spi-orion.c

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/*
 * Marvell Orion SPI controller driver
 *
 * Author: Shadi Ammouri <[email protected]>
 * Copyright (C) 2007-2008 Marvell Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/err.h>
#include <linux/io.h>
#include <linux/spi/spi.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/clk.h>
#include <asm/unaligned.h>

#define DRIVER_NAME         "orion_spi"

#define ORION_NUM_CHIPSELECTS       1 /* only one slave is supported*/
#define ORION_SPI_WAIT_RDY_MAX_LOOP 2000 /* in usec */

#define ORION_SPI_IF_CTRL_REG       0x00
#define ORION_SPI_IF_CONFIG_REG     0x04
#define ORION_SPI_DATA_OUT_REG      0x08
#define ORION_SPI_DATA_IN_REG       0x0c
#define ORION_SPI_INT_CAUSE_REG     0x10

#define ORION_SPI_IF_8_16_BIT_MODE  (1 << 5)
#define ORION_SPI_CLK_PRESCALE_MASK 0x1F

struct orion_spi {
    struct spi_master   *master;
    void __iomem        *base;
    unsigned int        max_speed;
    unsigned int        min_speed;
    struct clk              *clk;
};

static inline void __iomem *spi_reg(struct orion_spi *orion_spi, u32 reg)
{
    return orion_spi->base + reg;
}

static inline void
orion_spi_setbits(struct orion_spi *orion_spi, u32 reg, u32 mask)
{
    void __iomem *reg_addr = spi_reg(orion_spi, reg);
    u32 val;

    val = readl(reg_addr);
    val |= mask;
    writel(val, reg_addr);
}

static inline void
orion_spi_clrbits(struct orion_spi *orion_spi, u32 reg, u32 mask)
{
    void __iomem *reg_addr = spi_reg(orion_spi, reg);
    u32 val;

    val = readl(reg_addr);
    val &= ~mask;
    writel(val, reg_addr);
}

static int orion_spi_set_transfer_size(struct orion_spi *orion_spi, int size)
{
    if (size == 16) {
        orion_spi_setbits(orion_spi, ORION_SPI_IF_CONFIG_REG,
                  ORION_SPI_IF_8_16_BIT_MODE);
    } else if (size == 8) {
        orion_spi_clrbits(orion_spi, ORION_SPI_IF_CONFIG_REG,
                  ORION_SPI_IF_8_16_BIT_MODE);
    } else {
        pr_debug("Bad bits per word value %d (only 8 or 16 are "
             "allowed).\n", size);
        return -EINVAL;
    }

    return 0;
}

static int orion_spi_baudrate_set(struct spi_device *spi, unsigned int speed)
{
    u32 tclk_hz;
    u32 rate;
    u32 prescale;
    u32 reg;
    struct orion_spi *orion_spi;

    orion_spi = spi_master_get_devdata(spi->master);

    tclk_hz = clk_get_rate(orion_spi->clk);

    /*
     * the supported rates are: 4,6,8...30
     * round up as we look for equal or less speed
     */
    rate = DIV_ROUND_UP(tclk_hz, speed);
    rate = roundup(rate, 2);

    /* check if requested speed is too small */
    if (rate > 30)
        return -EINVAL;

    if (rate < 4)
        rate = 4;

    /* Convert the rate to SPI clock divisor value. */
    prescale = 0x10 + rate/2;

    reg = readl(spi_reg(orion_spi, ORION_SPI_IF_CONFIG_REG));
    reg = ((reg & ~ORION_SPI_CLK_PRESCALE_MASK) | prescale);
    writel(reg, spi_reg(orion_spi, ORION_SPI_IF_CONFIG_REG));

    return 0;
}

/*
 * called only when no transfer is active on the bus
 */
static int
orion_spi_setup_transfer(struct spi_device *spi, struct spi_transfer *t)
{
    struct orion_spi *orion_spi;
    unsigned int speed = spi->max_speed_hz;
    unsigned int bits_per_word = spi->bits_per_word;
    int rc;

    orion_spi = spi_master_get_devdata(spi->master);

    if ((t != NULL) && t->speed_hz)
        speed = t->speed_hz;

    if ((t != NULL) && t->bits_per_word)
        bits_per_word = t->bits_per_word;

    rc = orion_spi_baudrate_set(spi, speed);
    if (rc)
        return rc;

    return orion_spi_set_transfer_size(orion_spi, bits_per_word);
}

static void orion_spi_set_cs(struct orion_spi *orion_spi, int enable)
{
    if (enable)
        orion_spi_setbits(orion_spi, ORION_SPI_IF_CTRL_REG, 0x1);
    else
        orion_spi_clrbits(orion_spi, ORION_SPI_IF_CTRL_REG, 0x1);
}

static inline int orion_spi_wait_till_ready(struct orion_spi *orion_spi)
{
    int i;

