Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-bionic-kernel.git] / drivers / net / ethernet / sfc / tx.c

/****************************************************************************
 * Driver for Solarflare network controllers and boards
 * Copyright 2005-2006 Fen Systems Ltd.
 * Copyright 2005-2013 Solarflare Communications Inc.
 *
 * 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, incorporated herein by reference.
 */

#include <linux/pci.h>
#include <linux/tcp.h>
#include <linux/ip.h>
#include <linux/in.h>
#include <linux/ipv6.h>
#include <linux/slab.h>
#include <net/ipv6.h>
#include <linux/if_ether.h>
#include <linux/highmem.h>
#include <linux/cache.h>
#include "net_driver.h"
#include "efx.h"
#include "io.h"
#include "nic.h"
#include "tx.h"
#include "workarounds.h"
#include "ef10_regs.h"

#ifdef EFX_USE_PIO

#define EFX_PIOBUF_SIZE_DEF ALIGN(256, L1_CACHE_BYTES)
unsigned int efx_piobuf_size __read_mostly = EFX_PIOBUF_SIZE_DEF;

#endif /* EFX_USE_PIO */

static inline u8 *efx_tx_get_copy_buffer(struct efx_tx_queue *tx_queue,
                                         struct efx_tx_buffer *buffer)
{
        unsigned int index = efx_tx_queue_get_insert_index(tx_queue);
        struct efx_buffer *page_buf =
                &tx_queue->cb_page[index >> (PAGE_SHIFT - EFX_TX_CB_ORDER)];
        unsigned int offset =
                ((index << EFX_TX_CB_ORDER) + NET_IP_ALIGN) & (PAGE_SIZE - 1);

        if (unlikely(!page_buf->addr) &&
            efx_nic_alloc_buffer(tx_queue->efx, page_buf, PAGE_SIZE,
                                 GFP_ATOMIC))
                return NULL;
        buffer->dma_addr = page_buf->dma_addr + offset;
        buffer->unmap_len = 0;
        return (u8 *)page_buf->addr + offset;
}

u8 *efx_tx_get_copy_buffer_limited(struct efx_tx_queue *tx_queue,
                                   struct efx_tx_buffer *buffer, size_t len)
{
        if (len > EFX_TX_CB_SIZE)
                return NULL;
        return efx_tx_get_copy_buffer(tx_queue, buffer);
}

static void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
                               struct efx_tx_buffer *buffer,
                               unsigned int *pkts_compl,
                               unsigned int *bytes_compl)
{
        if (buffer->unmap_len) {
                struct device *dma_dev = &tx_queue->efx->pci_dev->dev;
                dma_addr_t unmap_addr = buffer->dma_addr - buffer->dma_offset;
                if (buffer->flags & EFX_TX_BUF_MAP_SINGLE)
                        dma_unmap_single(dma_dev, unmap_addr, buffer->unmap_len,
                                         DMA_TO_DEVICE);
                else
                        dma_unmap_page(dma_dev, unmap_addr, buffer->unmap_len,
                                       DMA_TO_DEVICE);
                buffer->unmap_len = 0;
        }

        if (buffer->flags & EFX_TX_BUF_SKB) {
                (*pkts_compl)++;
                (*bytes_compl) += buffer->skb->len;
                dev_consume_skb_any((struct sk_buff *)buffer->skb);
                netif_vdbg(tx_queue->efx, tx_done, tx_queue->efx->net_dev,
                           "TX queue %d transmission id %x complete\n",
                           tx_queue->queue, tx_queue->read_count);
        }

        buffer->len = 0;
        buffer->flags = 0;
}

unsigned int efx_tx_max_skb_descs(struct efx_nic *efx)
{
        /* Header and payload descriptor for each output segment, plus
         * one for every input fragment boundary within a segment
         */
        unsigned int max_descs = EFX_TSO_MAX_SEGS * 2 + MAX_SKB_FRAGS;

        /* Possibly one more per segment for option descriptors */
        if (efx_nic_rev(efx) >= EFX_REV_HUNT_A0)
                max_descs += EFX_TSO_MAX_SEGS;

