spi-ti-ssp.c

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/*
 * Sequencer Serial Port (SSP) based SPI master driver
 *
 * Copyright (C) 2010 Texas Instruments Inc
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/kernel.h>
#include <linux/err.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/spi/spi.h>
#include <linux/mfd/ti_ssp.h>

#define MODE_BITS   (SPI_CPHA | SPI_CPOL | SPI_CS_HIGH)

struct ti_ssp_spi {
    struct spi_master       *master;
    struct device           *dev;
    spinlock_t          lock;
    struct list_head        msg_queue;
    struct completion       complete;
    bool                shutdown;
    struct workqueue_struct     *workqueue;
    struct work_struct      work;
    u8              mode, bpw;
    int             cs_active;
    u32             pc_en, pc_dis, pc_wr, pc_rd;
    void                (*select)(int cs);
};

static u32 ti_ssp_spi_rx(struct ti_ssp_spi *hw)
{
    u32 ret;

    ti_ssp_run(hw->dev, hw->pc_rd, 0, &ret);
    return ret;
}

static void ti_ssp_spi_tx(struct ti_ssp_spi *hw, u32 data)
{
    ti_ssp_run(hw->dev, hw->pc_wr, data << (32 - hw->bpw), NULL);
}

static int ti_ssp_spi_txrx(struct ti_ssp_spi *hw, struct spi_message *msg,
               struct spi_transfer *t)
{
    int count;

    if (hw->bpw <= 8) {
        u8      *rx = t->rx_buf;
        const u8    *tx = t->tx_buf;

        for (count = 0; count < t->len; count += 1) {
            if (t->tx_buf)
                ti_ssp_spi_tx(hw, *tx++);
            if (t->rx_buf)
                *rx++ = ti_ssp_spi_rx(hw);
        }
    } else if (hw->bpw <= 16) {
        u16     *rx = t->rx_buf;
        const u16   *tx = t->tx_buf;

        for (count = 0; count < t->len; count += 2) {
            if (t->tx_buf)
                ti_ssp_spi_tx(hw, *tx++);
            if (t->rx_buf)
                *rx++ = ti_ssp_spi_rx(hw);
        }
    } else {
        u32     *rx = t->rx_buf;
        const u32   *tx = t->tx_buf;

        for (count = 0; count < t->len; count += 4) {
            if (t->tx_buf)
                ti_ssp_spi_tx(hw, *tx++);
            if (t->rx_buf)
                *rx++ = ti_ssp_spi_rx(hw);
        }
    }

    msg->actual_length += count; /* bytes transferred */

    dev_dbg(&msg->spi->dev, "xfer %s%s, %d bytes, %d bpw, count %d%s\n",
        t->tx_buf ? "tx" : "", t->rx_buf ? "rx" : "", t->len,
        hw->bpw, count, (count < t->len) ? " (under)" : "");

    return (count < t->len) ? -EIO : 0; /* left over data */
}

static void ti_ssp_spi_chip_select(struct ti_ssp_spi *hw, int cs_active)
{
    cs_active = !!cs_active;
    if (cs_active == hw->cs_active)
        return;
    ti_ssp_run(hw->dev, cs_active ? hw->pc_en : hw->pc_dis, 0, NULL);
    hw->cs_active = cs_active;
}

#define __SHIFT_OUT(bits)   (SSP_OPCODE_SHIFT | SSP_OUT_MODE | \
                 cs_en | clk | SSP_COUNT((bits) * 2 - 1))
#define __SHIFT_IN(bits)    (SSP_OPCODE_SHIFT | SSP_IN_MODE  | \
                 cs_en | clk | SSP_COUNT((bits) * 2 - 1))

static int ti_ssp_spi_setup_transfer(struct ti_ssp_spi *hw, u8 bpw, u8 mode)
{
    int error, idx = 0;
    u32 seqram[16];
    u32 cs_en, cs_dis, clk;
    u32 topbits, botbits;

    mode &= MODE_BITS;
    if (mode == hw->mode && bpw == hw->bpw)
        return 0;

    cs_en  = (mode & SPI_CS_HIGH) ? SSP_CS_HIGH : SSP_CS_LOW;
    cs_dis = (mode & SPI_CS_HIGH) ? SSP_CS_LOW  : SSP_CS_HIGH;
    clk    = (mode & SPI_CPOL)    ? SSP_CLK_HIGH : SSP_CLK_LOW;

