ARM: 7409/1: Do not call flush_cache_user_range with mmap_sem held

[linux/fpc-iii.git] / drivers / net / caif / caif_spi.c

/*
 * Copyright (C) ST-Ericsson AB 2010
 * Contact: Sjur Brendeland / sjur.brandeland@stericsson.com
 * Author:  Daniel Martensson / Daniel.Martensson@stericsson.com
 * License terms: GNU General Public License (GPL) version 2.
 */

#include <linux/version.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/platform_device.h>
#include <linux/string.h>
#include <linux/workqueue.h>
#include <linux/completion.h>
#include <linux/list.h>
#include <linux/interrupt.h>
#include <linux/dma-mapping.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/debugfs.h>
#include <linux/if_arp.h>
#include <net/caif/caif_layer.h>
#include <net/caif/caif_spi.h>

#ifndef CONFIG_CAIF_SPI_SYNC
#define FLAVOR "Flavour: Vanilla.\n"
#else
#define FLAVOR "Flavour: Master CMD&LEN at start.\n"
#endif /* CONFIG_CAIF_SPI_SYNC */

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Daniel Martensson<daniel.martensson@stericsson.com>");
MODULE_DESCRIPTION("CAIF SPI driver");

/* Returns the number of padding bytes for alignment. */
#define PAD_POW2(x, pow) ((((x)&((pow)-1))==0) ? 0 : (((pow)-((x)&((pow)-1)))))

static int spi_loop;
module_param(spi_loop, bool, S_IRUGO);
MODULE_PARM_DESC(spi_loop, "SPI running in loopback mode.");

/* SPI frame alignment. */
module_param(spi_frm_align, int, S_IRUGO);
MODULE_PARM_DESC(spi_frm_align, "SPI frame alignment.");

/*
 * SPI padding options.
 * Warning: must be a base of 2 (& operation used) and can not be zero !
 */
module_param(spi_up_head_align, int, S_IRUGO);
MODULE_PARM_DESC(spi_up_head_align, "SPI uplink head alignment.");

module_param(spi_up_tail_align, int, S_IRUGO);
MODULE_PARM_DESC(spi_up_tail_align, "SPI uplink tail alignment.");

module_param(spi_down_head_align, int, S_IRUGO);
MODULE_PARM_DESC(spi_down_head_align, "SPI downlink head alignment.");

module_param(spi_down_tail_align, int, S_IRUGO);
MODULE_PARM_DESC(spi_down_tail_align, "SPI downlink tail alignment.");

#ifdef CONFIG_ARM
#define BYTE_HEX_FMT "%02X"
#else
#define BYTE_HEX_FMT "%02hhX"
#endif

#define SPI_MAX_PAYLOAD_SIZE 4096
/*
 * Threshold values for the SPI packet queue. Flowcontrol will be asserted
 * when the number of packets exceeds HIGH_WATER_MARK. It will not be
 * deasserted before the number of packets drops below LOW_WATER_MARK.
 */
#define LOW_WATER_MARK   100
#define HIGH_WATER_MARK  (LOW_WATER_MARK*5)

#ifdef CONFIG_UML

/*
 * We sometimes use UML for debugging, but it cannot handle
 * dma_alloc_coherent so we have to wrap it.
 */
static inline void *dma_alloc(dma_addr_t *daddr)
{
        return kmalloc(SPI_DMA_BUF_LEN, GFP_KERNEL);
}

static inline void dma_free(void *cpu_addr, dma_addr_t handle)
{
        kfree(cpu_addr);
}

#else

static inline void *dma_alloc(dma_addr_t *daddr)
{
        return dma_alloc_coherent(NULL, SPI_DMA_BUF_LEN, daddr,
                                GFP_KERNEL);
}

static inline void dma_free(void *cpu_addr, dma_addr_t handle)
{
        dma_free_coherent(NULL, SPI_DMA_BUF_LEN, cpu_addr, handle);
}
#endif  /* CONFIG_UML */