        /* Possibly more for PCIe page boundaries within input fragments */
        if (PAGE_SIZE > EFX_PAGE_SIZE)
                max_descs += max_t(unsigned int, MAX_SKB_FRAGS,
                                   DIV_ROUND_UP(GSO_MAX_SIZE, EFX_PAGE_SIZE));

        return max_descs;
}

static void efx_tx_maybe_stop_queue(struct efx_tx_queue *txq1)
{
        /* We need to consider both queues that the net core sees as one */
        struct efx_tx_queue *txq2 = efx_tx_queue_partner(txq1);
        struct efx_nic *efx = txq1->efx;
        unsigned int fill_level;

        fill_level = max(txq1->insert_count - txq1->old_read_count,
                         txq2->insert_count - txq2->old_read_count);
        if (likely(fill_level < efx->txq_stop_thresh))
                return;

        /* We used the stale old_read_count above, which gives us a
         * pessimistic estimate of the fill level (which may even
         * validly be >= efx->txq_entries).  Now try again using
         * read_count (more likely to be a cache miss).
         *
         * If we read read_count and then conditionally stop the
         * queue, it is possible for the completion path to race with
         * us and complete all outstanding descriptors in the middle,
         * after which there will be no more completions to wake it.
         * Therefore we stop the queue first, then read read_count
         * (with a memory barrier to ensure the ordering), then
         * restart the queue if the fill level turns out to be low
         * enough.
         */
        netif_tx_stop_queue(txq1->core_txq);
        smp_mb();
        txq1->old_read_count = ACCESS_ONCE(txq1->read_count);
        txq2->old_read_count = ACCESS_ONCE(txq2->read_count);

        fill_level = max(txq1->insert_count - txq1->old_read_count,
                         txq2->insert_count - txq2->old_read_count);
        EFX_WARN_ON_ONCE_PARANOID(fill_level >= efx->txq_entries);
        if (likely(fill_level < efx->txq_stop_thresh)) {
                smp_mb();
                if (likely(!efx->loopback_selftest))
                        netif_tx_start_queue(txq1->core_txq);
        }
}

static int efx_enqueue_skb_copy(struct efx_tx_queue *tx_queue,
                                struct sk_buff *skb)
{
        unsigned int copy_len = skb->len;
        struct efx_tx_buffer *buffer;
        u8 *copy_buffer;
        int rc;

        EFX_WARN_ON_ONCE_PARANOID(copy_len > EFX_TX_CB_SIZE);

        buffer = efx_tx_queue_get_insert_buffer(tx_queue);

        copy_buffer = efx_tx_get_copy_buffer(tx_queue, buffer);
        if (unlikely(!copy_buffer))
                return -ENOMEM;

        rc = skb_copy_bits(skb, 0, copy_buffer, copy_len);
        EFX_WARN_ON_PARANOID(rc);
        buffer->len = copy_len;

        buffer->skb = skb;
        buffer->flags = EFX_TX_BUF_SKB;

        ++tx_queue->insert_count;
        return rc;
}

#ifdef EFX_USE_PIO

struct efx_short_copy_buffer {
        int used;
        u8 buf[L1_CACHE_BYTES];
};

/* Copy to PIO, respecting that writes to PIO buffers must be dword aligned.
 * Advances piobuf pointer. Leaves additional data in the copy buffer.
 */
static void efx_memcpy_toio_aligned(struct efx_nic *efx, u8 __iomem **piobuf,
                                    u8 *data, int len,
                                    struct efx_short_copy_buffer *copy_buf)
{
        int block_len = len & ~(sizeof(copy_buf->buf) - 1);

        __iowrite64_copy(*piobuf, data, block_len >> 3);
        *piobuf += block_len;
        len -= block_len;

        if (len) {
                data += block_len;
                BUG_ON(copy_buf->used);
                BUG_ON(len > sizeof(copy_buf->buf));
                memcpy(copy_buf->buf, data, len);
                copy_buf->used = len;
        }
}

