Merge 4.14.24 into android-4.14

[GitHub/LineageOS/android_kernel_motorola_exynos9610.git] / drivers / net / ethernet / intel / i40evf / i40e_txrx.c

/*******************************************************************************
 *
 * Intel Ethernet Controller XL710 Family Linux Virtual Function Driver
 * Copyright(c) 2013 - 2016 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * The full GNU General Public License is included in this distribution in
 * the file called "COPYING".
 *
 * Contact Information:
 * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
 * Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124-6497
 *
 ******************************************************************************/

#include <linux/prefetch.h>
#include <net/busy_poll.h>

#include "i40evf.h"
#include "i40e_trace.h"
#include "i40e_prototype.h"

static inline __le64 build_ctob(u32 td_cmd, u32 td_offset, unsigned int size,
                                u32 td_tag)
{
        return cpu_to_le64(I40E_TX_DESC_DTYPE_DATA |
                           ((u64)td_cmd  << I40E_TXD_QW1_CMD_SHIFT) |
                           ((u64)td_offset << I40E_TXD_QW1_OFFSET_SHIFT) |
                           ((u64)size  << I40E_TXD_QW1_TX_BUF_SZ_SHIFT) |
                           ((u64)td_tag  << I40E_TXD_QW1_L2TAG1_SHIFT));
}

#define I40E_TXD_CMD (I40E_TX_DESC_CMD_EOP | I40E_TX_DESC_CMD_RS)

/**
 * i40e_unmap_and_free_tx_resource - Release a Tx buffer
 * @ring:      the ring that owns the buffer
 * @tx_buffer: the buffer to free
 **/
static void i40e_unmap_and_free_tx_resource(struct i40e_ring *ring,
                                            struct i40e_tx_buffer *tx_buffer)
{
        if (tx_buffer->skb) {
                if (tx_buffer->tx_flags & I40E_TX_FLAGS_FD_SB)
                        kfree(tx_buffer->raw_buf);
                else
                        dev_kfree_skb_any(tx_buffer->skb);
                if (dma_unmap_len(tx_buffer, len))
                        dma_unmap_single(ring->dev,
                                         dma_unmap_addr(tx_buffer, dma),
                                         dma_unmap_len(tx_buffer, len),
                                         DMA_TO_DEVICE);
        } else if (dma_unmap_len(tx_buffer, len)) {
                dma_unmap_page(ring->dev,
                               dma_unmap_addr(tx_buffer, dma),
                               dma_unmap_len(tx_buffer, len),
                               DMA_TO_DEVICE);
        }

        tx_buffer->next_to_watch = NULL;
        tx_buffer->skb = NULL;
        dma_unmap_len_set(tx_buffer, len, 0);
        /* tx_buffer must be completely set up in the transmit path */
}

/**
 * i40evf_clean_tx_ring - Free any empty Tx buffers
 * @tx_ring: ring to be cleaned
 **/
void i40evf_clean_tx_ring(struct i40e_ring *tx_ring)
{
        unsigned long bi_size;
        u16 i;

        /* ring already cleared, nothing to do */
        if (!tx_ring->tx_bi)
                return;

        /* Free all the Tx ring sk_buffs */
        for (i = 0; i < tx_ring->count; i++)
                i40e_unmap_and_free_tx_resource(tx_ring, &tx_ring->tx_bi[i]);

        bi_size = sizeof(struct i40e_tx_buffer) * tx_ring->count;
        memset(tx_ring->tx_bi, 0, bi_size);

        /* Zero out the descriptor ring */
        memset(tx_ring->desc, 0, tx_ring->size);

        tx_ring->next_to_use = 0;
        tx_ring->next_to_clean = 0;

        if (!tx_ring->netdev)
                return;

        /* cleanup Tx queue statistics */
        netdev_tx_reset_queue(txring_txq(tx_ring));
}

/**
 * i40evf_free_tx_resources - Free Tx resources per queue
 * @tx_ring: Tx descriptor ring for a specific queue
 *
 * Free all transmit software resources
 **/
void i40evf_free_tx_resources(struct i40e_ring *tx_ring)
{
        i40evf_clean_tx_ring(tx_ring);
        kfree(tx_ring->tx_bi);
        tx_ring->tx_bi = NULL;

        if (tx_ring->desc) {
                dma_free_coherent(tx_ring->dev, tx_ring->size,
                                  tx_ring->desc, tx_ring->dma);
                tx_ring->desc = NULL;
        }
}

/**
 * i40evf_get_tx_pending - how many Tx descriptors not processed
 * @tx_ring: the ring of descriptors
 * @in_sw: is tx_pending being checked in SW or HW
 *
 * Since there is no access to the ring head register
 * in XL710, we need to use our local copies
 **/
u32 i40evf_get_tx_pending(struct i40e_ring *ring, bool in_sw)
{
        u32 head, tail;

        head = ring->next_to_clean;
        tail = readl(ring->tail);

        if (head != tail)
                return (head < tail) ?
                        tail - head : (tail + ring->count - head);

        return 0;
}

#define WB_STRIDE 4

/**
 * i40e_clean_tx_irq - Reclaim resources after transmit completes
 * @vsi: the VSI we care about
 * @tx_ring: Tx ring to clean
 * @napi_budget: Used to determine if we are in netpoll
 *
 * Returns true if there's any budget left (e.g. the clean is finished)
 **/
static bool i40e_clean_tx_irq(struct i40e_vsi *vsi,
                              struct i40e_ring *tx_ring, int napi_budget)
{
        u16 i = tx_ring->next_to_clean;
        struct i40e_tx_buffer *tx_buf;
        struct i40e_tx_desc *tx_desc;
        unsigned int total_bytes = 0, total_packets = 0;
        unsigned int budget = vsi->work_limit;

        tx_buf = &tx_ring->tx_bi[i];
        tx_desc = I40E_TX_DESC(tx_ring, i);
        i -= tx_ring->count;

        do {
                struct i40e_tx_desc *eop_desc = tx_buf->next_to_watch;

                /* if next_to_watch is not set then there is no work pending */
                if (!eop_desc)
                        break;

                /* prevent any other reads prior to eop_desc */
                smp_rmb();

                i40e_trace(clean_tx_irq, tx_ring, tx_desc, tx_buf);
                /* if the descriptor isn't done, no work yet to do */
                if (!(eop_desc->cmd_type_offset_bsz &
                      cpu_to_le64(I40E_TX_DESC_DTYPE_DESC_DONE)))
                        break;

                /* clear next_to_watch to prevent false hangs */
                tx_buf->next_to_watch = NULL;

                /* update the statistics for this packet */
                total_bytes += tx_buf->bytecount;
                total_packets += tx_buf->gso_segs;

                /* free the skb */
                napi_consume_skb(tx_buf->skb, napi_budget);

                /* unmap skb header data */
                dma_unmap_single(tx_ring->dev,
                                 dma_unmap_addr(tx_buf, dma),
                                 dma_unmap_len(tx_buf, len),
                                 DMA_TO_DEVICE);

                /* clear tx_buffer data */
                tx_buf->skb = NULL;
                dma_unmap_len_set(tx_buf, len, 0);

                /* unmap remaining buffers */
                while (tx_desc != eop_desc) {
                        i40e_trace(clean_tx_irq_unmap,
                                   tx_ring, tx_desc, tx_buf);

                        tx_buf++;
                        tx_desc++;
                        i++;
                        if (unlikely(!i)) {
                                i -= tx_ring->count;
                                tx_buf = tx_ring->tx_bi;
                                tx_desc = I40E_TX_DESC(tx_ring, 0);
                        }

                        /* unmap any remaining paged data */
                        if (dma_unmap_len(tx_buf, len)) {
                                dma_unmap_page(tx_ring->dev,
                                               dma_unmap_addr(tx_buf, dma),
                                               dma_unmap_len(tx_buf, len),
                                               DMA_TO_DEVICE);
                                dma_unmap_len_set(tx_buf, len, 0);
                        }
                }