    /* Construct instructions */

    /* Disable Chip Select */
    hw->pc_dis = idx;
    seqram[idx++] = SSP_OPCODE_DIRECT | SSP_OUT_MODE | cs_dis | clk;
    seqram[idx++] = SSP_OPCODE_STOP   | SSP_OUT_MODE | cs_dis | clk;

    /* Enable Chip Select */
    hw->pc_en = idx;
    seqram[idx++] = SSP_OPCODE_DIRECT | SSP_OUT_MODE | cs_en | clk;
    seqram[idx++] = SSP_OPCODE_STOP   | SSP_OUT_MODE | cs_en | clk;

    /* Reads and writes need to be split for bpw > 16 */
    topbits = (bpw > 16) ? 16 : bpw;
    botbits = bpw - topbits;

    /* Write */
    hw->pc_wr = idx;
    seqram[idx++] = __SHIFT_OUT(topbits) | SSP_ADDR_REG;
    if (botbits)
        seqram[idx++] = __SHIFT_OUT(botbits)  | SSP_DATA_REG;
    seqram[idx++] = SSP_OPCODE_STOP | SSP_OUT_MODE | cs_en | clk;

    /* Read */
    hw->pc_rd = idx;
    if (botbits)
        seqram[idx++] = __SHIFT_IN(botbits) | SSP_ADDR_REG;
    seqram[idx++] = __SHIFT_IN(topbits) | SSP_DATA_REG;
    seqram[idx++] = SSP_OPCODE_STOP | SSP_OUT_MODE | cs_en | clk;

    error = ti_ssp_load(hw->dev, 0, seqram, idx);
    if (error < 0)
        return error;

    error = ti_ssp_set_mode(hw->dev, ((mode & SPI_CPHA) ?
                      0 : SSP_EARLY_DIN));
    if (error < 0)
        return error;

    hw->bpw = bpw;
    hw->mode = mode;

    return error;
}

static void ti_ssp_spi_work(struct work_struct *work)
{
    struct ti_ssp_spi *hw = container_of(work, struct ti_ssp_spi, work);

    spin_lock(&hw->lock);

     while (!list_empty(&hw->msg_queue)) {
        struct spi_message  *m;
        struct spi_device   *spi;
        struct spi_transfer *t = NULL;
        int         status = 0;

        m = container_of(hw->msg_queue.next, struct spi_message,
                 queue);

        list_del_init(&m->queue);

        spin_unlock(&hw->lock);

        spi = m->spi;

        if (hw->select)
            hw->select(spi->chip_select);

        list_for_each_entry(t, &m->transfers, transfer_list) {
            int bpw = spi->bits_per_word;
            int xfer_status;

            if (t->bits_per_word)
                bpw = t->bits_per_word;

            if (ti_ssp_spi_setup_transfer(hw, bpw, spi->mode) < 0)
                break;

            ti_ssp_spi_chip_select(hw, 1);

            xfer_status = ti_ssp_spi_txrx(hw, m, t);
            if (xfer_status < 0)
                status = xfer_status;

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

            if (t->cs_change)
                ti_ssp_spi_chip_select(hw, 0);
        }

        ti_ssp_spi_chip_select(hw, 0);
        m->status = status;
        m->complete(m->context);

        spin_lock(&hw->lock);
    }

    if (hw->shutdown)
        complete(&hw->complete);

    spin_unlock(&hw->lock);
}

static int ti_ssp_spi_setup(struct spi_device *spi)
{
    if (spi->bits_per_word > 32)
        return -EINVAL;

    return 0;
}

static int ti_ssp_spi_transfer(struct spi_device *spi, struct spi_message *m)
{
    struct ti_ssp_spi   *hw;
    struct spi_transfer *t;
    int         error = 0;

    m->actual_length = 0;
    m->status = -EINPROGRESS;