/* Copy to PIO, respecting dword alignment, popping data from copy buffer first.
 * Advances piobuf pointer. Leaves additional data in the copy buffer.
 */
static void efx_memcpy_toio_aligned_cb(struct efx_nic *efx, u8 __iomem **piobuf,
                                       u8 *data, int len,
                                       struct efx_short_copy_buffer *copy_buf)
{
        if (copy_buf->used) {
                /* if the copy buffer is partially full, fill it up and write */
                int copy_to_buf =
                        min_t(int, sizeof(copy_buf->buf) - copy_buf->used, len);

                memcpy(copy_buf->buf + copy_buf->used, data, copy_to_buf);
                copy_buf->used += copy_to_buf;

                /* if we didn't fill it up then we're done for now */
                if (copy_buf->used < sizeof(copy_buf->buf))
                        return;

                __iowrite64_copy(*piobuf, copy_buf->buf,
                                 sizeof(copy_buf->buf) >> 3);
                *piobuf += sizeof(copy_buf->buf);
                data += copy_to_buf;
                len -= copy_to_buf;
                copy_buf->used = 0;
        }

        efx_memcpy_toio_aligned(efx, piobuf, data, len, copy_buf);
}

static void efx_flush_copy_buffer(struct efx_nic *efx, u8 __iomem *piobuf,
                                  struct efx_short_copy_buffer *copy_buf)
{
        /* if there's anything in it, write the whole buffer, including junk */
        if (copy_buf->used)
                __iowrite64_copy(piobuf, copy_buf->buf,
                                 sizeof(copy_buf->buf) >> 3);
}

/* Traverse skb structure and copy fragments in to PIO buffer.
 * Advances piobuf pointer.
 */
static void efx_skb_copy_bits_to_pio(struct efx_nic *efx, struct sk_buff *skb,
                                     u8 __iomem **piobuf,
                                     struct efx_short_copy_buffer *copy_buf)
{
        int i;

        efx_memcpy_toio_aligned(efx, piobuf, skb->data, skb_headlen(skb),
                                copy_buf);

        for (i = 0; i < skb_shinfo(skb)->nr_frags; ++i) {
                skb_frag_t *f = &skb_shinfo(skb)->frags[i];
                u8 *vaddr;

                vaddr = kmap_atomic(skb_frag_page(f));

                efx_memcpy_toio_aligned_cb(efx, piobuf, vaddr + f->page_offset,
                                           skb_frag_size(f), copy_buf);
                kunmap_atomic(vaddr);
        }

        EFX_WARN_ON_ONCE_PARANOID(skb_shinfo(skb)->frag_list);
}

static int efx_enqueue_skb_pio(struct efx_tx_queue *tx_queue,
                               struct sk_buff *skb)
{
        struct efx_tx_buffer *buffer =
                efx_tx_queue_get_insert_buffer(tx_queue);
        u8 __iomem *piobuf = tx_queue->piobuf;

        /* Copy to PIO buffer. Ensure the writes are padded to the end
         * of a cache line, as this is required for write-combining to be
         * effective on at least x86.
         */

        if (skb_shinfo(skb)->nr_frags) {
                /* The size of the copy buffer will ensure all writes
                 * are the size of a cache line.
                 */
                struct efx_short_copy_buffer copy_buf;

                copy_buf.used = 0;

                efx_skb_copy_bits_to_pio(tx_queue->efx, skb,
                                         &piobuf, &copy_buf);
                efx_flush_copy_buffer(tx_queue->efx, piobuf, &copy_buf);
        } else {
                /* Pad the write to the size of a cache line.
                 * We can do this because we know the skb_shared_info struct is
                 * after the source, and the destination buffer is big enough.
                 */
                BUILD_BUG_ON(L1_CACHE_BYTES >
                             SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
                __iowrite64_copy(tx_queue->piobuf, skb->data,
                                 ALIGN(skb->len, L1_CACHE_BYTES) >> 3);
        }

        buffer->skb = skb;
        buffer->flags = EFX_TX_BUF_SKB | EFX_TX_BUF_OPTION;