#ifdef CONFIG_DEBUG_FS

#define DEBUGFS_BUF_SIZE        4096

static struct dentry *dbgfs_root;

static inline void driver_debugfs_create(void)
{
        dbgfs_root = debugfs_create_dir(cfspi_spi_driver.driver.name, NULL);
}

static inline void driver_debugfs_remove(void)
{
        debugfs_remove(dbgfs_root);
}

static inline void dev_debugfs_rem(struct cfspi *cfspi)
{
        debugfs_remove(cfspi->dbgfs_frame);
        debugfs_remove(cfspi->dbgfs_state);
        debugfs_remove(cfspi->dbgfs_dir);
}

static int dbgfs_open(struct inode *inode, struct file *file)
{
        file->private_data = inode->i_private;
        return 0;
}

static ssize_t dbgfs_state(struct file *file, char __user *user_buf,
                           size_t count, loff_t *ppos)
{
        char *buf;
        int len = 0;
        ssize_t size;
        struct cfspi *cfspi = file->private_data;

        buf = kzalloc(DEBUGFS_BUF_SIZE, GFP_KERNEL);
        if (!buf)
                return 0;

        /* Print out debug information. */
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "CAIF SPI debug information:\n");

        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len), FLAVOR);

        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "STATE: %d\n", cfspi->dbg_state);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Previous CMD: 0x%x\n", cfspi->pcmd);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Current CMD: 0x%x\n", cfspi->cmd);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Previous TX len: %d\n", cfspi->tx_ppck_len);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Previous RX len: %d\n", cfspi->rx_ppck_len);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Current TX len: %d\n", cfspi->tx_cpck_len);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Current RX len: %d\n", cfspi->rx_cpck_len);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Next TX len: %d\n", cfspi->tx_npck_len);
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Next RX len: %d\n", cfspi->rx_npck_len);

        if (len > DEBUGFS_BUF_SIZE)
                len = DEBUGFS_BUF_SIZE;

        size = simple_read_from_buffer(user_buf, count, ppos, buf, len);
        kfree(buf);

        return size;
}

static ssize_t print_frame(char *buf, size_t size, char *frm,
                           size_t count, size_t cut)
{
        int len = 0;
        int i;
        for (i = 0; i < count; i++) {
                len += snprintf((buf + len), (size - len),
                                        "[0x" BYTE_HEX_FMT "]",
                                        frm[i]);
                if ((i == cut) && (count > (cut * 2))) {
                        /* Fast forward. */
                        i = count - cut;
                        len += snprintf((buf + len), (size - len),
                                        "--- %u bytes skipped ---\n",
                                        (int)(count - (cut * 2)));
                }

                if ((!(i % 10)) && i) {
                        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                                        "\n");
                }
        }
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len), "\n");
        return len;
}

static ssize_t dbgfs_frame(struct file *file, char __user *user_buf,
                           size_t count, loff_t *ppos)
{
        char *buf;
        int len = 0;
        ssize_t size;
        struct cfspi *cfspi;

        cfspi = file->private_data;
        buf = kzalloc(DEBUGFS_BUF_SIZE, GFP_KERNEL);
        if (!buf)
                return 0;

        /* Print out debug information. */
        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Current frame:\n");

        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Tx data (Len: %d):\n", cfspi->tx_cpck_len);

        len += print_frame((buf + len), (DEBUGFS_BUF_SIZE - len),
                           cfspi->xfer.va_tx,
                           (cfspi->tx_cpck_len + SPI_CMD_SZ), 100);

        len += snprintf((buf + len), (DEBUGFS_BUF_SIZE - len),
                        "Rx data (Len: %d):\n", cfspi->rx_cpck_len);

        len += print_frame((buf + len), (DEBUGFS_BUF_SIZE - len),
                           cfspi->xfer.va_rx,
                           (cfspi->rx_cpck_len + SPI_CMD_SZ), 100);

        size = simple_read_from_buffer(user_buf, count, ppos, buf, len);
        kfree(buf);