                /* move us one more past the eop_desc for start of next pkt */
                tx_buf++;
                tx_desc++;
                i++;
                if (unlikely(!i)) {
                        i -= tx_ring->count;
                        tx_buf = tx_ring->tx_bi;
                        tx_desc = I40E_TX_DESC(tx_ring, 0);
                }

                prefetch(tx_desc);

                /* update budget accounting */
                budget--;
        } while (likely(budget));

        i += tx_ring->count;
        tx_ring->next_to_clean = i;
        u64_stats_update_begin(&tx_ring->syncp);
        tx_ring->stats.bytes += total_bytes;
        tx_ring->stats.packets += total_packets;
        u64_stats_update_end(&tx_ring->syncp);
        tx_ring->q_vector->tx.total_bytes += total_bytes;
        tx_ring->q_vector->tx.total_packets += total_packets;

        if (tx_ring->flags & I40E_TXR_FLAGS_WB_ON_ITR) {
                /* check to see if there are < 4 descriptors
                 * waiting to be written back, then kick the hardware to force
                 * them to be written back in case we stay in NAPI.
                 * In this mode on X722 we do not enable Interrupt.
                 */
                unsigned int j = i40evf_get_tx_pending(tx_ring, false);

                if (budget &&
                    ((j / WB_STRIDE) == 0) && (j > 0) &&
                    !test_bit(__I40E_VSI_DOWN, vsi->state) &&
                    (I40E_DESC_UNUSED(tx_ring) != tx_ring->count))
                        tx_ring->arm_wb = true;
        }

        /* notify netdev of completed buffers */
        netdev_tx_completed_queue(txring_txq(tx_ring),
                                  total_packets, total_bytes);

#define TX_WAKE_THRESHOLD ((s16)(DESC_NEEDED * 2))
        if (unlikely(total_packets && netif_carrier_ok(tx_ring->netdev) &&
                     (I40E_DESC_UNUSED(tx_ring) >= TX_WAKE_THRESHOLD))) {
                /* Make sure that anybody stopping the queue after this
                 * sees the new next_to_clean.
                 */
                smp_mb();
                if (__netif_subqueue_stopped(tx_ring->netdev,
                                             tx_ring->queue_index) &&
                   !test_bit(__I40E_VSI_DOWN, vsi->state)) {
                        netif_wake_subqueue(tx_ring->netdev,
                                            tx_ring->queue_index);
                        ++tx_ring->tx_stats.restart_queue;
                }
        }

        return !!budget;
}

/**
 * i40evf_enable_wb_on_itr - Arm hardware to do a wb, interrupts are not enabled
 * @vsi: the VSI we care about
 * @q_vector: the vector on which to enable writeback
 *
 **/
static void i40e_enable_wb_on_itr(struct i40e_vsi *vsi,
                                  struct i40e_q_vector *q_vector)
{
        u16 flags = q_vector->tx.ring[0].flags;
        u32 val;

        if (!(flags & I40E_TXR_FLAGS_WB_ON_ITR))
                return;

        if (q_vector->arm_wb_state)
                return;

        val = I40E_VFINT_DYN_CTLN1_WB_ON_ITR_MASK |
              I40E_VFINT_DYN_CTLN1_ITR_INDX_MASK; /* set noitr */

        wr32(&vsi->back->hw,
             I40E_VFINT_DYN_CTLN1(q_vector->v_idx +
                                  vsi->base_vector - 1), val);
        q_vector->arm_wb_state = true;
}

/**
 * i40evf_force_wb - Issue SW Interrupt so HW does a wb
 * @vsi: the VSI we care about
 * @q_vector: the vector  on which to force writeback
 *
 **/
void i40evf_force_wb(struct i40e_vsi *vsi, struct i40e_q_vector *q_vector)
{
        u32 val = I40E_VFINT_DYN_CTLN1_INTENA_MASK |
                  I40E_VFINT_DYN_CTLN1_ITR_INDX_MASK | /* set noitr */
                  I40E_VFINT_DYN_CTLN1_SWINT_TRIG_MASK |
                  I40E_VFINT_DYN_CTLN1_SW_ITR_INDX_ENA_MASK
                  /* allow 00 to be written to the index */;

        wr32(&vsi->back->hw,
             I40E_VFINT_DYN_CTLN1(q_vector->v_idx + vsi->base_vector - 1),
             val);
}

/**
 * i40e_set_new_dynamic_itr - Find new ITR level
 * @rc: structure containing ring performance data
 *
 * Returns true if ITR changed, false if not
 *
 * Stores a new ITR value based on packets and byte counts during
 * the last interrupt.  The advantage of per interrupt computation
 * is faster updates and more accurate ITR for the current traffic
 * pattern.  Constants in this function were computed based on
 * theoretical maximum wire speed and thresholds were set based on
 * testing data as well as attempting to minimize response time
 * while increasing bulk throughput.
 **/
static bool i40e_set_new_dynamic_itr(struct i40e_ring_container *rc)
{
        enum i40e_latency_range new_latency_range = rc->latency_range;
        u32 new_itr = rc->itr;
        int bytes_per_int;
        unsigned int usecs, estimated_usecs;

        if (rc->total_packets == 0 || !rc->itr)
                return false;

        usecs = (rc->itr << 1) * ITR_COUNTDOWN_START;
        bytes_per_int = rc->total_bytes / usecs;

        /* The calculations in this algorithm depend on interrupts actually
         * firing at the ITR rate. This may not happen if the packet rate is
         * really low, or if we've been napi polling. Check to make sure
         * that's not the case before we continue.
         */
        estimated_usecs = jiffies_to_usecs(jiffies - rc->last_itr_update);
        if (estimated_usecs > usecs) {
                new_latency_range = I40E_LOW_LATENCY;
                goto reset_latency;
        }

        /* simple throttlerate management
         *   0-10MB/s   lowest (50000 ints/s)
         *  10-20MB/s   low    (20000 ints/s)
         *  20-1249MB/s bulk   (18000 ints/s)
         *
         * The math works out because the divisor is in 10^(-6) which
         * turns the bytes/us input value into MB/s values, but
         * make sure to use usecs, as the register values written
         * are in 2 usec increments in the ITR registers, and make sure
         * to use the smoothed values that the countdown timer gives us.
         */
        switch (new_latency_range) {
        case I40E_LOWEST_LATENCY:
                if (bytes_per_int > 10)
                        new_latency_range = I40E_LOW_LATENCY;
                break;
        case I40E_LOW_LATENCY:
                if (bytes_per_int > 20)
                        new_latency_range = I40E_BULK_LATENCY;
                else if (bytes_per_int <= 10)
                        new_latency_range = I40E_LOWEST_LATENCY;
                break;
        case I40E_BULK_LATENCY:
        default:
                if (bytes_per_int <= 20)
                        new_latency_range = I40E_LOW_LATENCY;
                break;
        }

reset_latency:
        rc->latency_range = new_latency_range;

        switch (new_latency_range) {
        case I40E_LOWEST_LATENCY:
                new_itr = I40E_ITR_50K;
                break;
        case I40E_LOW_LATENCY:
                new_itr = I40E_ITR_20K;
                break;
        case I40E_BULK_LATENCY:
                new_itr = I40E_ITR_18K;
                break;
        default:
                break;
        }

        rc->total_bytes = 0;
        rc->total_packets = 0;
        rc->last_itr_update = jiffies;

        if (new_itr != rc->itr) {
                rc->itr = new_itr;
                return true;
        }
        return false;
}

/**
 * i40evf_setup_tx_descriptors - Allocate the Tx descriptors
 * @tx_ring: the tx ring to set up
 *
 * Return 0 on success, negative on error
 **/
int i40evf_setup_tx_descriptors(struct i40e_ring *tx_ring)
{
        struct device *dev = tx_ring->dev;
        int bi_size;

        if (!dev)
                return -ENOMEM;

        /* warn if we are about to overwrite the pointer */
        WARN_ON(tx_ring->tx_bi);
        bi_size = sizeof(struct i40e_tx_buffer) * tx_ring->count;
        tx_ring->tx_bi = kzalloc(bi_size, GFP_KERNEL);
        if (!tx_ring->tx_bi)
                goto err;