        EFX_POPULATE_QWORD_5(buffer->option,
                             ESF_DZ_TX_DESC_IS_OPT, 1,
                             ESF_DZ_TX_OPTION_TYPE, ESE_DZ_TX_OPTION_DESC_PIO,
                             ESF_DZ_TX_PIO_CONT, 0,
                             ESF_DZ_TX_PIO_BYTE_CNT, skb->len,
                             ESF_DZ_TX_PIO_BUF_ADDR,
                             tx_queue->piobuf_offset);
        ++tx_queue->insert_count;
        return 0;
}
#endif /* EFX_USE_PIO */

static struct efx_tx_buffer *efx_tx_map_chunk(struct efx_tx_queue *tx_queue,
                                              dma_addr_t dma_addr,
                                              size_t len)
{
        const struct efx_nic_type *nic_type = tx_queue->efx->type;
        struct efx_tx_buffer *buffer;
        unsigned int dma_len;

        /* Map the fragment taking account of NIC-dependent DMA limits. */
        do {
                buffer = efx_tx_queue_get_insert_buffer(tx_queue);
                dma_len = nic_type->tx_limit_len(tx_queue, dma_addr, len);

                buffer->len = dma_len;
                buffer->dma_addr = dma_addr;
                buffer->flags = EFX_TX_BUF_CONT;
                len -= dma_len;
                dma_addr += dma_len;
                ++tx_queue->insert_count;
        } while (len);

        return buffer;
}

/* Map all data from an SKB for DMA and create descriptors on the queue.
 */
static int efx_tx_map_data(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
                           unsigned int segment_count)
{
        struct efx_nic *efx = tx_queue->efx;
        struct device *dma_dev = &efx->pci_dev->dev;
        unsigned int frag_index, nr_frags;
        dma_addr_t dma_addr, unmap_addr;
        unsigned short dma_flags;
        size_t len, unmap_len;

        nr_frags = skb_shinfo(skb)->nr_frags;
        frag_index = 0;

        /* Map header data. */
        len = skb_headlen(skb);
        dma_addr = dma_map_single(dma_dev, skb->data, len, DMA_TO_DEVICE);
        dma_flags = EFX_TX_BUF_MAP_SINGLE;
        unmap_len = len;
        unmap_addr = dma_addr;

        if (unlikely(dma_mapping_error(dma_dev, dma_addr)))
                return -EIO;

        if (segment_count) {
                /* For TSO we need to put the header in to a separate
                 * descriptor. Map this separately if necessary.
                 */
                size_t header_len = skb_transport_header(skb) - skb->data +
                                (tcp_hdr(skb)->doff << 2u);

                if (header_len != len) {
                        tx_queue->tso_long_headers++;
                        efx_tx_map_chunk(tx_queue, dma_addr, header_len);
                        len -= header_len;
                        dma_addr += header_len;
                }
        }

        /* Add descriptors for each fragment. */
        do {
                struct efx_tx_buffer *buffer;
                skb_frag_t *fragment;

                buffer = efx_tx_map_chunk(tx_queue, dma_addr, len);

                /* The final descriptor for a fragment is responsible for
                 * unmapping the whole fragment.
                 */
                buffer->flags = EFX_TX_BUF_CONT | dma_flags;
                buffer->unmap_len = unmap_len;
                buffer->dma_offset = buffer->dma_addr - unmap_addr;

                if (frag_index >= nr_frags) {
                        /* Store SKB details with the final buffer for
                         * the completion.
                         */
                        buffer->skb = skb;
                        buffer->flags = EFX_TX_BUF_SKB | dma_flags;
                        return 0;
                }

                /* Move on to the next fragment. */
                fragment = &skb_shinfo(skb)->frags[frag_index++];
                len = skb_frag_size(fragment);
                dma_addr = skb_frag_dma_map(dma_dev, fragment,
                                0, len, DMA_TO_DEVICE);
                dma_flags = 0;
                unmap_len = len;
                unmap_addr = dma_addr;

                if (unlikely(dma_mapping_error(dma_dev, dma_addr)))
                        return -EIO;
        } while (1);
}