        return size;
}

static const struct file_operations dbgfs_state_fops = {
        .open = dbgfs_open,
        .read = dbgfs_state,
        .owner = THIS_MODULE
};

static const struct file_operations dbgfs_frame_fops = {
        .open = dbgfs_open,
        .read = dbgfs_frame,
        .owner = THIS_MODULE
};

static inline void dev_debugfs_add(struct cfspi *cfspi)
{
        cfspi->dbgfs_dir = debugfs_create_dir(cfspi->pdev->name, dbgfs_root);
        cfspi->dbgfs_state = debugfs_create_file("state", S_IRUGO,
                                                 cfspi->dbgfs_dir, cfspi,
                                                 &dbgfs_state_fops);
        cfspi->dbgfs_frame = debugfs_create_file("frame", S_IRUGO,
                                                 cfspi->dbgfs_dir, cfspi,
                                                 &dbgfs_frame_fops);
}

inline void cfspi_dbg_state(struct cfspi *cfspi, int state)
{
        cfspi->dbg_state = state;
};
#else

static inline void driver_debugfs_create(void)
{
}

static inline void driver_debugfs_remove(void)
{
}

static inline void dev_debugfs_add(struct cfspi *cfspi)
{
}

static inline void dev_debugfs_rem(struct cfspi *cfspi)
{
}

inline void cfspi_dbg_state(struct cfspi *cfspi, int state)
{
}
#endif                          /* CONFIG_DEBUG_FS */

static LIST_HEAD(cfspi_list);
static spinlock_t cfspi_list_lock;

/* SPI uplink head alignment. */
static ssize_t show_up_head_align(struct device_driver *driver, char *buf)
{
        return sprintf(buf, "%d\n", spi_up_head_align);
}

static DRIVER_ATTR(up_head_align, S_IRUSR, show_up_head_align, NULL);

/* SPI uplink tail alignment. */
static ssize_t show_up_tail_align(struct device_driver *driver, char *buf)
{
        return sprintf(buf, "%d\n", spi_up_tail_align);
}

static DRIVER_ATTR(up_tail_align, S_IRUSR, show_up_tail_align, NULL);

/* SPI downlink head alignment. */
static ssize_t show_down_head_align(struct device_driver *driver, char *buf)
{
        return sprintf(buf, "%d\n", spi_down_head_align);
}

static DRIVER_ATTR(down_head_align, S_IRUSR, show_down_head_align, NULL);

/* SPI downlink tail alignment. */
static ssize_t show_down_tail_align(struct device_driver *driver, char *buf)
{
        return sprintf(buf, "%d\n", spi_down_tail_align);
}

static DRIVER_ATTR(down_tail_align, S_IRUSR, show_down_tail_align, NULL);

/* SPI frame alignment. */
static ssize_t show_frame_align(struct device_driver *driver, char *buf)
{
        return sprintf(buf, "%d\n", spi_frm_align);
}

static DRIVER_ATTR(frame_align, S_IRUSR, show_frame_align, NULL);

int cfspi_xmitfrm(struct cfspi *cfspi, u8 *buf, size_t len)
{
        u8 *dst = buf;
        caif_assert(buf);

        if (cfspi->slave && !cfspi->slave_talked)
                cfspi->slave_talked = true;

        do {
                struct sk_buff *skb;
                struct caif_payload_info *info;
                int spad = 0;
                int epad;

                skb = skb_dequeue(&cfspi->chead);
                if (!skb)
                        break;

                /*
                 * Calculate length of frame including SPI padding.
                 * The payload position is found in the control buffer.
                 */
                info = (struct caif_payload_info *)&skb->cb;

                /*
                 * Compute head offset i.e. number of bytes to add to
                 * get the start of the payload aligned.
                 */
                if (spi_up_head_align > 1) {
                        spad = 1 + PAD_POW2((info->hdr_len + 1), spi_up_head_align);
                        *dst = (u8)(spad - 1);
                        dst += spad;
                }

