root/drivers/net/ethernet/qualcomm/qca_spi.c
// SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
/*
 *   Copyright (c) 2011, 2012, Qualcomm Atheros Communications Inc.
 *   Copyright (c) 2014, I2SE GmbH
 */

/*   This module implements the Qualcomm Atheros SPI protocol for
 *   kernel-based SPI device; it is essentially an Ethernet-to-SPI
 *   serial converter;
 */

#include <linux/errno.h>
#include <linux/etherdevice.h>
#include <linux/if_arp.h>
#include <linux/if_ether.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/netdevice.h>
#include <linux/of.h>
#include <linux/of_net.h>
#include <linux/sched.h>
#include <linux/skbuff.h>
#include <linux/spi/spi.h>
#include <linux/types.h>

#include "qca_7k.h"
#include "qca_7k_common.h"
#include "qca_debug.h"
#include "qca_spi.h"

#define MAX_DMA_BURST_LEN 5000

#define SPI_INTR        0
#define SPI_RESET       1

/*   Modules parameters     */
#define QCASPI_CLK_SPEED_MIN 1000000
#define QCASPI_CLK_SPEED_MAX 16000000
#define QCASPI_CLK_SPEED     8000000
static int qcaspi_clkspeed;
module_param(qcaspi_clkspeed, int, 0);
MODULE_PARM_DESC(qcaspi_clkspeed, "SPI bus clock speed (Hz). Use 1000000-16000000.");

#define QCASPI_BURST_LEN_MIN 1
#define QCASPI_BURST_LEN_MAX MAX_DMA_BURST_LEN
static int qcaspi_burst_len = MAX_DMA_BURST_LEN;
module_param(qcaspi_burst_len, int, 0);
MODULE_PARM_DESC(qcaspi_burst_len, "Number of data bytes per burst. Use 1-5000.");

#define QCASPI_PLUGGABLE_MIN 0
#define QCASPI_PLUGGABLE_MAX 1
static int qcaspi_pluggable = QCASPI_PLUGGABLE_MAX;
module_param(qcaspi_pluggable, int, 0);
MODULE_PARM_DESC(qcaspi_pluggable, "Pluggable SPI connection (yes/no).");

#define QCASPI_WRITE_VERIFY_MIN 0
#define QCASPI_WRITE_VERIFY_MAX 3
static int wr_verify = QCASPI_WRITE_VERIFY_MIN;
module_param(wr_verify, int, 0);
MODULE_PARM_DESC(wr_verify, "SPI register write verify trails. Use 0-3.");

#define QCASPI_TX_TIMEOUT (1 * HZ)
#define QCASPI_QCA7K_REBOOT_TIME_MS 1000

static void
start_spi_intr_handling(struct qcaspi *qca, u16 *intr_cause)
{
        *intr_cause = 0;

        qcaspi_write_register(qca, SPI_REG_INTR_ENABLE, 0, wr_verify);
        qcaspi_read_register(qca, SPI_REG_INTR_CAUSE, intr_cause);
        netdev_dbg(qca->net_dev, "interrupts: 0x%04x\n", *intr_cause);
}

static void
end_spi_intr_handling(struct qcaspi *qca, u16 intr_cause)
{
        u16 intr_enable = (SPI_INT_CPU_ON |
                           SPI_INT_PKT_AVLBL |
                           SPI_INT_RDBUF_ERR |
                           SPI_INT_WRBUF_ERR);

        qcaspi_write_register(qca, SPI_REG_INTR_CAUSE, intr_cause, 0);
        qcaspi_write_register(qca, SPI_REG_INTR_ENABLE, intr_enable, wr_verify);
        netdev_dbg(qca->net_dev, "acking int: 0x%04x\n", intr_cause);
}

static u32
qcaspi_write_burst(struct qcaspi *qca, u8 *src, u32 len)
{
        __be16 cmd;
        struct spi_message msg;
        struct spi_transfer transfer[2];
        int ret;

        memset(&transfer, 0, sizeof(transfer));
        spi_message_init(&msg);

        cmd = cpu_to_be16(QCA7K_SPI_WRITE | QCA7K_SPI_EXTERNAL);
        transfer[0].tx_buf = &cmd;
        transfer[0].len = QCASPI_CMD_LEN;
        transfer[1].tx_buf = src;
        transfer[1].len = len;

        spi_message_add_tail(&transfer[0], &msg);
        spi_message_add_tail(&transfer[1], &msg);
        ret = spi_sync(qca->spi_dev, &msg);