    for (i = 0; i < ORION_SPI_WAIT_RDY_MAX_LOOP; i++) {
        if (readl(spi_reg(orion_spi, ORION_SPI_INT_CAUSE_REG)))
            return 1;
        else
            udelay(1);
    }

    return -1;
}

static inline int
orion_spi_write_read_8bit(struct spi_device *spi,
              const u8 **tx_buf, u8 **rx_buf)
{
    void __iomem *tx_reg, *rx_reg, *int_reg;
    struct orion_spi *orion_spi;

    orion_spi = spi_master_get_devdata(spi->master);
    tx_reg = spi_reg(orion_spi, ORION_SPI_DATA_OUT_REG);
    rx_reg = spi_reg(orion_spi, ORION_SPI_DATA_IN_REG);
    int_reg = spi_reg(orion_spi, ORION_SPI_INT_CAUSE_REG);

    /* clear the interrupt cause register */
    writel(0x0, int_reg);

    if (tx_buf && *tx_buf)
        writel(*(*tx_buf)++, tx_reg);
    else
        writel(0, tx_reg);

    if (orion_spi_wait_till_ready(orion_spi) < 0) {
        dev_err(&spi->dev, "TXS timed out\n");
        return -1;
    }

    if (rx_buf && *rx_buf)
        *(*rx_buf)++ = readl(rx_reg);

    return 1;
}

static inline int
orion_spi_write_read_16bit(struct spi_device *spi,
               const u16 **tx_buf, u16 **rx_buf)
{
    void __iomem *tx_reg, *rx_reg, *int_reg;
    struct orion_spi *orion_spi;

    orion_spi = spi_master_get_devdata(spi->master);
    tx_reg = spi_reg(orion_spi, ORION_SPI_DATA_OUT_REG);
    rx_reg = spi_reg(orion_spi, ORION_SPI_DATA_IN_REG);
    int_reg = spi_reg(orion_spi, ORION_SPI_INT_CAUSE_REG);

    /* clear the interrupt cause register */
    writel(0x0, int_reg);

    if (tx_buf && *tx_buf)
        writel(__cpu_to_le16(get_unaligned((*tx_buf)++)), tx_reg);
    else
        writel(0, tx_reg);

    if (orion_spi_wait_till_ready(orion_spi) < 0) {
        dev_err(&spi->dev, "TXS timed out\n");
        return -1;
    }

    if (rx_buf && *rx_buf)
        put_unaligned(__le16_to_cpu(readl(rx_reg)), (*rx_buf)++);

    return 1;
}

static unsigned int
orion_spi_write_read(struct spi_device *spi, struct spi_transfer *xfer)
{
    struct orion_spi *orion_spi;
    unsigned int count;
    int word_len;

    orion_spi = spi_master_get_devdata(spi->master);
    word_len = spi->bits_per_word;
    count = xfer->len;

    if (word_len == 8) {
        const u8 *tx = xfer->tx_buf;
        u8 *rx = xfer->rx_buf;

        do {
            if (orion_spi_write_read_8bit(spi, &tx, &rx) < 0)
                goto out;
            count--;
        } while (count);
    } else if (word_len == 16) {
        const u16 *tx = xfer->tx_buf;
        u16 *rx = xfer->rx_buf;

        do {
            if (orion_spi_write_read_16bit(spi, &tx, &rx) < 0)
                goto out;
            count -= 2;
        } while (count);
    }

out:
    return xfer->len - count;
}


static int orion_spi_transfer_one_message(struct spi_master *master,
                       struct spi_message *m)
{
    struct orion_spi *orion_spi = spi_master_get_devdata(master);
    struct spi_device *spi = m->spi;
    struct spi_transfer *t = NULL;
    int par_override = 0;
    int status = 0;
    int cs_active = 0;

    /* Load defaults */
    status = orion_spi_setup_transfer(spi, NULL);

    if (status < 0)
        goto msg_done;

    list_for_each_entry(t, &m->transfers, transfer_list) {
        /* make sure buffer length is even when working in 16
         * bit mode*/
        if ((t->bits_per_word == 16) && (t->len & 1)) {
            dev_err(&spi->dev,
                "message rejected : "
                "odd data length %d while in 16 bit mode\n",
                t->len);
            status = -EIO;
            goto msg_done;
        }

        if (t->speed_hz && t->speed_hz < orion_spi->min_speed) {
            dev_err(&spi->dev,
                "message rejected : "
                "device min speed (%d Hz) exceeds "
                "required transfer speed (%d Hz)\n",
                orion_spi->min_speed, t->speed_hz);
            status = -EIO;
            goto msg_done;
        }

        if (par_override || t->speed_hz || t->bits_per_word) {
            par_override = 1;
            status = orion_spi_setup_transfer(spi, t);
            if (status < 0)
                break;
            if (!t->speed_hz && !t->bits_per_word)
                par_override = 0;
        }

        if (!cs_active) {
            orion_spi_set_cs(orion_spi, 1);
            cs_active = 1;
        }

        if (t->len)
            m->actual_length += orion_spi_write_read(spi, t);

