
        return -ENOMEM;

    spi_xcomm = spi_master_get_devdata(master);
    spi_xcomm->i2c = i2c;

    master->num_chipselect = 16;
    master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_3WIRE;
    master->flags = SPI_MASTER_HALF_DUPLEX;
    master->setup = spi_xcomm_setup;
    master->transfer_one_message = spi_xcomm_transfer_one;
    master->dev.of_node = i2c->dev.of_node;
    i2c_set_clientdata(i2c, master);

    ret = spi_register_master(master);
    if (ret < 0)
        spi_master_put(master);

    return ret;
}

static int __devexit spi_xcomm_remove(struct i2c_client *i2c)
{
    struct spi_master *master = i2c_get_clientdata(i2c);

    spi_unregister_master(master);

    return 0;
}

static const struct i2c_device_id spi_xcomm_ids[] = {
    { "spi-xcomm" },
    { },
};

static struct i2c_driver spi_xcomm_driver = {
    .driver = {
        .name   = "spi-xcomm",
        .owner  = THIS_MODULE,
    },
    .id_table   = spi_xcomm_ids,
    .probe      = spi_xcomm_probe,
    .remove     = __devexit_p(spi_xcomm_remove),
};
module_i2c_driver(spi_xcomm_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Lars-Peter Clausen <[email protected]>");
MODULE_DESCRIPTION("Analog Devices AD-FMCOMMS1-EBZ board I2C-SPI bridge driver");