        if (ret || (msg.actual_length != QCASPI_CMD_LEN + len)) {
                qcaspi_spi_error(qca);
                return 0;
        }

        return len;
}

static u32
qcaspi_write_legacy(struct qcaspi *qca, u8 *src, u32 len)
{
        struct spi_message msg;
        struct spi_transfer transfer;
        int ret;

        memset(&transfer, 0, sizeof(transfer));
        spi_message_init(&msg);

        transfer.tx_buf = src;
        transfer.len = len;

        spi_message_add_tail(&transfer, &msg);
        ret = spi_sync(qca->spi_dev, &msg);

        if (ret || (msg.actual_length != len)) {
                qcaspi_spi_error(qca);
                return 0;
        }

        return len;
}

static u32
qcaspi_read_burst(struct qcaspi *qca, u8 *dst, u32 len)
{
        struct spi_message msg;
        __be16 cmd;
        struct spi_transfer transfer[2];
        int ret;

        memset(&transfer, 0, sizeof(transfer));
        spi_message_init(&msg);

        cmd = cpu_to_be16(QCA7K_SPI_READ | QCA7K_SPI_EXTERNAL);
        transfer[0].tx_buf = &cmd;
        transfer[0].len = QCASPI_CMD_LEN;
        transfer[1].rx_buf = dst;
        transfer[1].len = len;

        spi_message_add_tail(&transfer[0], &msg);
        spi_message_add_tail(&transfer[1], &msg);
        ret = spi_sync(qca->spi_dev, &msg);

        if (ret || (msg.actual_length != QCASPI_CMD_LEN + len)) {
                qcaspi_spi_error(qca);
                return 0;
        }

        return len;
}

static u32
qcaspi_read_legacy(struct qcaspi *qca, u8 *dst, u32 len)
{
        struct spi_message msg;
        struct spi_transfer transfer;
        int ret;

        memset(&transfer, 0, sizeof(transfer));
        spi_message_init(&msg);

        transfer.rx_buf = dst;
        transfer.len = len;

        spi_message_add_tail(&transfer, &msg);
        ret = spi_sync(qca->spi_dev, &msg);

        if (ret || (msg.actual_length != len)) {
                qcaspi_spi_error(qca);
                return 0;
        }

        return len;
}

static int
qcaspi_tx_cmd(struct qcaspi *qca, u16 cmd)
{
        __be16 tx_data;
        struct spi_message msg;
        struct spi_transfer transfer;
        int ret;

        memset(&transfer, 0, sizeof(transfer));

        spi_message_init(&msg);

        tx_data = cpu_to_be16(cmd);
        transfer.len = sizeof(cmd);
        transfer.tx_buf = &tx_data;
        spi_message_add_tail(&transfer, &msg);

        ret = spi_sync(qca->spi_dev, &msg);

        if (!ret)
                ret = msg.status;

        if (ret)
                qcaspi_spi_error(qca);

        return ret;
}

static int
qcaspi_tx_frame(struct qcaspi *qca, struct sk_buff *skb)
{
        u32 count;
        u32 written;
        u32 offset;
        u32 len;

        len = skb->len;

        qcaspi_write_register(qca, SPI_REG_BFR_SIZE, len, wr_verify);
        if (qca->legacy_mode)
                qcaspi_tx_cmd(qca, QCA7K_SPI_WRITE | QCA7K_SPI_EXTERNAL);

        offset = 0;
        while (len) {
                count = len;
                if (count > qca->burst_len)
                        count = qca->burst_len;

                if (qca->legacy_mode) {
                        written = qcaspi_write_legacy(qca,
                                                      skb->data + offset,
                                                      count);
                } else {
                        written = qcaspi_write_burst(qca,
                                                     skb->data + offset,
                                                     count);
                }

                if (written != count)
                        return -1;

                offset += count;
                len -= count;
        }

        return 0;
}

static int
qcaspi_transmit(struct qcaspi *qca)
{
        struct net_device_stats *n_stats = &qca->net_dev->stats;
        u16 available = 0;
        u32 pkt_len;
        u16 new_head;
        u16 packets = 0;

        if (qca->txr.skb[qca->txr.head] == NULL)
                return 0;

        qcaspi_read_register(qca, SPI_REG_WRBUF_SPC_AVA, &available);

        if (available > QCASPI_HW_BUF_LEN) {
                /* This could only happen by interferences on the SPI line.
                 * So retry later ...
                 */
                qca->stats.buf_avail_err++;
                return -1;
        }

        while (qca->txr.skb[qca->txr.head]) {
                pkt_len = qca->txr.skb[qca->txr.head]->len + QCASPI_HW_PKT_LEN;

                if (available < pkt_len) {
                        if (packets == 0)
                                qca->stats.write_buf_miss++;
                        break;
                }

                if (qcaspi_tx_frame(qca, qca->txr.skb[qca->txr.head]) == -1) {
                        qca->stats.write_err++;
                        return -1;
                }

                packets++;
                n_stats->tx_packets++;
                n_stats->tx_bytes += qca->txr.skb[qca->txr.head]->len;
                available -= pkt_len;