        /* round up to nearest 4K */
        tx_ring->size = tx_ring->count * sizeof(struct i40e_tx_desc);
        tx_ring->size = ALIGN(tx_ring->size, 4096);
        tx_ring->desc = dma_alloc_coherent(dev, tx_ring->size,
                                           &tx_ring->dma, GFP_KERNEL);
        if (!tx_ring->desc) {
                dev_info(dev, "Unable to allocate memory for the Tx descriptor ring, size=%d\n",
                         tx_ring->size);
                goto err;
        }

        tx_ring->next_to_use = 0;
        tx_ring->next_to_clean = 0;
        return 0;

err:
        kfree(tx_ring->tx_bi);
        tx_ring->tx_bi = NULL;
        return -ENOMEM;
}

/**
 * i40evf_clean_rx_ring - Free Rx buffers
 * @rx_ring: ring to be cleaned
 **/
void i40evf_clean_rx_ring(struct i40e_ring *rx_ring)
{
        unsigned long bi_size;
        u16 i;

        /* ring already cleared, nothing to do */
        if (!rx_ring->rx_bi)
                return;

        if (rx_ring->skb) {
                dev_kfree_skb(rx_ring->skb);
                rx_ring->skb = NULL;
        }

        /* Free all the Rx ring sk_buffs */
        for (i = 0; i < rx_ring->count; i++) {
                struct i40e_rx_buffer *rx_bi = &rx_ring->rx_bi[i];

                if (!rx_bi->page)
                        continue;

                /* Invalidate cache lines that may have been written to by
                 * device so that we avoid corrupting memory.
                 */
                dma_sync_single_range_for_cpu(rx_ring->dev,
                                              rx_bi->dma,
                                              rx_bi->page_offset,
                                              rx_ring->rx_buf_len,
                                              DMA_FROM_DEVICE);

                /* free resources associated with mapping */
                dma_unmap_page_attrs(rx_ring->dev, rx_bi->dma,
                                     i40e_rx_pg_size(rx_ring),
                                     DMA_FROM_DEVICE,
                                     I40E_RX_DMA_ATTR);

                __page_frag_cache_drain(rx_bi->page, rx_bi->pagecnt_bias);

                rx_bi->page = NULL;
                rx_bi->page_offset = 0;
        }

        bi_size = sizeof(struct i40e_rx_buffer) * rx_ring->count;
        memset(rx_ring->rx_bi, 0, bi_size);

        /* Zero out the descriptor ring */
        memset(rx_ring->desc, 0, rx_ring->size);

        rx_ring->next_to_alloc = 0;
        rx_ring->next_to_clean = 0;
        rx_ring->next_to_use = 0;
}

/**
 * i40evf_free_rx_resources - Free Rx resources
 * @rx_ring: ring to clean the resources from
 *
 * Free all receive software resources
 **/
void i40evf_free_rx_resources(struct i40e_ring *rx_ring)
{
        i40evf_clean_rx_ring(rx_ring);
        kfree(rx_ring->rx_bi);
        rx_ring->rx_bi = NULL;

        if (rx_ring->desc) {
                dma_free_coherent(rx_ring->dev, rx_ring->size,
                                  rx_ring->desc, rx_ring->dma);
                rx_ring->desc = NULL;
        }
}

/**
 * i40evf_setup_rx_descriptors - Allocate Rx descriptors
 * @rx_ring: Rx descriptor ring (for a specific queue) to setup
 *
 * Returns 0 on success, negative on failure
 **/
int i40evf_setup_rx_descriptors(struct i40e_ring *rx_ring)
{
        struct device *dev = rx_ring->dev;
        int bi_size;

        /* warn if we are about to overwrite the pointer */
        WARN_ON(rx_ring->rx_bi);
        bi_size = sizeof(struct i40e_rx_buffer) * rx_ring->count;
        rx_ring->rx_bi = kzalloc(bi_size, GFP_KERNEL);
        if (!rx_ring->rx_bi)
                goto err;

        u64_stats_init(&rx_ring->syncp);

        /* Round up to nearest 4K */
        rx_ring->size = rx_ring->count * sizeof(union i40e_32byte_rx_desc);
        rx_ring->size = ALIGN(rx_ring->size, 4096);
        rx_ring->desc = dma_alloc_coherent(dev, rx_ring->size,
                                           &rx_ring->dma, GFP_KERNEL);

        if (!rx_ring->desc) {
                dev_info(dev, "Unable to allocate memory for the Rx descriptor ring, size=%d\n",
                         rx_ring->size);
                goto err;
        }

        rx_ring->next_to_alloc = 0;
        rx_ring->next_to_clean = 0;
        rx_ring->next_to_use = 0;

        return 0;
err:
        kfree(rx_ring->rx_bi);
        rx_ring->rx_bi = NULL;
        return -ENOMEM;
}

/**
 * i40e_release_rx_desc - Store the new tail and head values
 * @rx_ring: ring to bump
 * @val: new head index
 **/
static inline void i40e_release_rx_desc(struct i40e_ring *rx_ring, u32 val)
{
        rx_ring->next_to_use = val;

        /* update next to alloc since we have filled the ring */
        rx_ring->next_to_alloc = val;

        /* Force memory writes to complete before letting h/w
         * know there are new descriptors to fetch.  (Only
         * applicable for weak-ordered memory model archs,
         * such as IA-64).
         */
        wmb();
        writel(val, rx_ring->tail);
}

/**
 * i40e_rx_offset - Return expected offset into page to access data
 * @rx_ring: Ring we are requesting offset of
 *
 * Returns the offset value for ring into the data buffer.
 */
static inline unsigned int i40e_rx_offset(struct i40e_ring *rx_ring)
{
        return ring_uses_build_skb(rx_ring) ? I40E_SKB_PAD : 0;
}

/**
 * i40e_alloc_mapped_page - recycle or make a new page
 * @rx_ring: ring to use
 * @bi: rx_buffer struct to modify
 *
 * Returns true if the page was successfully allocated or
 * reused.
 **/
static bool i40e_alloc_mapped_page(struct i40e_ring *rx_ring,
                                   struct i40e_rx_buffer *bi)
{
        struct page *page = bi->page;
        dma_addr_t dma;

        /* since we are recycling buffers we should seldom need to alloc */
        if (likely(page)) {
                rx_ring->rx_stats.page_reuse_count++;
                return true;
        }

        /* alloc new page for storage */
        page = dev_alloc_pages(i40e_rx_pg_order(rx_ring));
        if (unlikely(!page)) {
                rx_ring->rx_stats.alloc_page_failed++;
                return false;
        }

        /* map page for use */
        dma = dma_map_page_attrs(rx_ring->dev, page, 0,
                                 i40e_rx_pg_size(rx_ring),
                                 DMA_FROM_DEVICE,
                                 I40E_RX_DMA_ATTR);

        /* if mapping failed free memory back to system since
         * there isn't much point in holding memory we can't use
         */
        if (dma_mapping_error(rx_ring->dev, dma)) {
                __free_pages(page, i40e_rx_pg_order(rx_ring));
                rx_ring->rx_stats.alloc_page_failed++;
                return false;
        }

        bi->dma = dma;
        bi->page = page;
        bi->page_offset = i40e_rx_offset(rx_ring);

        /* initialize pagecnt_bias to 1 representing we fully own page */
        bi->pagecnt_bias = 1;

        return true;
}

/**
 * i40e_receive_skb - Send a completed packet up the stack
 * @rx_ring:  rx ring in play
 * @skb: packet to send up
 * @vlan_tag: vlan tag for packet
 **/
static void i40e_receive_skb(struct i40e_ring *rx_ring,
                             struct sk_buff *skb, u16 vlan_tag)
{
        struct i40e_q_vector *q_vector = rx_ring->q_vector;

        if ((rx_ring->netdev->features & NETIF_F_HW_VLAN_CTAG_RX) &&
            (vlan_tag & VLAN_VID_MASK))
                __vlan_hwaccel_put_tag(skb, htons(ETH_P_8021Q), vlan_tag);

        napi_gro_receive(&q_vector->napi, skb);
}

/**
 * i40evf_alloc_rx_buffers - Replace used receive buffers
 * @rx_ring: ring to place buffers on
 * @cleaned_count: number of buffers to replace
 *
 * Returns false if all allocations were successful, true if any fail
 **/
bool i40evf_alloc_rx_buffers(struct i40e_ring *rx_ring, u16 cleaned_count)
{
        u16 ntu = rx_ring->next_to_use;
        union i40e_rx_desc *rx_desc;
        struct i40e_rx_buffer *bi;