/* Remove buffers put into a tx_queue.  None of the buffers must have
 * an skb attached.
 */
static void efx_enqueue_unwind(struct efx_tx_queue *tx_queue)
{
        struct efx_tx_buffer *buffer;

        /* Work backwards until we hit the original insert pointer value */
        while (tx_queue->insert_count != tx_queue->write_count) {
                --tx_queue->insert_count;
                buffer = __efx_tx_queue_get_insert_buffer(tx_queue);
                efx_dequeue_buffer(tx_queue, buffer, NULL, NULL);
        }
}

/*
 * Fallback to software TSO.
 *
 * This is used if we are unable to send a GSO packet through hardware TSO.
 * This should only ever happen due to per-queue restrictions - unsupported
 * packets should first be filtered by the feature flags.
 *
 * Returns 0 on success, error code otherwise.
 */
static int efx_tx_tso_fallback(struct efx_tx_queue *tx_queue,
                               struct sk_buff *skb)
{
        struct sk_buff *segments, *next;

        segments = skb_gso_segment(skb, 0);
        if (IS_ERR(segments))
                return PTR_ERR(segments);

        dev_kfree_skb_any(skb);
        skb = segments;

        while (skb) {
                next = skb->next;
                skb->next = NULL;

                if (next)
                        skb->xmit_more = true;
                efx_enqueue_skb(tx_queue, skb);
                skb = next;
        }

        return 0;
}

/*
 * Add a socket buffer to a TX queue
 *
 * This maps all fragments of a socket buffer for DMA and adds them to
 * the TX queue.  The queue's insert pointer will be incremented by
 * the number of fragments in the socket buffer.
 *
 * If any DMA mapping fails, any mapped fragments will be unmapped,
 * the queue's insert pointer will be restored to its original value.
 *
 * This function is split out from efx_hard_start_xmit to allow the
 * loopback test to direct packets via specific TX queues.
 *
 * Returns NETDEV_TX_OK.
 * You must hold netif_tx_lock() to call this function.
 */
netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
{
        bool data_mapped = false;
        unsigned int segments;
        unsigned int skb_len;
        int rc;

        skb_len = skb->len;
        segments = skb_is_gso(skb) ? skb_shinfo(skb)->gso_segs : 0;
        if (segments == 1)
                segments = 0; /* Don't use TSO for a single segment. */

        /* Handle TSO first - it's *possible* (although unlikely) that we might
         * be passed a packet to segment that's smaller than the copybreak/PIO
         * size limit.
         */
        if (segments) {
                EFX_WARN_ON_ONCE_PARANOID(!tx_queue->handle_tso);
                rc = tx_queue->handle_tso(tx_queue, skb, &data_mapped);
                if (rc == -EINVAL) {
                        rc = efx_tx_tso_fallback(tx_queue, skb);
                        tx_queue->tso_fallbacks++;
                        if (rc == 0)
                                return 0;
                }
                if (rc)
                        goto err;
#ifdef EFX_USE_PIO
        } else if (skb_len <= efx_piobuf_size && !skb->xmit_more &&
                   efx_nic_may_tx_pio(tx_queue)) {
                /* Use PIO for short packets with an empty queue. */
                if (efx_enqueue_skb_pio(tx_queue, skb))
                        goto err;
                tx_queue->pio_packets++;
                data_mapped = true;
#endif
        } else if (skb->data_len && skb_len <= EFX_TX_CB_SIZE) {
                /* Pad short packets or coalesce short fragmented packets. */
                if (efx_enqueue_skb_copy(tx_queue, skb))
                        goto err;
                tx_queue->cb_packets++;
                data_mapped = true;
        }

        /* Map for DMA and create descriptors if we haven't done so already. */
        if (!data_mapped && (efx_tx_map_data(tx_queue, skb, segments)))
                goto err;

        /* Update BQL */
        netdev_tx_sent_queue(tx_queue->core_txq, skb_len);