                /* remove the skb from the queue */
                /* XXX After inconsistent lock states netif_tx_lock()
                 * has been replaced by netif_tx_lock_bh() and so on.
                 */
                netif_tx_lock_bh(qca->net_dev);
                dev_kfree_skb(qca->txr.skb[qca->txr.head]);
                qca->txr.skb[qca->txr.head] = NULL;
                qca->txr.size -= pkt_len;
                new_head = qca->txr.head + 1;
                if (new_head >= qca->txr.count)
                        new_head = 0;
                qca->txr.head = new_head;
                if (netif_queue_stopped(qca->net_dev))
                        netif_wake_queue(qca->net_dev);
                netif_tx_unlock_bh(qca->net_dev);
        }

        return 0;
}

static int
qcaspi_receive(struct qcaspi *qca)
{
        struct net_device *net_dev = qca->net_dev;
        struct net_device_stats *n_stats = &net_dev->stats;
        u16 available = 0;
        u32 bytes_read;
        u8 *cp;

        /* Allocate rx SKB if we don't have one available. */
        if (!qca->rx_skb) {
                qca->rx_skb = netdev_alloc_skb_ip_align(net_dev,
                                                        net_dev->mtu +
                                                        VLAN_ETH_HLEN);
                if (!qca->rx_skb) {
                        netdev_dbg(net_dev, "out of RX resources\n");
                        qca->stats.out_of_mem++;
                        return -1;
                }
        }

        /* Read the packet size. */
        qcaspi_read_register(qca, SPI_REG_RDBUF_BYTE_AVA, &available);

        netdev_dbg(net_dev, "qcaspi_receive: SPI_REG_RDBUF_BYTE_AVA: Value: %04x\n",
                   available);

        if (available > QCASPI_HW_BUF_LEN + QCASPI_HW_PKT_LEN) {
                /* This could only happen by interferences on the SPI line.
                 * So retry later ...
                 */
                qca->stats.buf_avail_err++;
                return -1;
        } else if (available == 0) {
                netdev_dbg(net_dev, "qcaspi_receive called without any data being available!\n");
                return -1;
        }

        qcaspi_write_register(qca, SPI_REG_BFR_SIZE, available, wr_verify);

        if (qca->legacy_mode)
                qcaspi_tx_cmd(qca, QCA7K_SPI_READ | QCA7K_SPI_EXTERNAL);

        while (available) {
                u32 count = available;

                if (count > qca->burst_len)
                        count = qca->burst_len;

                if (qca->legacy_mode) {
                        bytes_read = qcaspi_read_legacy(qca, qca->rx_buffer,
                                                        count);
                } else {
                        bytes_read = qcaspi_read_burst(qca, qca->rx_buffer,
                                                       count);
                }

                netdev_dbg(net_dev, "available: %d, byte read: %d\n",
                           available, bytes_read);

                if (bytes_read) {
                        available -= bytes_read;
                } else {
                        qca->stats.read_err++;
                        return -1;
                }

                cp = qca->rx_buffer;

                while ((bytes_read--) && (qca->rx_skb)) {
                        s32 retcode;

                        retcode = qcafrm_fsm_decode(&qca->frm_handle,
                                                    qca->rx_skb->data,
                                                    skb_tailroom(qca->rx_skb),
                                                    *cp);
                        cp++;
                        switch (retcode) {
                        case QCAFRM_GATHER:
                        case QCAFRM_NOHEAD:
                                break;
                        case QCAFRM_NOTAIL:
                                netdev_dbg(net_dev, "no RX tail\n");
                                n_stats->rx_errors++;
                                n_stats->rx_dropped++;
                                break;
                        case QCAFRM_INVLEN:
                                netdev_dbg(net_dev, "invalid RX length\n");
                                n_stats->rx_errors++;
                                n_stats->rx_dropped++;
                                break;
                        default:
                                qca->rx_skb->dev = qca->net_dev;
                                n_stats->rx_packets++;
                                n_stats->rx_bytes += retcode;
                                skb_put(qca->rx_skb, retcode);
                                qca->rx_skb->protocol = eth_type_trans(
                                        qca->rx_skb, qca->rx_skb->dev);
                                skb_checksum_none_assert(qca->rx_skb);
                                netif_rx(qca->rx_skb);
                                qca->rx_skb = netdev_alloc_skb_ip_align(net_dev,
                                        net_dev->mtu + VLAN_ETH_HLEN);
                                if (!qca->rx_skb) {
                                        netdev_dbg(net_dev, "out of RX resources\n");
                                        n_stats->rx_errors++;
                                        qca->stats.out_of_mem++;
                                        break;
                                }
                        }
                }
        }