        /* do nothing if no valid netdev defined */
        if (!rx_ring->netdev || !cleaned_count)
                return false;

        rx_desc = I40E_RX_DESC(rx_ring, ntu);
        bi = &rx_ring->rx_bi[ntu];

        do {
                if (!i40e_alloc_mapped_page(rx_ring, bi))
                        goto no_buffers;

                /* sync the buffer for use by the device */
                dma_sync_single_range_for_device(rx_ring->dev, bi->dma,
                                                 bi->page_offset,
                                                 rx_ring->rx_buf_len,
                                                 DMA_FROM_DEVICE);

                /* Refresh the desc even if buffer_addrs didn't change
                 * because each write-back erases this info.
                 */
                rx_desc->read.pkt_addr = cpu_to_le64(bi->dma + bi->page_offset);

                rx_desc++;
                bi++;
                ntu++;
                if (unlikely(ntu == rx_ring->count)) {
                        rx_desc = I40E_RX_DESC(rx_ring, 0);
                        bi = rx_ring->rx_bi;
                        ntu = 0;
                }

                /* clear the status bits for the next_to_use descriptor */
                rx_desc->wb.qword1.status_error_len = 0;

                cleaned_count--;
        } while (cleaned_count);

        if (rx_ring->next_to_use != ntu)
                i40e_release_rx_desc(rx_ring, ntu);

        return false;

no_buffers:
        if (rx_ring->next_to_use != ntu)
                i40e_release_rx_desc(rx_ring, ntu);

        /* make sure to come back via polling to try again after
         * allocation failure
         */
        return true;
}

/**
 * i40e_rx_checksum - Indicate in skb if hw indicated a good cksum
 * @vsi: the VSI we care about
 * @skb: skb currently being received and modified
 * @rx_desc: the receive descriptor
 **/
static inline void i40e_rx_checksum(struct i40e_vsi *vsi,
                                    struct sk_buff *skb,
                                    union i40e_rx_desc *rx_desc)
{
        struct i40e_rx_ptype_decoded decoded;
        u32 rx_error, rx_status;
        bool ipv4, ipv6;
        u8 ptype;
        u64 qword;

        qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);
        ptype = (qword & I40E_RXD_QW1_PTYPE_MASK) >> I40E_RXD_QW1_PTYPE_SHIFT;
        rx_error = (qword & I40E_RXD_QW1_ERROR_MASK) >>
                   I40E_RXD_QW1_ERROR_SHIFT;
        rx_status = (qword & I40E_RXD_QW1_STATUS_MASK) >>
                    I40E_RXD_QW1_STATUS_SHIFT;
        decoded = decode_rx_desc_ptype(ptype);

        skb->ip_summed = CHECKSUM_NONE;

        skb_checksum_none_assert(skb);

        /* Rx csum enabled and ip headers found? */
        if (!(vsi->netdev->features & NETIF_F_RXCSUM))
                return;

        /* did the hardware decode the packet and checksum? */
        if (!(rx_status & BIT(I40E_RX_DESC_STATUS_L3L4P_SHIFT)))
                return;

        /* both known and outer_ip must be set for the below code to work */
        if (!(decoded.known && decoded.outer_ip))
                return;

        ipv4 = (decoded.outer_ip == I40E_RX_PTYPE_OUTER_IP) &&
               (decoded.outer_ip_ver == I40E_RX_PTYPE_OUTER_IPV4);
        ipv6 = (decoded.outer_ip == I40E_RX_PTYPE_OUTER_IP) &&
               (decoded.outer_ip_ver == I40E_RX_PTYPE_OUTER_IPV6);

        if (ipv4 &&
            (rx_error & (BIT(I40E_RX_DESC_ERROR_IPE_SHIFT) |
                         BIT(I40E_RX_DESC_ERROR_EIPE_SHIFT))))
                goto checksum_fail;

        /* likely incorrect csum if alternate IP extension headers found */
        if (ipv6 &&
            rx_status & BIT(I40E_RX_DESC_STATUS_IPV6EXADD_SHIFT))
                /* don't increment checksum err here, non-fatal err */
                return;

        /* there was some L4 error, count error and punt packet to the stack */
        if (rx_error & BIT(I40E_RX_DESC_ERROR_L4E_SHIFT))
                goto checksum_fail;

        /* handle packets that were not able to be checksummed due
         * to arrival speed, in this case the stack can compute
         * the csum.
         */
        if (rx_error & BIT(I40E_RX_DESC_ERROR_PPRS_SHIFT))
                return;

        /* Only report checksum unnecessary for TCP, UDP, or SCTP */
        switch (decoded.inner_prot) {
        case I40E_RX_PTYPE_INNER_PROT_TCP:
        case I40E_RX_PTYPE_INNER_PROT_UDP:
        case I40E_RX_PTYPE_INNER_PROT_SCTP:
                skb->ip_summed = CHECKSUM_UNNECESSARY;
                /* fall though */
        default:
                break;
        }

        return;

checksum_fail:
        vsi->back->hw_csum_rx_error++;
}

/**
 * i40e_ptype_to_htype - get a hash type
 * @ptype: the ptype value from the descriptor
 *
 * Returns a hash type to be used by skb_set_hash
 **/
static inline int i40e_ptype_to_htype(u8 ptype)
{
        struct i40e_rx_ptype_decoded decoded = decode_rx_desc_ptype(ptype);

        if (!decoded.known)
                return PKT_HASH_TYPE_NONE;

        if (decoded.outer_ip == I40E_RX_PTYPE_OUTER_IP &&
            decoded.payload_layer == I40E_RX_PTYPE_PAYLOAD_LAYER_PAY4)
                return PKT_HASH_TYPE_L4;
        else if (decoded.outer_ip == I40E_RX_PTYPE_OUTER_IP &&
                 decoded.payload_layer == I40E_RX_PTYPE_PAYLOAD_LAYER_PAY3)
                return PKT_HASH_TYPE_L3;
        else
                return PKT_HASH_TYPE_L2;
}

/**
 * i40e_rx_hash - set the hash value in the skb
 * @ring: descriptor ring
 * @rx_desc: specific descriptor
 **/
static inline void i40e_rx_hash(struct i40e_ring *ring,
                                union i40e_rx_desc *rx_desc,
                                struct sk_buff *skb,
                                u8 rx_ptype)
{
        u32 hash;
        const __le64 rss_mask =
                cpu_to_le64((u64)I40E_RX_DESC_FLTSTAT_RSS_HASH <<
                            I40E_RX_DESC_STATUS_FLTSTAT_SHIFT);

        if (ring->netdev->features & NETIF_F_RXHASH)
                return;

        if ((rx_desc->wb.qword1.status_error_len & rss_mask) == rss_mask) {
                hash = le32_to_cpu(rx_desc->wb.qword0.hi_dword.rss);
                skb_set_hash(skb, hash, i40e_ptype_to_htype(rx_ptype));
        }
}

/**
 * i40evf_process_skb_fields - Populate skb header fields from Rx descriptor
 * @rx_ring: rx descriptor ring packet is being transacted on
 * @rx_desc: pointer to the EOP Rx descriptor
 * @skb: pointer to current skb being populated
 * @rx_ptype: the packet type decoded by hardware
 *
 * This function checks the ring, descriptor, and packet information in
 * order to populate the hash, checksum, VLAN, protocol, and
 * other fields within the skb.
 **/
static inline
void i40evf_process_skb_fields(struct i40e_ring *rx_ring,
                               union i40e_rx_desc *rx_desc, struct sk_buff *skb,
                               u8 rx_ptype)
{
        i40e_rx_hash(rx_ring, rx_desc, skb, rx_ptype);

        i40e_rx_checksum(rx_ring->vsi, skb, rx_desc);

        skb_record_rx_queue(skb, rx_ring->queue_index);