                /* Copy in CAIF frame. */
                skb_copy_bits(skb, 0, dst, skb->len);
                dst += skb->len;
                cfspi->ndev->stats.tx_packets++;
                cfspi->ndev->stats.tx_bytes += skb->len;

                /*
                 * Compute tail offset i.e. number of bytes to add to
                 * get the complete CAIF frame aligned.
                 */
                epad = PAD_POW2((skb->len + spad), spi_up_tail_align);
                dst += epad;

                dev_kfree_skb(skb);

        } while ((dst - buf) < len);

        return dst - buf;
}

int cfspi_xmitlen(struct cfspi *cfspi)
{
        struct sk_buff *skb = NULL;
        int frm_len = 0;
        int pkts = 0;

        /*
         * Decommit previously committed frames.
         * skb_queue_splice_tail(&cfspi->chead,&cfspi->qhead)
         */
        while (skb_peek(&cfspi->chead)) {
                skb = skb_dequeue_tail(&cfspi->chead);
                skb_queue_head(&cfspi->qhead, skb);
        }

        do {
                struct caif_payload_info *info = NULL;
                int spad = 0;
                int epad = 0;

                skb = skb_dequeue(&cfspi->qhead);
                if (!skb)
                        break;

                /*
                 * Calculate length of frame including SPI padding.
                 * The payload position is found in the control buffer.
                 */
                info = (struct caif_payload_info *)&skb->cb;

                /*
                 * Compute head offset i.e. number of bytes to add to
                 * get the start of the payload aligned.
                 */
                if (spi_up_head_align > 1)
                        spad = 1 + PAD_POW2((info->hdr_len + 1), spi_up_head_align);

                /*
                 * Compute tail offset i.e. number of bytes to add to
                 * get the complete CAIF frame aligned.
                 */
                epad = PAD_POW2((skb->len + spad), spi_up_tail_align);

                if ((skb->len + spad + epad + frm_len) <= CAIF_MAX_SPI_FRAME) {
                        skb_queue_tail(&cfspi->chead, skb);
                        pkts++;
                        frm_len += skb->len + spad + epad;
                } else {
                        /* Put back packet. */
                        skb_queue_head(&cfspi->qhead, skb);
                        break;
                }
        } while (pkts <= CAIF_MAX_SPI_PKTS);

        /*
         * Send flow on if previously sent flow off
         * and now go below the low water mark
         */
        if (cfspi->flow_off_sent && cfspi->qhead.qlen < cfspi->qd_low_mark &&
                cfspi->cfdev.flowctrl) {
                cfspi->flow_off_sent = 0;
                cfspi->cfdev.flowctrl(cfspi->ndev, 1);
        }

        return frm_len;
}

static void cfspi_ss_cb(bool assert, struct cfspi_ifc *ifc)
{
        struct cfspi *cfspi = (struct cfspi *)ifc->priv;

        /*
         * The slave device is the master on the link. Interrupts before the
         * slave has transmitted are considered spurious.
         */
        if (cfspi->slave && !cfspi->slave_talked) {
                printk(KERN_WARNING "CFSPI: Spurious SS interrupt.\n");
                return;
        }

        if (!in_interrupt())
                spin_lock(&cfspi->lock);
        if (assert) {
                set_bit(SPI_SS_ON, &cfspi->state);
                set_bit(SPI_XFER, &cfspi->state);
        } else {
                set_bit(SPI_SS_OFF, &cfspi->state);
        }
        if (!in_interrupt())
                spin_unlock(&cfspi->lock);

        /* Wake up the xfer thread. */
        if (assert)
                wake_up_interruptible(&cfspi->wait);
}

static void cfspi_xfer_done_cb(struct cfspi_ifc *ifc)
{
        struct cfspi *cfspi = (struct cfspi *)ifc->priv;