        return 0;
}

/*   Check that tx ring stores only so much bytes
 *   that fit into the internal QCA buffer.
 */

static int
qcaspi_tx_ring_has_space(struct tx_ring *txr)
{
        if (txr->skb[txr->tail])
                return 0;

        return (txr->size + QCAFRM_MAX_LEN < QCASPI_HW_BUF_LEN) ? 1 : 0;
}

/*   Flush the tx ring. This function is only safe to
 *   call from the qcaspi_spi_thread.
 */

static void
qcaspi_flush_tx_ring(struct qcaspi *qca)
{
        int i;

        /* XXX After inconsistent lock states netif_tx_lock()
         * has been replaced by netif_tx_lock_bh() and so on.
         */
        netif_tx_lock_bh(qca->net_dev);
        for (i = 0; i < QCASPI_TX_RING_MAX_LEN; i++) {
                if (qca->txr.skb[i]) {
                        dev_kfree_skb(qca->txr.skb[i]);
                        qca->txr.skb[i] = NULL;
                        qca->net_dev->stats.tx_dropped++;
                }
        }
        qca->txr.tail = 0;
        qca->txr.head = 0;
        qca->txr.size = 0;
        netif_tx_unlock_bh(qca->net_dev);
}

static void
qcaspi_qca7k_sync(struct qcaspi *qca, int event)
{
        u16 signature = 0;
        u16 spi_config;
        u16 wrbuf_space = 0;

        if (event == QCASPI_EVENT_CPUON) {
                /* Read signature twice, if not valid
                 * go back to unknown state.
                 */
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
                if (signature != QCASPI_GOOD_SIGNATURE) {
                        if (qca->sync == QCASPI_SYNC_READY)
                                qca->stats.bad_signature++;

                        set_bit(SPI_RESET, &qca->flags);
                        netdev_dbg(qca->net_dev, "sync: got CPU on, but signature was invalid, restart\n");
                        return;
                } else {
                        /* ensure that the WRBUF is empty */
                        qcaspi_read_register(qca, SPI_REG_WRBUF_SPC_AVA,
                                             &wrbuf_space);
                        if (wrbuf_space != QCASPI_HW_BUF_LEN) {
                                netdev_dbg(qca->net_dev, "sync: got CPU on, but wrbuf not empty. reset!\n");
                                qca->sync = QCASPI_SYNC_UNKNOWN;
                                qca->stats.buf_avail_err++;
                        } else {
                                netdev_dbg(qca->net_dev, "sync: got CPU on, now in sync\n");
                                qca->sync = QCASPI_SYNC_READY;
                                return;
                        }
                }
        } else {
                /* Handle reset only on QCASPI_EVENT_UPDATE */
                if (test_and_clear_bit(SPI_RESET, &qca->flags))
                        qca->sync = QCASPI_SYNC_UNKNOWN;
        }

        switch (qca->sync) {
        case QCASPI_SYNC_READY:
                /* Check signature twice, if not valid go to unknown state. */
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
                if (signature != QCASPI_GOOD_SIGNATURE)
                        qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);

                if (signature != QCASPI_GOOD_SIGNATURE) {
                        set_bit(SPI_RESET, &qca->flags);
                        qca->stats.bad_signature++;
                        netdev_dbg(qca->net_dev, "sync: bad signature, restart\n");
                        /* don't reset right away */
                        return;
                }
                break;
        case QCASPI_SYNC_UNKNOWN:
                /* Read signature, if not valid stay in unknown state */
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
                if (signature != QCASPI_GOOD_SIGNATURE) {
                        netdev_dbg(qca->net_dev, "sync: could not read signature to reset device, retry.\n");
                        return;
                }