        /* modifies the skb - consumes the enet header */
        skb->protocol = eth_type_trans(skb, rx_ring->netdev);
}

/**
 * i40e_cleanup_headers - Correct empty headers
 * @rx_ring: rx descriptor ring packet is being transacted on
 * @skb: pointer to current skb being fixed
 *
 * Also address the case where we are pulling data in on pages only
 * and as such no data is present in the skb header.
 *
 * In addition if skb is not at least 60 bytes we need to pad it so that
 * it is large enough to qualify as a valid Ethernet frame.
 *
 * Returns true if an error was encountered and skb was freed.
 **/
static bool i40e_cleanup_headers(struct i40e_ring *rx_ring, struct sk_buff *skb)
{
        /* if eth_skb_pad returns an error the skb was freed */
        if (eth_skb_pad(skb))
                return true;

        return false;
}

/**
 * i40e_reuse_rx_page - page flip buffer and store it back on the ring
 * @rx_ring: rx descriptor ring to store buffers on
 * @old_buff: donor buffer to have page reused
 *
 * Synchronizes page for reuse by the adapter
 **/
static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
                               struct i40e_rx_buffer *old_buff)
{
        struct i40e_rx_buffer *new_buff;
        u16 nta = rx_ring->next_to_alloc;

        new_buff = &rx_ring->rx_bi[nta];

        /* update, and store next to alloc */
        nta++;
        rx_ring->next_to_alloc = (nta < rx_ring->count) ? nta : 0;

        /* transfer page from old buffer to new buffer */
        new_buff->dma           = old_buff->dma;
        new_buff->page          = old_buff->page;
        new_buff->page_offset   = old_buff->page_offset;
        new_buff->pagecnt_bias  = old_buff->pagecnt_bias;
}

/**
 * i40e_page_is_reusable - check if any reuse is possible
 * @page: page struct to check
 *
 * A page is not reusable if it was allocated under low memory
 * conditions, or it's not in the same NUMA node as this CPU.
 */
static inline bool i40e_page_is_reusable(struct page *page)
{
        return (page_to_nid(page) == numa_mem_id()) &&
                !page_is_pfmemalloc(page);
}

/**
 * i40e_can_reuse_rx_page - Determine if this page can be reused by
 * the adapter for another receive
 *
 * @rx_buffer: buffer containing the page
 *
 * If page is reusable, rx_buffer->page_offset is adjusted to point to
 * an unused region in the page.
 *
 * For small pages, @truesize will be a constant value, half the size
 * of the memory at page.  We'll attempt to alternate between high and
 * low halves of the page, with one half ready for use by the hardware
 * and the other half being consumed by the stack.  We use the page
 * ref count to determine whether the stack has finished consuming the
 * portion of this page that was passed up with a previous packet.  If
 * the page ref count is >1, we'll assume the "other" half page is
 * still busy, and this page cannot be reused.
 *
 * For larger pages, @truesize will be the actual space used by the
 * received packet (adjusted upward to an even multiple of the cache
 * line size).  This will advance through the page by the amount
 * actually consumed by the received packets while there is still
 * space for a buffer.  Each region of larger pages will be used at
 * most once, after which the page will not be reused.
 *
 * In either case, if the page is reusable its refcount is increased.
 **/
static bool i40e_can_reuse_rx_page(struct i40e_rx_buffer *rx_buffer)
{
        unsigned int pagecnt_bias = rx_buffer->pagecnt_bias;
        struct page *page = rx_buffer->page;

        /* Is any reuse possible? */
        if (unlikely(!i40e_page_is_reusable(page)))
                return false;

#if (PAGE_SIZE < 8192)
        /* if we are only owner of page we can reuse it */
        if (unlikely((page_count(page) - pagecnt_bias) > 1))
                return false;
#else
#define I40E_LAST_OFFSET \
        (SKB_WITH_OVERHEAD(PAGE_SIZE) - I40E_RXBUFFER_2048)
        if (rx_buffer->page_offset > I40E_LAST_OFFSET)
                return false;
#endif

        /* If we have drained the page fragment pool we need to update
         * the pagecnt_bias and page count so that we fully restock the
         * number of references the driver holds.
         */
        if (unlikely(!pagecnt_bias)) {
                page_ref_add(page, USHRT_MAX);
                rx_buffer->pagecnt_bias = USHRT_MAX;
        }

        return true;
}

/**
 * i40e_add_rx_frag - Add contents of Rx buffer to sk_buff
 * @rx_ring: rx descriptor ring to transact packets on
 * @rx_buffer: buffer containing page to add
 * @skb: sk_buff to place the data into
 * @size: packet length from rx_desc
 *
 * This function will add the data contained in rx_buffer->page to the skb.
 * It will just attach the page as a frag to the skb.
 *
 * The function will then update the page offset.
 **/
static void i40e_add_rx_frag(struct i40e_ring *rx_ring,
                             struct i40e_rx_buffer *rx_buffer,
                             struct sk_buff *skb,
                             unsigned int size)
{
#if (PAGE_SIZE < 8192)
        unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
#else
        unsigned int truesize = SKB_DATA_ALIGN(size + i40e_rx_offset(rx_ring));
#endif

        skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags, rx_buffer->page,
                        rx_buffer->page_offset, size, truesize);

        /* page is being used so we must update the page offset */
#if (PAGE_SIZE < 8192)
        rx_buffer->page_offset ^= truesize;
#else
        rx_buffer->page_offset += truesize;
#endif
}

/**
 * i40e_get_rx_buffer - Fetch Rx buffer and synchronize data for use
 * @rx_ring: rx descriptor ring to transact packets on
 * @size: size of buffer to add to skb
 *
 * This function will pull an Rx buffer from the ring and synchronize it
 * for use by the CPU.
 */
static struct i40e_rx_buffer *i40e_get_rx_buffer(struct i40e_ring *rx_ring,
                                                 const unsigned int size)
{
        struct i40e_rx_buffer *rx_buffer;

        rx_buffer = &rx_ring->rx_bi[rx_ring->next_to_clean];
        prefetchw(rx_buffer->page);

        /* we are reusing so sync this buffer for CPU use */
        dma_sync_single_range_for_cpu(rx_ring->dev,
                                      rx_buffer->dma,
                                      rx_buffer->page_offset,
                                      size,
                                      DMA_FROM_DEVICE);

        /* We have pulled a buffer for use, so decrement pagecnt_bias */
        rx_buffer->pagecnt_bias--;

        return rx_buffer;
}

/**
 * i40e_construct_skb - Allocate skb and populate it
 * @rx_ring: rx descriptor ring to transact packets on
 * @rx_buffer: rx buffer to pull data from
 * @size: size of buffer to add to skb
 *
 * This function allocates an skb.  It then populates it with the page
 * data from the current receive descriptor, taking care to set up the
 * skb correctly.
 */
static struct sk_buff *i40e_construct_skb(struct i40e_ring *rx_ring,
                                          struct i40e_rx_buffer *rx_buffer,
                                          unsigned int size)
{
        void *va = page_address(rx_buffer->page) + rx_buffer->page_offset;
#if (PAGE_SIZE < 8192)
        unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
#else
        unsigned int truesize = SKB_DATA_ALIGN(size);
#endif
        unsigned int headlen;
        struct sk_buff *skb;

        /* prefetch first cache line of first page */
        prefetch(va);
#if L1_CACHE_BYTES < 128
        prefetch(va + L1_CACHE_BYTES);
#endif

        /* allocate a skb to store the frags */
        skb = __napi_alloc_skb(&rx_ring->q_vector->napi,
                               I40E_RX_HDR_SIZE,
                               GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(!skb))
                return NULL;