    hw = spi_master_get_devdata(spi->master);

    if (list_empty(&m->transfers) || !m->complete)
        return -EINVAL;

    list_for_each_entry(t, &m->transfers, transfer_list) {
        if (t->len && !(t->rx_buf || t->tx_buf)) {
            dev_err(&spi->dev, "invalid xfer, no buffer\n");
            return -EINVAL;
        }

        if (t->len && t->rx_buf && t->tx_buf) {
            dev_err(&spi->dev, "invalid xfer, full duplex\n");
            return -EINVAL;
        }

        if (t->bits_per_word > 32) {
            dev_err(&spi->dev, "invalid xfer width %d\n",
                t->bits_per_word);
            return -EINVAL;
        }
    }

    spin_lock(&hw->lock);
    if (hw->shutdown) {
        error = -ESHUTDOWN;
        goto error_unlock;
    }
    list_add_tail(&m->queue, &hw->msg_queue);
    queue_work(hw->workqueue, &hw->work);
error_unlock:
    spin_unlock(&hw->lock);
    return error;
}

static int __devinit ti_ssp_spi_probe(struct platform_device *pdev)
{
    const struct ti_ssp_spi_data *pdata;
    struct ti_ssp_spi *hw;
    struct spi_master *master;
    struct device *dev = &pdev->dev;
    int error = 0;

    pdata = dev->platform_data;
    if (!pdata) {
        dev_err(dev, "platform data not found\n");
        return -EINVAL;
    }

    master = spi_alloc_master(dev, sizeof(struct ti_ssp_spi));
    if (!master) {
        dev_err(dev, "cannot allocate SPI master\n");
        return -ENOMEM;
    }

    hw = spi_master_get_devdata(master);
    platform_set_drvdata(pdev, hw);

    hw->master = master;
    hw->dev = dev;
    hw->select = pdata->select;

    spin_lock_init(&hw->lock);
    init_completion(&hw->complete);
    INIT_LIST_HEAD(&hw->msg_queue);
    INIT_WORK(&hw->work, ti_ssp_spi_work);

    hw->workqueue = create_singlethread_workqueue(dev_name(dev));
    if (!hw->workqueue) {
        error = -ENOMEM;
        dev_err(dev, "work queue creation failed\n");
        goto error_wq;
    }

    error = ti_ssp_set_iosel(hw->dev, pdata->iosel);
    if (error < 0) {
        dev_err(dev, "io setup failed\n");
        goto error_iosel;
    }

    master->bus_num     = pdev->id;
    master->num_chipselect  = pdata->num_cs;
    master->mode_bits   = MODE_BITS;
    master->flags       = SPI_MASTER_HALF_DUPLEX;
    master->setup       = ti_ssp_spi_setup;
    master->transfer    = ti_ssp_spi_transfer;

    error = spi_register_master(master);
    if (error) {
        dev_err(dev, "master registration failed\n");
        goto error_reg;
    }

    return 0;

error_reg:
error_iosel:
    destroy_workqueue(hw->workqueue);
error_wq:
    spi_master_put(master);
    return error;
}

static int __devexit ti_ssp_spi_remove(struct platform_device *pdev)
{
    struct ti_ssp_spi *hw = platform_get_drvdata(pdev);
    int error;

    hw->shutdown = 1;
    while (!list_empty(&hw->msg_queue)) {
        error = wait_for_completion_interruptible(&hw->complete);
        if (error < 0) {
            hw->shutdown = 0;
            return error;
        }
    }
    destroy_workqueue(hw->workqueue);
    spi_unregister_master(hw->master);

    return 0;
}

static struct platform_driver ti_ssp_spi_driver = {
    .probe      = ti_ssp_spi_probe,
    .remove     = __devexit_p(ti_ssp_spi_remove),
    .driver     = {
        .name   = "ti-ssp-spi",
        .owner  = THIS_MODULE,
    },
};
module_platform_driver(ti_ssp_spi_driver);

MODULE_DESCRIPTION("SSP SPI Master");
MODULE_AUTHOR("Cyril Chemparathy");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ti-ssp-spi");