                /* TODO: use GPIO to reset QCA7000 in legacy mode*/
                netdev_dbg(qca->net_dev, "sync: resetting device.\n");
                qcaspi_read_register(qca, SPI_REG_SPI_CONFIG, &spi_config);
                spi_config |= QCASPI_SLAVE_RESET_BIT;
                qcaspi_write_register(qca, SPI_REG_SPI_CONFIG, spi_config, 0);

                qca->sync = QCASPI_SYNC_RESET;
                qca->stats.trig_reset++;
                qca->reset_count = 0;
                break;
        case QCASPI_SYNC_RESET:
                qca->reset_count++;
                netdev_dbg(qca->net_dev, "sync: waiting for CPU on, count %u.\n",
                           qca->reset_count);
                if (qca->reset_count >= QCASPI_RESET_TIMEOUT) {
                        /* reset did not seem to take place, try again */
                        set_bit(SPI_RESET, &qca->flags);
                        qca->stats.reset_timeout++;
                        netdev_dbg(qca->net_dev, "sync: reset timeout, restarting process.\n");
                }
                break;
        }
}

static int
qcaspi_spi_thread(void *data)
{
        struct qcaspi *qca = data;
        u16 intr_cause = 0;

        netdev_info(qca->net_dev, "SPI thread created\n");
        while (!kthread_should_stop()) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (kthread_should_park()) {
                        netif_tx_disable(qca->net_dev);
                        netif_carrier_off(qca->net_dev);
                        qcaspi_flush_tx_ring(qca);
                        kthread_parkme();
                        if (qca->sync == QCASPI_SYNC_READY) {
                                netif_carrier_on(qca->net_dev);
                                netif_wake_queue(qca->net_dev);
                        }
                        continue;
                }

                if (!qca->flags &&
                    !qca->txr.skb[qca->txr.head])
                        schedule();

                set_current_state(TASK_RUNNING);

                netdev_dbg(qca->net_dev, "have work to do. int: %lu, tx_skb: %p\n",
                           qca->flags,
                           qca->txr.skb[qca->txr.head]);

                qcaspi_qca7k_sync(qca, QCASPI_EVENT_UPDATE);

                if (qca->sync != QCASPI_SYNC_READY) {
                        netdev_dbg(qca->net_dev, "sync: not ready %u, turn off carrier and flush\n",
                                   (unsigned int)qca->sync);
                        netif_stop_queue(qca->net_dev);
                        netif_carrier_off(qca->net_dev);
                        qcaspi_flush_tx_ring(qca);
                        msleep(QCASPI_QCA7K_REBOOT_TIME_MS);
                }

                if (test_and_clear_bit(SPI_INTR, &qca->flags)) {
                        start_spi_intr_handling(qca, &intr_cause);

                        if (intr_cause & SPI_INT_CPU_ON) {
                                qcaspi_qca7k_sync(qca, QCASPI_EVENT_CPUON);

                                /* Frame decoding in progress */
                                if (qca->frm_handle.state != qca->frm_handle.init)
                                        qca->net_dev->stats.rx_dropped++;

                                qcafrm_fsm_init_spi(&qca->frm_handle);
                                qca->stats.device_reset++;

                                /* not synced. */
                                if (qca->sync != QCASPI_SYNC_READY)
                                        continue;

                                netif_wake_queue(qca->net_dev);
                                netif_carrier_on(qca->net_dev);
                        }

                        if (intr_cause & SPI_INT_RDBUF_ERR) {
                                /* restart sync */
                                netdev_dbg(qca->net_dev, "===> rdbuf error!\n");
                                qca->stats.read_buf_err++;
                                set_bit(SPI_RESET, &qca->flags);
                                continue;
                        }

                        if (intr_cause & SPI_INT_WRBUF_ERR) {
                                /* restart sync */
                                netdev_dbg(qca->net_dev, "===> wrbuf error!\n");
                                qca->stats.write_buf_err++;
                                set_bit(SPI_RESET, &qca->flags);
                                continue;
                        }

                        /* can only handle other interrupts
                         * if sync has occurred
                         */
                        if (qca->sync == QCASPI_SYNC_READY) {
                                if (intr_cause & SPI_INT_PKT_AVLBL)
                                        qcaspi_receive(qca);
                        }