        /* Determine available headroom for copy */
        headlen = size;
        if (headlen > I40E_RX_HDR_SIZE)
                headlen = eth_get_headlen(va, I40E_RX_HDR_SIZE);

        /* align pull length to size of long to optimize memcpy performance */
        memcpy(__skb_put(skb, headlen), va, ALIGN(headlen, sizeof(long)));

        /* update all of the pointers */
        size -= headlen;
        if (size) {
                skb_add_rx_frag(skb, 0, rx_buffer->page,
                                rx_buffer->page_offset + headlen,
                                size, truesize);

                /* buffer is used by skb, update page_offset */
#if (PAGE_SIZE < 8192)
                rx_buffer->page_offset ^= truesize;
#else
                rx_buffer->page_offset += truesize;
#endif
        } else {
                /* buffer is unused, reset bias back to rx_buffer */
                rx_buffer->pagecnt_bias++;
        }

        return skb;
}

/**
 * i40e_build_skb - Build skb around an existing buffer
 * @rx_ring: Rx descriptor ring to transact packets on
 * @rx_buffer: Rx buffer to pull data from
 * @size: size of buffer to add to skb
 *
 * This function builds an skb around an existing Rx buffer, taking care
 * to set up the skb correctly and avoid any memcpy overhead.
 */
static struct sk_buff *i40e_build_skb(struct i40e_ring *rx_ring,
                                      struct i40e_rx_buffer *rx_buffer,
                                      unsigned int size)
{
        void *va = page_address(rx_buffer->page) + rx_buffer->page_offset;
#if (PAGE_SIZE < 8192)
        unsigned int truesize = i40e_rx_pg_size(rx_ring) / 2;
#else
        unsigned int truesize = SKB_DATA_ALIGN(sizeof(struct skb_shared_info)) +
                                SKB_DATA_ALIGN(I40E_SKB_PAD + size);
#endif
        struct sk_buff *skb;

        /* prefetch first cache line of first page */
        prefetch(va);
#if L1_CACHE_BYTES < 128
        prefetch(va + L1_CACHE_BYTES);
#endif
        /* build an skb around the page buffer */
        skb = build_skb(va - I40E_SKB_PAD, truesize);
        if (unlikely(!skb))
                return NULL;

        /* update pointers within the skb to store the data */
        skb_reserve(skb, I40E_SKB_PAD);
        __skb_put(skb, size);

        /* buffer is used by skb, update page_offset */
#if (PAGE_SIZE < 8192)
        rx_buffer->page_offset ^= truesize;
#else
        rx_buffer->page_offset += truesize;
#endif

        return skb;
}

/**
 * i40e_put_rx_buffer - Clean up used buffer and either recycle or free
 * @rx_ring: rx descriptor ring to transact packets on
 * @rx_buffer: rx buffer to pull data from
 *
 * This function will clean up the contents of the rx_buffer.  It will
 * either recycle the bufer or unmap it and free the associated resources.
 */
static void i40e_put_rx_buffer(struct i40e_ring *rx_ring,
                               struct i40e_rx_buffer *rx_buffer)
{
        if (i40e_can_reuse_rx_page(rx_buffer)) {
                /* hand second half of page back to the ring */
                i40e_reuse_rx_page(rx_ring, rx_buffer);
                rx_ring->rx_stats.page_reuse_count++;
        } else {
                /* we are not reusing the buffer so unmap it */
                dma_unmap_page_attrs(rx_ring->dev, rx_buffer->dma,
                                     i40e_rx_pg_size(rx_ring),
                                     DMA_FROM_DEVICE, I40E_RX_DMA_ATTR);
                __page_frag_cache_drain(rx_buffer->page,
                                        rx_buffer->pagecnt_bias);
        }

        /* clear contents of buffer_info */
        rx_buffer->page = NULL;
}

/**
 * i40e_is_non_eop - process handling of non-EOP buffers
 * @rx_ring: Rx ring being processed
 * @rx_desc: Rx descriptor for current buffer
 * @skb: Current socket buffer containing buffer in progress
 *
 * This function updates next to clean.  If the buffer is an EOP buffer
 * this function exits returning false, otherwise it will place the
 * sk_buff in the next buffer to be chained and return true indicating
 * that this is in fact a non-EOP buffer.
 **/
static bool i40e_is_non_eop(struct i40e_ring *rx_ring,
                            union i40e_rx_desc *rx_desc,
                            struct sk_buff *skb)
{
        u32 ntc = rx_ring->next_to_clean + 1;

        /* fetch, update, and store next to clean */
        ntc = (ntc < rx_ring->count) ? ntc : 0;
        rx_ring->next_to_clean = ntc;

        prefetch(I40E_RX_DESC(rx_ring, ntc));

        /* if we are the last buffer then there is nothing else to do */
#define I40E_RXD_EOF BIT(I40E_RX_DESC_STATUS_EOF_SHIFT)
        if (likely(i40e_test_staterr(rx_desc, I40E_RXD_EOF)))
                return false;

        rx_ring->rx_stats.non_eop_descs++;

        return true;
}

/**
 * i40e_clean_rx_irq - Clean completed descriptors from Rx ring - bounce buf
 * @rx_ring: rx descriptor ring to transact packets on
 * @budget: Total limit on number of packets to process
 *
 * This function provides a "bounce buffer" approach to Rx interrupt
 * processing.  The advantage to this is that on systems that have
 * expensive overhead for IOMMU access this provides a means of avoiding
 * it by maintaining the mapping of the page to the system.
 *
 * Returns amount of work completed
 **/
static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget)
{
        unsigned int total_rx_bytes = 0, total_rx_packets = 0;
        struct sk_buff *skb = rx_ring->skb;
        u16 cleaned_count = I40E_DESC_UNUSED(rx_ring);
        bool failure = false;

        while (likely(total_rx_packets < (unsigned int)budget)) {
                struct i40e_rx_buffer *rx_buffer;
                union i40e_rx_desc *rx_desc;
                unsigned int size;
                u16 vlan_tag;
                u8 rx_ptype;
                u64 qword;

                /* return some buffers to hardware, one at a time is too slow */
                if (cleaned_count >= I40E_RX_BUFFER_WRITE) {
                        failure = failure ||
                                  i40evf_alloc_rx_buffers(rx_ring, cleaned_count);
                        cleaned_count = 0;
                }

                rx_desc = I40E_RX_DESC(rx_ring, rx_ring->next_to_clean);

                /* status_error_len will always be zero for unused descriptors
                 * because it's cleared in cleanup, and overlaps with hdr_addr
                 * which is always zero because packet split isn't used, if the
                 * hardware wrote DD then the length will be non-zero
                 */
                qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);

                /* This memory barrier is needed to keep us from reading
                 * any other fields out of the rx_desc until we have
                 * verified the descriptor has been written back.
                 */
                dma_rmb();

                size = (qword & I40E_RXD_QW1_LENGTH_PBUF_MASK) >>
                       I40E_RXD_QW1_LENGTH_PBUF_SHIFT;
                if (!size)
                        break;

                i40e_trace(clean_rx_irq, rx_ring, rx_desc, skb);
                rx_buffer = i40e_get_rx_buffer(rx_ring, size);

                /* retrieve a buffer from the ring */
                if (skb)
                        i40e_add_rx_frag(rx_ring, rx_buffer, skb, size);
                else if (ring_uses_build_skb(rx_ring))
                        skb = i40e_build_skb(rx_ring, rx_buffer, size);
                else
                        skb = i40e_construct_skb(rx_ring, rx_buffer, size);

                /* exit if we failed to retrieve a buffer */
                if (!skb) {
                        rx_ring->rx_stats.alloc_buff_failed++;
                        rx_buffer->pagecnt_bias++;
                        break;
                }

                i40e_put_rx_buffer(rx_ring, rx_buffer);
                cleaned_count++;

                if (i40e_is_non_eop(rx_ring, rx_desc, skb))
                        continue;