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

        if (t->cs_change) {
            orion_spi_set_cs(orion_spi, 0);
            cs_active = 0;
        }
    }

msg_done:
    if (cs_active)
        orion_spi_set_cs(orion_spi, 0);

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

    return 0;
}

static int __init orion_spi_reset(struct orion_spi *orion_spi)
{
    /* Verify that the CS is deasserted */
    orion_spi_set_cs(orion_spi, 0);

    return 0;
}

static int orion_spi_setup(struct spi_device *spi)
{
    struct orion_spi *orion_spi;

    orion_spi = spi_master_get_devdata(spi->master);

    if ((spi->max_speed_hz == 0)
            || (spi->max_speed_hz > orion_spi->max_speed))
        spi->max_speed_hz = orion_spi->max_speed;

    if (spi->max_speed_hz < orion_spi->min_speed) {
        dev_err(&spi->dev, "setup: requested speed too low %d Hz\n",
            spi->max_speed_hz);
        return -EINVAL;
    }

    /*
     * baudrate & width will be set orion_spi_setup_transfer
     */
    return 0;
}

static int __init orion_spi_probe(struct platform_device *pdev)
{
    struct spi_master *master;
    struct orion_spi *spi;
    struct resource *r;
    unsigned long tclk_hz;
    int status = 0;
    const u32 *iprop;
    int size;

    master = spi_alloc_master(&pdev->dev, sizeof *spi);
    if (master == NULL) {
        dev_dbg(&pdev->dev, "master allocation failed\n");
        return -ENOMEM;
    }

    if (pdev->id != -1)
        master->bus_num = pdev->id;
    if (pdev->dev.of_node) {
        iprop = of_get_property(pdev->dev.of_node, "cell-index",
                    &size);
        if (iprop && size == sizeof(*iprop))
            master->bus_num = *iprop;
    }

    /* we support only mode 0, and no options */
    master->mode_bits = 0;

    master->setup = orion_spi_setup;
    master->transfer_one_message = orion_spi_transfer_one_message;
    master->num_chipselect = ORION_NUM_CHIPSELECTS;

    dev_set_drvdata(&pdev->dev, master);

    spi = spi_master_get_devdata(master);
    spi->master = master;

    spi->clk = clk_get(&pdev->dev, NULL);
    if (IS_ERR(spi->clk)) {
        status = PTR_ERR(spi->clk);
        goto out;
    }

    clk_prepare(spi->clk);
    clk_enable(spi->clk);
    tclk_hz = clk_get_rate(spi->clk);
    spi->max_speed = DIV_ROUND_UP(tclk_hz, 4);
    spi->min_speed = DIV_ROUND_UP(tclk_hz, 30);

    r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (r == NULL) {
        status = -ENODEV;
        goto out_rel_clk;
    }

    if (!request_mem_region(r->start, resource_size(r),
                dev_name(&pdev->dev))) {
        status = -EBUSY;
        goto out_rel_clk;
    }
    spi->base = ioremap(r->start, SZ_1K);

    if (orion_spi_reset(spi) < 0)
        goto out_rel_mem;

    master->dev.of_node = pdev->dev.of_node;
    status = spi_register_master(master);
    if (status < 0)
        goto out_rel_mem;

    return status;

out_rel_mem:
    release_mem_region(r->start, resource_size(r));
out_rel_clk:
    clk_disable_unprepare(spi->clk);
    clk_put(spi->clk);
out:
    spi_master_put(master);
    return status;
}


static int __exit orion_spi_remove(struct platform_device *pdev)
{
    struct spi_master *master;
    struct resource *r;
    struct orion_spi *spi;

    master = dev_get_drvdata(&pdev->dev);
    spi = spi_master_get_devdata(master);

    clk_disable_unprepare(spi->clk);
    clk_put(spi->clk);

    r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    release_mem_region(r->start, resource_size(r));

    spi_unregister_master(master);

    return 0;
}

MODULE_ALIAS("platform:" DRIVER_NAME);

static const struct of_device_id orion_spi_of_match_table[] __devinitdata = {
    { .compatible = "marvell,orion-spi", },
    {}
};
MODULE_DEVICE_TABLE(of, orion_spi_of_match_table);

static struct platform_driver orion_spi_driver = {
    .driver = {
        .name   = DRIVER_NAME,
        .owner  = THIS_MODULE,
        .of_match_table = of_match_ptr(orion_spi_of_match_table),
    },
    .remove     = __exit_p(orion_spi_remove),
};

static int __init orion_spi_init(void)
{
    return platform_driver_probe(&orion_spi_driver, orion_spi_probe);
}
module_init(orion_spi_init);

static void __exit orion_spi_exit(void)
{
    platform_driver_unregister(&orion_spi_driver);
}
module_exit(orion_spi_exit);

MODULE_DESCRIPTION("Orion SPI driver");
MODULE_AUTHOR("Shadi Ammouri <[email protected]>");
MODULE_LICENSE("GPL");