                        end_spi_intr_handling(qca, intr_cause);
                }

                if (qca->sync == QCASPI_SYNC_READY)
                        qcaspi_transmit(qca);
        }
        set_current_state(TASK_RUNNING);
        netdev_info(qca->net_dev, "SPI thread exit\n");

        return 0;
}

static irqreturn_t
qcaspi_intr_handler(int irq, void *data)
{
        struct qcaspi *qca = data;

        set_bit(SPI_INTR, &qca->flags);
        if (qca->spi_thread)
                wake_up_process(qca->spi_thread);

        return IRQ_HANDLED;
}

static int
qcaspi_netdev_open(struct net_device *dev)
{
        struct qcaspi *qca = netdev_priv(dev);
        struct task_struct *thread;

        if (!qca)
                return -EINVAL;

        set_bit(SPI_INTR, &qca->flags);
        qca->sync = QCASPI_SYNC_UNKNOWN;
        qcafrm_fsm_init_spi(&qca->frm_handle);

        thread = kthread_run((void *)qcaspi_spi_thread,
                             qca, "%s", dev->name);

        if (IS_ERR(thread)) {
                netdev_err(dev, "%s: unable to start kernel thread.\n",
                           QCASPI_DRV_NAME);
                return PTR_ERR(thread);
        }

        qca->spi_thread = thread;

        enable_irq(qca->spi_dev->irq);

        /* SPI thread takes care of TX queue */

        return 0;
}

static int
qcaspi_netdev_close(struct net_device *dev)
{
        struct qcaspi *qca = netdev_priv(dev);

        netif_stop_queue(dev);

        qcaspi_write_register(qca, SPI_REG_INTR_ENABLE, 0, wr_verify);
        disable_irq(qca->spi_dev->irq);

        if (qca->spi_thread) {
                kthread_stop(qca->spi_thread);
                qca->spi_thread = NULL;
        }
        qcaspi_flush_tx_ring(qca);

        return 0;
}

static netdev_tx_t
qcaspi_netdev_xmit(struct sk_buff *skb, struct net_device *dev)
{
        u32 frame_len;
        u8 *ptmp;
        struct qcaspi *qca = netdev_priv(dev);
        u16 new_tail;
        struct sk_buff *tskb;
        u8 pad_len = 0;

        if (skb->len < QCAFRM_MIN_LEN)
                pad_len = QCAFRM_MIN_LEN - skb->len;

        if (qca->txr.skb[qca->txr.tail]) {
                netdev_warn(qca->net_dev, "queue was unexpectedly full!\n");
                netif_stop_queue(qca->net_dev);
                qca->stats.ring_full++;
                return NETDEV_TX_BUSY;
        }

        if ((skb_headroom(skb) < QCAFRM_HEADER_LEN) ||
            (skb_tailroom(skb) < QCAFRM_FOOTER_LEN + pad_len)) {
                tskb = skb_copy_expand(skb, QCAFRM_HEADER_LEN,
                                       QCAFRM_FOOTER_LEN + pad_len, GFP_ATOMIC);
                if (!tskb) {
                        qca->stats.out_of_mem++;
                        return NETDEV_TX_BUSY;
                }
                dev_kfree_skb(skb);
                skb = tskb;
        }

        frame_len = skb->len + pad_len;

        ptmp = skb_push(skb, QCAFRM_HEADER_LEN);
        qcafrm_create_header(ptmp, frame_len);

        if (pad_len) {
                ptmp = skb_put_zero(skb, pad_len);
        }

        ptmp = skb_put(skb, QCAFRM_FOOTER_LEN);
        qcafrm_create_footer(ptmp);

        netdev_dbg(qca->net_dev, "Tx-ing packet: Size: 0x%08x\n",
                   skb->len);

        qca->txr.size += skb->len + QCASPI_HW_PKT_LEN;

        new_tail = qca->txr.tail + 1;
        if (new_tail >= qca->txr.count)
                new_tail = 0;

        qca->txr.skb[qca->txr.tail] = skb;
        qca->txr.tail = new_tail;

        if (!qcaspi_tx_ring_has_space(&qca->txr)) {
                netif_stop_queue(qca->net_dev);
                qca->stats.ring_full++;
        }

        netif_trans_update(dev);

        if (qca->spi_thread)
                wake_up_process(qca->spi_thread);

        return NETDEV_TX_OK;
}

static void
qcaspi_netdev_tx_timeout(struct net_device *dev, unsigned int txqueue)
{
        struct qcaspi *qca = netdev_priv(dev);

        netdev_info(qca->net_dev, "Transmit timeout at %ld, latency %ld\n",
                    jiffies, jiffies - dev_trans_start(dev));
        qca->net_dev->stats.tx_errors++;
        /* Trigger tx queue flush and QCA7000 reset */
        set_bit(SPI_RESET, &qca->flags);