                /* ERR_MASK will only have valid bits if EOP set, and
                 * what we are doing here is actually checking
                 * I40E_RX_DESC_ERROR_RXE_SHIFT, since it is the zeroth bit in
                 * the error field
                 */
                if (unlikely(i40e_test_staterr(rx_desc, BIT(I40E_RXD_QW1_ERROR_SHIFT)))) {
                        dev_kfree_skb_any(skb);
                        skb = NULL;
                        continue;
                }

                if (i40e_cleanup_headers(rx_ring, skb)) {
                        skb = NULL;
                        continue;
                }

                /* probably a little skewed due to removing CRC */
                total_rx_bytes += skb->len;

                qword = le64_to_cpu(rx_desc->wb.qword1.status_error_len);
                rx_ptype = (qword & I40E_RXD_QW1_PTYPE_MASK) >>
                           I40E_RXD_QW1_PTYPE_SHIFT;

                /* populate checksum, VLAN, and protocol */
                i40evf_process_skb_fields(rx_ring, rx_desc, skb, rx_ptype);


                vlan_tag = (qword & BIT(I40E_RX_DESC_STATUS_L2TAG1P_SHIFT)) ?
                           le16_to_cpu(rx_desc->wb.qword0.lo_dword.l2tag1) : 0;

                i40e_trace(clean_rx_irq_rx, rx_ring, rx_desc, skb);
                i40e_receive_skb(rx_ring, skb, vlan_tag);
                skb = NULL;

                /* update budget accounting */
                total_rx_packets++;
        }

        rx_ring->skb = skb;

        u64_stats_update_begin(&rx_ring->syncp);
        rx_ring->stats.packets += total_rx_packets;
        rx_ring->stats.bytes += total_rx_bytes;
        u64_stats_update_end(&rx_ring->syncp);
        rx_ring->q_vector->rx.total_packets += total_rx_packets;
        rx_ring->q_vector->rx.total_bytes += total_rx_bytes;

        /* guarantee a trip back through this routine if there was a failure */
        return failure ? budget : (int)total_rx_packets;
}

static u32 i40e_buildreg_itr(const int type, const u16 itr)
{
        u32 val;

        val = I40E_VFINT_DYN_CTLN1_INTENA_MASK |
              /* Don't clear PBA because that can cause lost interrupts that
               * came in while we were cleaning/polling
               */
              (type << I40E_VFINT_DYN_CTLN1_ITR_INDX_SHIFT) |
              (itr << I40E_VFINT_DYN_CTLN1_INTERVAL_SHIFT);

        return val;
}

/* a small macro to shorten up some long lines */
#define INTREG I40E_VFINT_DYN_CTLN1
static inline int get_rx_itr(struct i40e_vsi *vsi, int idx)
{
        struct i40evf_adapter *adapter = vsi->back;

        return adapter->rx_rings[idx].rx_itr_setting;
}

static inline int get_tx_itr(struct i40e_vsi *vsi, int idx)
{
        struct i40evf_adapter *adapter = vsi->back;

        return adapter->tx_rings[idx].tx_itr_setting;
}

/**
 * i40e_update_enable_itr - Update itr and re-enable MSIX interrupt
 * @vsi: the VSI we care about
 * @q_vector: q_vector for which itr is being updated and interrupt enabled
 *
 **/
static inline void i40e_update_enable_itr(struct i40e_vsi *vsi,
                                          struct i40e_q_vector *q_vector)
{
        struct i40e_hw *hw = &vsi->back->hw;
        bool rx = false, tx = false;
        u32 rxval, txval;
        int vector;
        int idx = q_vector->v_idx;
        int rx_itr_setting, tx_itr_setting;

        vector = (q_vector->v_idx + vsi->base_vector);

        /* avoid dynamic calculation if in countdown mode OR if
         * all dynamic is disabled
         */
        rxval = txval = i40e_buildreg_itr(I40E_ITR_NONE, 0);

        rx_itr_setting = get_rx_itr(vsi, idx);
        tx_itr_setting = get_tx_itr(vsi, idx);

        if (q_vector->itr_countdown > 0 ||
            (!ITR_IS_DYNAMIC(rx_itr_setting) &&
             !ITR_IS_DYNAMIC(tx_itr_setting))) {
                goto enable_int;
        }

        if (ITR_IS_DYNAMIC(rx_itr_setting)) {
                rx = i40e_set_new_dynamic_itr(&q_vector->rx);
                rxval = i40e_buildreg_itr(I40E_RX_ITR, q_vector->rx.itr);
        }

        if (ITR_IS_DYNAMIC(tx_itr_setting)) {
                tx = i40e_set_new_dynamic_itr(&q_vector->tx);
                txval = i40e_buildreg_itr(I40E_TX_ITR, q_vector->tx.itr);
        }

        if (rx || tx) {
                /* get the higher of the two ITR adjustments and
                 * use the same value for both ITR registers
                 * when in adaptive mode (Rx and/or Tx)
                 */
                u16 itr = max(q_vector->tx.itr, q_vector->rx.itr);

                q_vector->tx.itr = q_vector->rx.itr = itr;
                txval = i40e_buildreg_itr(I40E_TX_ITR, itr);
                tx = true;
                rxval = i40e_buildreg_itr(I40E_RX_ITR, itr);
                rx = true;
        }

        /* only need to enable the interrupt once, but need
         * to possibly update both ITR values
         */
        if (rx) {
                /* set the INTENA_MSK_MASK so that this first write
                 * won't actually enable the interrupt, instead just
                 * updating the ITR (it's bit 31 PF and VF)
                 */
                rxval |= BIT(31);
                /* don't check _DOWN because interrupt isn't being enabled */
                wr32(hw, INTREG(vector - 1), rxval);
        }

enable_int:
        if (!test_bit(__I40E_VSI_DOWN, vsi->state))
                wr32(hw, INTREG(vector - 1), txval);

        if (q_vector->itr_countdown)
                q_vector->itr_countdown--;
        else
                q_vector->itr_countdown = ITR_COUNTDOWN_START;
}

/**
 * i40evf_napi_poll - NAPI polling Rx/Tx cleanup routine
 * @napi: napi struct with our devices info in it
 * @budget: amount of work driver is allowed to do this pass, in packets
 *
 * This function will clean all queues associated with a q_vector.
 *
 * Returns the amount of work done
 **/
int i40evf_napi_poll(struct napi_struct *napi, int budget)
{
        struct i40e_q_vector *q_vector =
                               container_of(napi, struct i40e_q_vector, napi);
        struct i40e_vsi *vsi = q_vector->vsi;
        struct i40e_ring *ring;
        bool clean_complete = true;
        bool arm_wb = false;
        int budget_per_ring;
        int work_done = 0;

        if (test_bit(__I40E_VSI_DOWN, vsi->state)) {
                napi_complete(napi);
                return 0;
        }

        /* Since the actual Tx work is minimal, we can give the Tx a larger
         * budget and be more aggressive about cleaning up the Tx descriptors.
         */
        i40e_for_each_ring(ring, q_vector->tx) {
                if (!i40e_clean_tx_irq(vsi, ring, budget)) {
                        clean_complete = false;
                        continue;
                }
                arm_wb |= ring->arm_wb;
                ring->arm_wb = false;
        }

        /* Handle case where we are called by netpoll with a budget of 0 */
        if (budget <= 0)
                goto tx_only;

        /* We attempt to distribute budget to each Rx queue fairly, but don't
         * allow the budget to go below 1 because that would exit polling early.
         */
        budget_per_ring = max(budget/q_vector->num_ringpairs, 1);

        i40e_for_each_ring(ring, q_vector->rx) {
                int cleaned = i40e_clean_rx_irq(ring, budget_per_ring);

                work_done += cleaned;
                /* if we clean as many as budgeted, we must not be done */
                if (cleaned >= budget_per_ring)
                        clean_complete = false;
        }

        /* If work not completed, return budget and polling will return */
        if (!clean_complete) {
                int cpu_id = smp_processor_id();