        /* Transfer done, complete work queue */
        complete(&cfspi->comp);
}

static int cfspi_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct cfspi *cfspi = NULL;
        unsigned long flags;
        if (!dev)
                return -EINVAL;

        cfspi = netdev_priv(dev);

        skb_queue_tail(&cfspi->qhead, skb);

        spin_lock_irqsave(&cfspi->lock, flags);
        if (!test_and_set_bit(SPI_XFER, &cfspi->state)) {
                /* Wake up xfer thread. */
                wake_up_interruptible(&cfspi->wait);
        }
        spin_unlock_irqrestore(&cfspi->lock, flags);

        /* Send flow off if number of bytes is above high water mark */
        if (!cfspi->flow_off_sent &&
                cfspi->qhead.qlen > cfspi->qd_high_mark &&
                cfspi->cfdev.flowctrl) {
                cfspi->flow_off_sent = 1;
                cfspi->cfdev.flowctrl(cfspi->ndev, 0);
        }

        return 0;
}

int cfspi_rxfrm(struct cfspi *cfspi, u8 *buf, size_t len)
{
        u8 *src = buf;

        caif_assert(buf != NULL);

        do {
                int res;
                struct sk_buff *skb = NULL;
                int spad = 0;
                int epad = 0;
                u8 *dst = NULL;
                int pkt_len = 0;

                /*
                 * Compute head offset i.e. number of bytes added to
                 * get the start of the payload aligned.
                 */
                if (spi_down_head_align > 1) {
                        spad = 1 + *src;
                        src += spad;
                }

                /* Read length of CAIF frame (little endian). */
                pkt_len = *src;
                pkt_len |= ((*(src+1)) << 8) & 0xFF00;
                pkt_len += 2;   /* Add FCS fields. */

                /* Get a suitable caif packet and copy in data. */

                skb = netdev_alloc_skb(cfspi->ndev, pkt_len + 1);
                caif_assert(skb != NULL);

                dst = skb_put(skb, pkt_len);
                memcpy(dst, src, pkt_len);
                src += pkt_len;

                skb->protocol = htons(ETH_P_CAIF);
                skb_reset_mac_header(skb);
                skb->dev = cfspi->ndev;

                /*
                 * Push received packet up the stack.
                 */
                if (!spi_loop)
                        res = netif_rx_ni(skb);
                else
                        res = cfspi_xmit(skb, cfspi->ndev);

                if (!res) {
                        cfspi->ndev->stats.rx_packets++;
                        cfspi->ndev->stats.rx_bytes += pkt_len;
                } else
                        cfspi->ndev->stats.rx_dropped++;

                /*
                 * Compute tail offset i.e. number of bytes added to
                 * get the complete CAIF frame aligned.
                 */
                epad = PAD_POW2((pkt_len + spad), spi_down_tail_align);
                src += epad;
        } while ((src - buf) < len);

        return src - buf;
}

static int cfspi_open(struct net_device *dev)
{
        netif_wake_queue(dev);
        return 0;
}

static int cfspi_close(struct net_device *dev)
{
        netif_stop_queue(dev);
        return 0;
}
static const struct net_device_ops cfspi_ops = {
        .ndo_open = cfspi_open,
        .ndo_stop = cfspi_close,
        .ndo_start_xmit = cfspi_xmit
};

static void cfspi_setup(struct net_device *dev)
{
        struct cfspi *cfspi = netdev_priv(dev);
        dev->features = 0;
        dev->netdev_ops = &cfspi_ops;
        dev->type = ARPHRD_CAIF;
        dev->flags = IFF_NOARP | IFF_POINTOPOINT;
        dev->tx_queue_len = 0;
        dev->mtu = SPI_MAX_PAYLOAD_SIZE;
        dev->destructor = free_netdev;
        skb_queue_head_init(&cfspi->qhead);
        skb_queue_head_init(&cfspi->chead);
        cfspi->cfdev.link_select = CAIF_LINK_HIGH_BANDW;
        cfspi->cfdev.use_frag = false;
        cfspi->cfdev.use_stx = false;
        cfspi->cfdev.use_fcs = false;
        cfspi->ndev = dev;
}

int cfspi_spi_probe(struct platform_device *pdev)
{
        struct cfspi *cfspi = NULL;
        struct net_device *ndev;
        struct cfspi_dev *dev;
        int res;
        dev = (struct cfspi_dev *)pdev->dev.platform_data;

        ndev = alloc_netdev(sizeof(struct cfspi),
                        "cfspi%d", cfspi_setup);
        if (!ndev)
                return -ENOMEM;

        cfspi = netdev_priv(ndev);
        netif_stop_queue(ndev);
        cfspi->ndev = ndev;
        cfspi->pdev = pdev;