        if (qca->spi_thread)
                wake_up_process(qca->spi_thread);
}

static int
qcaspi_netdev_init(struct net_device *dev)
{
        struct qcaspi *qca = netdev_priv(dev);

        dev->mtu = QCAFRM_MAX_MTU;
        dev->type = ARPHRD_ETHER;
        qca->burst_len = qcaspi_burst_len;
        qca->spi_thread = NULL;
        qca->buffer_size = (QCAFRM_MAX_MTU + VLAN_ETH_HLEN + QCAFRM_HEADER_LEN +
                QCAFRM_FOOTER_LEN + QCASPI_HW_PKT_LEN) * QCASPI_RX_MAX_FRAMES;

        memset(&qca->stats, 0, sizeof(struct qcaspi_stats));

        qca->rx_buffer = kmalloc(qca->buffer_size, GFP_KERNEL);
        if (!qca->rx_buffer)
                return -ENOBUFS;

        qca->rx_skb = netdev_alloc_skb_ip_align(dev, qca->net_dev->mtu +
                                                VLAN_ETH_HLEN);
        if (!qca->rx_skb) {
                kfree(qca->rx_buffer);
                netdev_info(qca->net_dev, "Failed to allocate RX sk_buff.\n");
                return -ENOBUFS;
        }

        return 0;
}

static void
qcaspi_netdev_uninit(struct net_device *dev)
{
        struct qcaspi *qca = netdev_priv(dev);

        kfree(qca->rx_buffer);
        qca->buffer_size = 0;
        dev_kfree_skb(qca->rx_skb);
}

static const struct net_device_ops qcaspi_netdev_ops = {
        .ndo_init = qcaspi_netdev_init,
        .ndo_uninit = qcaspi_netdev_uninit,
        .ndo_open = qcaspi_netdev_open,
        .ndo_stop = qcaspi_netdev_close,
        .ndo_start_xmit = qcaspi_netdev_xmit,
        .ndo_set_mac_address = eth_mac_addr,
        .ndo_tx_timeout = qcaspi_netdev_tx_timeout,
        .ndo_validate_addr = eth_validate_addr,
};

static void
qcaspi_netdev_setup(struct net_device *dev)
{
        struct qcaspi *qca = NULL;

        dev->netdev_ops = &qcaspi_netdev_ops;
        qcaspi_set_ethtool_ops(dev);
        dev->watchdog_timeo = QCASPI_TX_TIMEOUT;
        dev->priv_flags &= ~IFF_TX_SKB_SHARING;
        dev->needed_tailroom = ALIGN(QCAFRM_FOOTER_LEN + QCAFRM_MIN_LEN, 4);
        dev->needed_headroom = ALIGN(QCAFRM_HEADER_LEN, 4);
        dev->tx_queue_len = 100;

        /* MTU range: 46 - 1500 */
        dev->min_mtu = QCAFRM_MIN_MTU;
        dev->max_mtu = QCAFRM_MAX_MTU;

        qca = netdev_priv(dev);
        memset(qca, 0, sizeof(struct qcaspi));

        memset(&qca->txr, 0, sizeof(qca->txr));
        qca->txr.count = QCASPI_TX_RING_MAX_LEN;
}

static const struct of_device_id qca_spi_of_match[] = {
        { .compatible = "qca,qca7000" },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(of, qca_spi_of_match);

static int
qca_spi_probe(struct spi_device *spi)
{
        struct qcaspi *qca = NULL;
        struct net_device *qcaspi_devs = NULL;
        u8 legacy_mode = 0;
        u16 signature;
        int ret;

        if (!spi->dev.of_node) {
                dev_err(&spi->dev, "Missing device tree\n");
                return -EINVAL;
        }

        legacy_mode = of_property_read_bool(spi->dev.of_node,
                                            "qca,legacy-mode");

        if (qcaspi_clkspeed)
                spi->max_speed_hz = qcaspi_clkspeed;
        else if (!spi->max_speed_hz)
                spi->max_speed_hz = QCASPI_CLK_SPEED;

        if (spi->max_speed_hz < QCASPI_CLK_SPEED_MIN ||
            spi->max_speed_hz > QCASPI_CLK_SPEED_MAX) {
                dev_err(&spi->dev, "Invalid clkspeed: %u\n",
                        spi->max_speed_hz);
                return -EINVAL;
        }

        if ((qcaspi_burst_len < QCASPI_BURST_LEN_MIN) ||
            (qcaspi_burst_len > QCASPI_BURST_LEN_MAX)) {
                dev_err(&spi->dev, "Invalid burst len: %d\n",
                        qcaspi_burst_len);
                return -EINVAL;
        }