        /* Pass off to hardware */
        if (!skb->xmit_more || netif_xmit_stopped(tx_queue->core_txq)) {
                struct efx_tx_queue *txq2 = efx_tx_queue_partner(tx_queue);

                /* There could be packets left on the partner queue if those
                 * SKBs had skb->xmit_more set. If we do not push those they
                 * could be left for a long time and cause a netdev watchdog.
                 */
                if (txq2->xmit_more_available)
                        efx_nic_push_buffers(txq2);

                efx_nic_push_buffers(tx_queue);
        } else {
                tx_queue->xmit_more_available = skb->xmit_more;
        }

        if (segments) {
                tx_queue->tso_bursts++;
                tx_queue->tso_packets += segments;
                tx_queue->tx_packets  += segments;
        } else {
                tx_queue->tx_packets++;
        }

        efx_tx_maybe_stop_queue(tx_queue);

        return NETDEV_TX_OK;


err:
        efx_enqueue_unwind(tx_queue);
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
}

/* Remove packets from the TX queue
 *
 * This removes packets from the TX queue, up to and including the
 * specified index.
 */
static void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
                                unsigned int index,
                                unsigned int *pkts_compl,
                                unsigned int *bytes_compl)
{
        struct efx_nic *efx = tx_queue->efx;
        unsigned int stop_index, read_ptr;

        stop_index = (index + 1) & tx_queue->ptr_mask;
        read_ptr = tx_queue->read_count & tx_queue->ptr_mask;

        while (read_ptr != stop_index) {
                struct efx_tx_buffer *buffer = &tx_queue->buffer[read_ptr];

                if (!(buffer->flags & EFX_TX_BUF_OPTION) &&
                    unlikely(buffer->len == 0)) {
                        netif_err(efx, tx_err, efx->net_dev,
                                  "TX queue %d spurious TX completion id %x\n",
                                  tx_queue->queue, read_ptr);
                        efx_schedule_reset(efx, RESET_TYPE_TX_SKIP);
                        return;
                }

                efx_dequeue_buffer(tx_queue, buffer, pkts_compl, bytes_compl);

                ++tx_queue->read_count;
                read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
        }
}

/* Initiate a packet transmission.  We use one channel per CPU
 * (sharing when we have more CPUs than channels).  On Falcon, the TX
 * completion events will be directed back to the CPU that transmitted
 * the packet, which should be cache-efficient.
 *
 * Context: non-blocking.
 * Note that returning anything other than NETDEV_TX_OK will cause the
 * OS to free the skb.
 */
netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
                                struct net_device *net_dev)
{
        struct efx_nic *efx = netdev_priv(net_dev);
        struct efx_tx_queue *tx_queue;
        unsigned index, type;

        EFX_WARN_ON_PARANOID(!netif_device_present(net_dev));

        /* PTP "event" packet */
        if (unlikely(efx_xmit_with_hwtstamp(skb)) &&
            unlikely(efx_ptp_is_ptp_tx(efx, skb))) {
                return efx_ptp_tx(efx, skb);
        }

        index = skb_get_queue_mapping(skb);
        type = skb->ip_summed == CHECKSUM_PARTIAL ? EFX_TXQ_TYPE_OFFLOAD : 0;
        if (index >= efx->n_tx_channels) {
                index -= efx->n_tx_channels;
                type |= EFX_TXQ_TYPE_HIGHPRI;
        }
        tx_queue = efx_get_tx_queue(efx, index, type);

        return efx_enqueue_skb(tx_queue, skb);
}

void efx_init_tx_queue_core_txq(struct efx_tx_queue *tx_queue)
{
        struct efx_nic *efx = tx_queue->efx;