        /* Set flow info. */
        cfspi->flow_off_sent = 0;
        cfspi->qd_low_mark = LOW_WATER_MARK;
        cfspi->qd_high_mark = HIGH_WATER_MARK;

        /* Set slave info. */
        if (!strncmp(cfspi_spi_driver.driver.name, "cfspi_sspi", 10)) {
                cfspi->slave = true;
                cfspi->slave_talked = false;
        } else {
                cfspi->slave = false;
                cfspi->slave_talked = false;
        }

        /* Assign the SPI device. */
        cfspi->dev = dev;
        /* Assign the device ifc to this SPI interface. */
        dev->ifc = &cfspi->ifc;

        /* Allocate DMA buffers. */
        cfspi->xfer.va_tx = dma_alloc(&cfspi->xfer.pa_tx);
        if (!cfspi->xfer.va_tx) {
                printk(KERN_WARNING
                       "CFSPI: failed to allocate dma TX buffer.\n");
                res = -ENODEV;
                goto err_dma_alloc_tx;
        }

        cfspi->xfer.va_rx = dma_alloc(&cfspi->xfer.pa_rx);

        if (!cfspi->xfer.va_rx) {
                printk(KERN_WARNING
                       "CFSPI: failed to allocate dma TX buffer.\n");
                res = -ENODEV;
                goto err_dma_alloc_rx;
        }

        /* Initialize the work queue. */
        INIT_WORK(&cfspi->work, cfspi_xfer);

        /* Initialize spin locks. */
        spin_lock_init(&cfspi->lock);

        /* Initialize flow control state. */
        cfspi->flow_stop = false;

        /* Initialize wait queue. */
        init_waitqueue_head(&cfspi->wait);

        /* Create work thread. */
        cfspi->wq = create_singlethread_workqueue(dev->name);
        if (!cfspi->wq) {
                printk(KERN_WARNING "CFSPI: failed to create work queue.\n");
                res = -ENODEV;
                goto err_create_wq;
        }

        /* Initialize work queue. */
        init_completion(&cfspi->comp);

        /* Create debugfs entries. */
        dev_debugfs_add(cfspi);

        /* Set up the ifc. */
        cfspi->ifc.ss_cb = cfspi_ss_cb;
        cfspi->ifc.xfer_done_cb = cfspi_xfer_done_cb;
        cfspi->ifc.priv = cfspi;

        /* Add CAIF SPI device to list. */
        spin_lock(&cfspi_list_lock);
        list_add_tail(&cfspi->list, &cfspi_list);
        spin_unlock(&cfspi_list_lock);

        /* Schedule the work queue. */
        queue_work(cfspi->wq, &cfspi->work);

        /* Register network device. */
        res = register_netdev(ndev);
        if (res) {
                printk(KERN_ERR "CFSPI: Reg. error: %d.\n", res);
                goto err_net_reg;
        }
        return res;

 err_net_reg:
        dev_debugfs_rem(cfspi);
        set_bit(SPI_TERMINATE, &cfspi->state);
        wake_up_interruptible(&cfspi->wait);
        destroy_workqueue(cfspi->wq);
 err_create_wq:
        dma_free(cfspi->xfer.va_rx, cfspi->xfer.pa_rx);
 err_dma_alloc_rx:
        dma_free(cfspi->xfer.va_tx, cfspi->xfer.pa_tx);
 err_dma_alloc_tx:
        free_netdev(ndev);

        return res;
}

int cfspi_spi_remove(struct platform_device *pdev)
{
        struct list_head *list_node;
        struct list_head *n;
        struct cfspi *cfspi = NULL;
        struct cfspi_dev *dev;