        if ((qcaspi_pluggable < QCASPI_PLUGGABLE_MIN) ||
            (qcaspi_pluggable > QCASPI_PLUGGABLE_MAX)) {
                dev_err(&spi->dev, "Invalid pluggable: %d\n",
                        qcaspi_pluggable);
                return -EINVAL;
        }

        if (wr_verify < QCASPI_WRITE_VERIFY_MIN ||
            wr_verify > QCASPI_WRITE_VERIFY_MAX) {
                dev_err(&spi->dev, "Invalid write verify: %d\n",
                        wr_verify);
                return -EINVAL;
        }

        dev_info(&spi->dev, "ver=%s, clkspeed=%u, burst_len=%d, pluggable=%d\n",
                 QCASPI_DRV_VERSION,
                 spi->max_speed_hz,
                 qcaspi_burst_len,
                 qcaspi_pluggable);

        spi->mode = SPI_MODE_3;
        if (spi_setup(spi) < 0) {
                dev_err(&spi->dev, "Unable to setup SPI device\n");
                return -EFAULT;
        }

        qcaspi_devs = alloc_etherdev(sizeof(struct qcaspi));
        if (!qcaspi_devs)
                return -ENOMEM;

        qcaspi_netdev_setup(qcaspi_devs);
        SET_NETDEV_DEV(qcaspi_devs, &spi->dev);

        qca = netdev_priv(qcaspi_devs);
        if (!qca) {
                free_netdev(qcaspi_devs);
                dev_err(&spi->dev, "Fail to retrieve private structure\n");
                return -ENOMEM;
        }
        qca->net_dev = qcaspi_devs;
        qca->spi_dev = spi;
        qca->legacy_mode = legacy_mode;

        spi_set_drvdata(spi, qcaspi_devs);

        ret = devm_request_irq(&spi->dev, spi->irq, qcaspi_intr_handler,
                               IRQF_NO_AUTOEN, qca->net_dev->name, qca);
        if (ret) {
                dev_err(&spi->dev, "Unable to get IRQ %d (irqval=%d).\n",
                        spi->irq, ret);
                free_netdev(qcaspi_devs);
                return ret;
        }

        ret = of_get_ethdev_address(spi->dev.of_node, qca->net_dev);
        if (ret) {
                eth_hw_addr_random(qca->net_dev);
                dev_info(&spi->dev, "Using random MAC address: %pM\n",
                         qca->net_dev->dev_addr);
        }

        netif_carrier_off(qca->net_dev);

        if (!qcaspi_pluggable) {
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
                qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);

                if (signature != QCASPI_GOOD_SIGNATURE) {
                        dev_err(&spi->dev, "Invalid signature (expected 0x%04x, read 0x%04x)\n",
                                QCASPI_GOOD_SIGNATURE, signature);
                        free_netdev(qcaspi_devs);
                        return -EFAULT;
                }
        }

        if (register_netdev(qcaspi_devs)) {
                dev_err(&spi->dev, "Unable to register net device %s\n",
                        qcaspi_devs->name);
                free_netdev(qcaspi_devs);
                return -EFAULT;
        }

        qcaspi_init_device_debugfs(qca);

        return 0;
}

static void
qca_spi_remove(struct spi_device *spi)
{
        struct net_device *qcaspi_devs = spi_get_drvdata(spi);
        struct qcaspi *qca = netdev_priv(qcaspi_devs);

        qcaspi_remove_device_debugfs(qca);

        unregister_netdev(qcaspi_devs);
        free_netdev(qcaspi_devs);
}

static const struct spi_device_id qca_spi_id[] = {
        { "qca7000", 0 },
        { /* sentinel */ }
};
MODULE_DEVICE_TABLE(spi, qca_spi_id);

static struct spi_driver qca_spi_driver = {
        .driver = {
                .name   = QCASPI_DRV_NAME,
                .of_match_table = qca_spi_of_match,
        },
        .id_table = qca_spi_id,
        .probe    = qca_spi_probe,
        .remove   = qca_spi_remove,
};
module_spi_driver(qca_spi_driver);

MODULE_DESCRIPTION("Qualcomm Atheros QCA7000 SPI Driver");
MODULE_AUTHOR("Qualcomm Atheros Communications");
MODULE_AUTHOR("Stefan Wahren <wahrenst@gmx.net>");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION(QCASPI_DRV_VERSION);