        /* Must be inverse of queue lookup in efx_hard_start_xmit() */
        tx_queue->core_txq =
                netdev_get_tx_queue(efx->net_dev,
                                    tx_queue->queue / EFX_TXQ_TYPES +
                                    ((tx_queue->queue & EFX_TXQ_TYPE_HIGHPRI) ?
                                     efx->n_tx_channels : 0));
}

int efx_setup_tc(struct net_device *net_dev, u32 handle, u32 chain_index,
                 __be16 proto, struct tc_to_netdev *ntc)
{
        struct efx_nic *efx = netdev_priv(net_dev);
        struct efx_channel *channel;
        struct efx_tx_queue *tx_queue;
        unsigned tc, num_tc;
        int rc;

        if (ntc->type != TC_SETUP_MQPRIO)
                return -EINVAL;

        num_tc = ntc->mqprio->num_tc;

        if (num_tc > EFX_MAX_TX_TC)
                return -EINVAL;

        ntc->mqprio->hw = TC_MQPRIO_HW_OFFLOAD_TCS;

        if (num_tc == net_dev->num_tc)
                return 0;

        for (tc = 0; tc < num_tc; tc++) {
                net_dev->tc_to_txq[tc].offset = tc * efx->n_tx_channels;
                net_dev->tc_to_txq[tc].count = efx->n_tx_channels;
        }

        if (num_tc > net_dev->num_tc) {
                /* Initialise high-priority queues as necessary */
                efx_for_each_channel(channel, efx) {
                        efx_for_each_possible_channel_tx_queue(tx_queue,
                                                               channel) {
                                if (!(tx_queue->queue & EFX_TXQ_TYPE_HIGHPRI))
                                        continue;
                                if (!tx_queue->buffer) {
                                        rc = efx_probe_tx_queue(tx_queue);
                                        if (rc)
                                                return rc;
                                }
                                if (!tx_queue->initialised)
                                        efx_init_tx_queue(tx_queue);
                                efx_init_tx_queue_core_txq(tx_queue);
                        }
                }
        } else {
                /* Reduce number of classes before number of queues */
                net_dev->num_tc = num_tc;
        }

        rc = netif_set_real_num_tx_queues(net_dev,
                                          max_t(int, num_tc, 1) *
                                          efx->n_tx_channels);
        if (rc)
                return rc;

        /* Do not destroy high-priority queues when they become
         * unused.  We would have to flush them first, and it is
         * fairly difficult to flush a subset of TX queues.  Leave
         * it to efx_fini_channels().
         */

        net_dev->num_tc = num_tc;
        return 0;
}

void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
{
        unsigned fill_level;
        struct efx_nic *efx = tx_queue->efx;
        struct efx_tx_queue *txq2;
        unsigned int pkts_compl = 0, bytes_compl = 0;

        EFX_WARN_ON_ONCE_PARANOID(index > tx_queue->ptr_mask);

        efx_dequeue_buffers(tx_queue, index, &pkts_compl, &bytes_compl);
        tx_queue->pkts_compl += pkts_compl;
        tx_queue->bytes_compl += bytes_compl;

        if (pkts_compl > 1)
                ++tx_queue->merge_events;

        /* See if we need to restart the netif queue.  This memory
         * barrier ensures that we write read_count (inside
         * efx_dequeue_buffers()) before reading the queue status.
         */
        smp_mb();
        if (unlikely(netif_tx_queue_stopped(tx_queue->core_txq)) &&
            likely(efx->port_enabled) &&
            likely(netif_device_present(efx->net_dev))) {
                txq2 = efx_tx_queue_partner(tx_queue);
                fill_level = max(tx_queue->insert_count - tx_queue->read_count,
                                 txq2->insert_count - txq2->read_count);
                if (fill_level <= efx->txq_wake_thresh)
                        netif_tx_wake_queue(tx_queue->core_txq);
        }

        /* Check whether the hardware queue is now empty */
        if ((int)(tx_queue->read_count - tx_queue->old_write_count) >= 0) {
                tx_queue->old_write_count = ACCESS_ONCE(tx_queue->write_count);
                if (tx_queue->read_count == tx_queue->old_write_count) {
                        smp_mb();
                        tx_queue->empty_read_count =
                                tx_queue->read_count | EFX_EMPTY_COUNT_VALID;
                }
        }
}

static unsigned int efx_tx_cb_page_count(struct efx_tx_queue *tx_queue)
{
        return DIV_ROUND_UP(tx_queue->ptr_mask + 1, PAGE_SIZE >> EFX_TX_CB_ORDER);
}

int efx_probe_tx_queue(struct efx_tx_queue *tx_queue)
{
        struct efx_nic *efx = tx_queue->efx;
        unsigned int entries;
        int rc;