        dev = (struct cfspi_dev *)pdev->dev.platform_data;
        spin_lock(&cfspi_list_lock);
        list_for_each_safe(list_node, n, &cfspi_list) {
                cfspi = list_entry(list_node, struct cfspi, list);
                /* Find the corresponding device. */
                if (cfspi->dev == dev) {
                        /* Remove from list. */
                        list_del(list_node);
                        /* Free DMA buffers. */
                        dma_free(cfspi->xfer.va_rx, cfspi->xfer.pa_rx);
                        dma_free(cfspi->xfer.va_tx, cfspi->xfer.pa_tx);
                        set_bit(SPI_TERMINATE, &cfspi->state);
                        wake_up_interruptible(&cfspi->wait);
                        destroy_workqueue(cfspi->wq);
                        /* Destroy debugfs directory and files. */
                        dev_debugfs_rem(cfspi);
                        unregister_netdev(cfspi->ndev);
                        spin_unlock(&cfspi_list_lock);
                        return 0;
                }
        }
        spin_unlock(&cfspi_list_lock);
        return -ENODEV;
}

static void __exit cfspi_exit_module(void)
{
        struct list_head *list_node;
        struct list_head *n;
        struct cfspi *cfspi = NULL;

        list_for_each_safe(list_node, n, &cfspi_list) {
                cfspi = list_entry(list_node, struct cfspi, list);
                platform_device_unregister(cfspi->pdev);
        }

        /* Destroy sysfs files. */
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_up_head_align);
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_up_tail_align);
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_down_head_align);
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_down_tail_align);
        driver_remove_file(&cfspi_spi_driver.driver, &driver_attr_frame_align);
        /* Unregister platform driver. */
        platform_driver_unregister(&cfspi_spi_driver);
        /* Destroy debugfs root directory. */
        driver_debugfs_remove();
}

static int __init cfspi_init_module(void)
{
        int result;

        /* Initialize spin lock. */
        spin_lock_init(&cfspi_list_lock);

        /* Register platform driver. */
        result = platform_driver_register(&cfspi_spi_driver);
        if (result) {
                printk(KERN_ERR "Could not register platform SPI driver.\n");
                goto err_dev_register;
        }

        /* Create sysfs files. */
        result =
            driver_create_file(&cfspi_spi_driver.driver,
                               &driver_attr_up_head_align);
        if (result) {
                printk(KERN_ERR "Sysfs creation failed 1.\n");
                goto err_create_up_head_align;
        }

        result =
            driver_create_file(&cfspi_spi_driver.driver,
                               &driver_attr_up_tail_align);
        if (result) {
                printk(KERN_ERR "Sysfs creation failed 2.\n");
                goto err_create_up_tail_align;
        }

        result =
            driver_create_file(&cfspi_spi_driver.driver,
                               &driver_attr_down_head_align);
        if (result) {
                printk(KERN_ERR "Sysfs creation failed 3.\n");
                goto err_create_down_head_align;
        }

        result =
            driver_create_file(&cfspi_spi_driver.driver,
                               &driver_attr_down_tail_align);
        if (result) {
                printk(KERN_ERR "Sysfs creation failed 4.\n");
                goto err_create_down_tail_align;
        }

        result =
            driver_create_file(&cfspi_spi_driver.driver,
                               &driver_attr_frame_align);
        if (result) {
                printk(KERN_ERR "Sysfs creation failed 5.\n");
                goto err_create_frame_align;
        }
        driver_debugfs_create();
        return result;

 err_create_frame_align:
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_down_tail_align);
 err_create_down_tail_align:
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_down_head_align);
 err_create_down_head_align:
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_up_tail_align);
 err_create_up_tail_align:
        driver_remove_file(&cfspi_spi_driver.driver,
                           &driver_attr_up_head_align);
 err_create_up_head_align:
 err_dev_register:
        return result;
}

module_init(cfspi_init_module);
module_exit(cfspi_exit_module);