        /* Create the smallest power-of-two aligned ring */
        entries = max(roundup_pow_of_two(efx->txq_entries), EFX_MIN_DMAQ_SIZE);
        EFX_WARN_ON_PARANOID(entries > EFX_MAX_DMAQ_SIZE);
        tx_queue->ptr_mask = entries - 1;

        netif_dbg(efx, probe, efx->net_dev,
                  "creating TX queue %d size %#x mask %#x\n",
                  tx_queue->queue, efx->txq_entries, tx_queue->ptr_mask);

        /* Allocate software ring */
        tx_queue->buffer = kcalloc(entries, sizeof(*tx_queue->buffer),
                                   GFP_KERNEL);
        if (!tx_queue->buffer)
                return -ENOMEM;

        tx_queue->cb_page = kcalloc(efx_tx_cb_page_count(tx_queue),
                                    sizeof(tx_queue->cb_page[0]), GFP_KERNEL);
        if (!tx_queue->cb_page) {
                rc = -ENOMEM;
                goto fail1;
        }

        /* Allocate hardware ring */
        rc = efx_nic_probe_tx(tx_queue);
        if (rc)
                goto fail2;

        return 0;

fail2:
        kfree(tx_queue->cb_page);
        tx_queue->cb_page = NULL;
fail1:
        kfree(tx_queue->buffer);
        tx_queue->buffer = NULL;
        return rc;
}

void efx_init_tx_queue(struct efx_tx_queue *tx_queue)
{
        struct efx_nic *efx = tx_queue->efx;

        netif_dbg(efx, drv, efx->net_dev,
                  "initialising TX queue %d\n", tx_queue->queue);

        tx_queue->insert_count = 0;
        tx_queue->write_count = 0;
        tx_queue->packet_write_count = 0;
        tx_queue->old_write_count = 0;
        tx_queue->read_count = 0;
        tx_queue->old_read_count = 0;
        tx_queue->empty_read_count = 0 | EFX_EMPTY_COUNT_VALID;
        tx_queue->xmit_more_available = false;

        /* Set up default function pointers. These may get replaced by
         * efx_nic_init_tx() based off NIC/queue capabilities.
         */
        tx_queue->handle_tso = efx_enqueue_skb_tso;

        /* Set up TX descriptor ring */
        efx_nic_init_tx(tx_queue);

        tx_queue->initialised = true;
}

void efx_fini_tx_queue(struct efx_tx_queue *tx_queue)
{
        struct efx_tx_buffer *buffer;

        netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
                  "shutting down TX queue %d\n", tx_queue->queue);

        if (!tx_queue->buffer)
                return;

        /* Free any buffers left in the ring */
        while (tx_queue->read_count != tx_queue->write_count) {
                unsigned int pkts_compl = 0, bytes_compl = 0;
                buffer = &tx_queue->buffer[tx_queue->read_count & tx_queue->ptr_mask];
                efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);

                ++tx_queue->read_count;
        }
        tx_queue->xmit_more_available = false;
        netdev_tx_reset_queue(tx_queue->core_txq);
}

void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
{
        int i;

        if (!tx_queue->buffer)
                return;

        netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
                  "destroying TX queue %d\n", tx_queue->queue);
        efx_nic_remove_tx(tx_queue);

        if (tx_queue->cb_page) {
                for (i = 0; i < efx_tx_cb_page_count(tx_queue); i++)
                        efx_nic_free_buffer(tx_queue->efx,
                                            &tx_queue->cb_page[i]);
                kfree(tx_queue->cb_page);
                tx_queue->cb_page = NULL;
        }

        kfree(tx_queue->buffer);
        tx_queue->buffer = NULL;
}