                /* It is possible that the interrupt affinity has changed but,
                 * if the cpu is pegged at 100%, polling will never exit while
                 * traffic continues and the interrupt will be stuck on this
                 * cpu.  We check to make sure affinity is correct before we
                 * continue to poll, otherwise we must stop polling so the
                 * interrupt can move to the correct cpu.
                 */
                if (!cpumask_test_cpu(cpu_id, &q_vector->affinity_mask)) {
                        /* Tell napi that we are done polling */
                        napi_complete_done(napi, work_done);

                        /* Force an interrupt */
                        i40evf_force_wb(vsi, q_vector);

                        /* Return budget-1 so that polling stops */
                        return budget - 1;
                }
tx_only:
                if (arm_wb) {
                        q_vector->tx.ring[0].tx_stats.tx_force_wb++;
                        i40e_enable_wb_on_itr(vsi, q_vector);
                }
                return budget;
        }

        if (vsi->back->flags & I40E_TXR_FLAGS_WB_ON_ITR)
                q_vector->arm_wb_state = false;

        /* Work is done so exit the polling mode and re-enable the interrupt */
        napi_complete_done(napi, work_done);

        i40e_update_enable_itr(vsi, q_vector);

        return min(work_done, budget - 1);
}

/**
 * i40evf_tx_prepare_vlan_flags - prepare generic TX VLAN tagging flags for HW
 * @skb:     send buffer
 * @tx_ring: ring to send buffer on
 * @flags:   the tx flags to be set
 *
 * Checks the skb and set up correspondingly several generic transmit flags
 * related to VLAN tagging for the HW, such as VLAN, DCB, etc.
 *
 * Returns error code indicate the frame should be dropped upon error and the
 * otherwise  returns 0 to indicate the flags has been set properly.
 **/
static inline int i40evf_tx_prepare_vlan_flags(struct sk_buff *skb,
                                               struct i40e_ring *tx_ring,
                                               u32 *flags)
{
        __be16 protocol = skb->protocol;
        u32  tx_flags = 0;

        if (protocol == htons(ETH_P_8021Q) &&
            !(tx_ring->netdev->features & NETIF_F_HW_VLAN_CTAG_TX)) {
                /* When HW VLAN acceleration is turned off by the user the
                 * stack sets the protocol to 8021q so that the driver
                 * can take any steps required to support the SW only
                 * VLAN handling.  In our case the driver doesn't need
                 * to take any further steps so just set the protocol
                 * to the encapsulated ethertype.
                 */
                skb->protocol = vlan_get_protocol(skb);
                goto out;
        }

        /* if we have a HW VLAN tag being added, default to the HW one */
        if (skb_vlan_tag_present(skb)) {
                tx_flags |= skb_vlan_tag_get(skb) << I40E_TX_FLAGS_VLAN_SHIFT;
                tx_flags |= I40E_TX_FLAGS_HW_VLAN;
        /* else if it is a SW VLAN, check the next protocol and store the tag */
        } else if (protocol == htons(ETH_P_8021Q)) {
                struct vlan_hdr *vhdr, _vhdr;

                vhdr = skb_header_pointer(skb, ETH_HLEN, sizeof(_vhdr), &_vhdr);
                if (!vhdr)
                        return -EINVAL;

                protocol = vhdr->h_vlan_encapsulated_proto;
                tx_flags |= ntohs(vhdr->h_vlan_TCI) << I40E_TX_FLAGS_VLAN_SHIFT;
                tx_flags |= I40E_TX_FLAGS_SW_VLAN;
        }

out:
        *flags = tx_flags;
        return 0;
}

/**
 * i40e_tso - set up the tso context descriptor
 * @first:    pointer to first Tx buffer for xmit
 * @hdr_len:  ptr to the size of the packet header
 * @cd_type_cmd_tso_mss: Quad Word 1
 *
 * Returns 0 if no TSO can happen, 1 if tso is going, or error
 **/
static int i40e_tso(struct i40e_tx_buffer *first, u8 *hdr_len,
                    u64 *cd_type_cmd_tso_mss)
{
        struct sk_buff *skb = first->skb;
        u64 cd_cmd, cd_tso_len, cd_mss;
        union {
                struct iphdr *v4;
                struct ipv6hdr *v6;
                unsigned char *hdr;
        } ip;
        union {
                struct tcphdr *tcp;
                struct udphdr *udp;
                unsigned char *hdr;
        } l4;
        u32 paylen, l4_offset;
        u16 gso_segs, gso_size;
        int err;

        if (skb->ip_summed != CHECKSUM_PARTIAL)
                return 0;

        if (!skb_is_gso(skb))
                return 0;

        err = skb_cow_head(skb, 0);
        if (err < 0)
                return err;

        ip.hdr = skb_network_header(skb);
        l4.hdr = skb_transport_header(skb);

        /* initialize outer IP header fields */
        if (ip.v4->version == 4) {
                ip.v4->tot_len = 0;
                ip.v4->check = 0;
        } else {
                ip.v6->payload_len = 0;
        }

        if (skb_shinfo(skb)->gso_type & (SKB_GSO_GRE |
                                         SKB_GSO_GRE_CSUM |
                                         SKB_GSO_IPXIP4 |
                                         SKB_GSO_IPXIP6 |
                                         SKB_GSO_UDP_TUNNEL |
                                         SKB_GSO_UDP_TUNNEL_CSUM)) {
                if (!(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL) &&
                    (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM)) {
                        l4.udp->len = 0;

                        /* determine offset of outer transport header */
                        l4_offset = l4.hdr - skb->data;

                        /* remove payload length from outer checksum */
                        paylen = skb->len - l4_offset;
                        csum_replace_by_diff(&l4.udp->check,
                                             (__force __wsum)htonl(paylen));
                }

                /* reset pointers to inner headers */
                ip.hdr = skb_inner_network_header(skb);
                l4.hdr = skb_inner_transport_header(skb);

                /* initialize inner IP header fields */
                if (ip.v4->version == 4) {
                        ip.v4->tot_len = 0;
                        ip.v4->check = 0;
                } else {
                        ip.v6->payload_len = 0;
                }
        }

        /* determine offset of inner transport header */
        l4_offset = l4.hdr - skb->data;

        /* remove payload length from inner checksum */
        paylen = skb->len - l4_offset;
        csum_replace_by_diff(&l4.tcp->check, (__force __wsum)htonl(paylen));

        /* compute length of segmentation header */
        *hdr_len = (l4.tcp->doff * 4) + l4_offset;

        /* pull values out of skb_shinfo */
        gso_size = skb_shinfo(skb)->gso_size;
        gso_segs = skb_shinfo(skb)->gso_segs;

        /* update GSO size and bytecount with header size */
        first->gso_segs = gso_segs;
        first->bytecount += (first->gso_segs - 1) * *hdr_len;

        /* find the field values */
        cd_cmd = I40E_TX_CTX_DESC_TSO;
        cd_tso_len = skb->len - *hdr_len;
        cd_mss = gso_size;
        *cd_type_cmd_tso_mss |= (cd_cmd << I40E_TXD_CTX_QW1_CMD_SHIFT) |
                                (cd_tso_len << I40E_TXD_CTX_QW1_TSO_LEN_SHIFT) |
                                (cd_mss << I40E_TXD_CTX_QW1_MSS_SHIFT);
        return 1;
}

/**
 * i40e_tx_enable_csum - Enable Tx checksum offloads
 * @skb: send buffer
 * @tx_flags: pointer to Tx flags currently set
 * @td_cmd: Tx descriptor command bits to set
 * @td_offset: Tx descriptor header offsets to set
 * @tx_ring: Tx descriptor ring
 * @cd_tunneling: ptr to context desc bits
 **/
static int i40e_tx_enable_csum(struct sk_buff *skb, u32 *tx_flags,
                               u32 *td_cmd, u32 *td_offset,
                               struct i40e_ring *tx_ring,
                               u32 *cd_tunneling)
{
        union {
                struct iphdr *v4;
                struct ipv6hdr *v6;
                unsigned char *hdr;
        } ip;
        union {
                struct tcphdr *tcp;
                struct udphdr *udp;
                unsigned char *hdr;
        } l4;
        unsigned char *exthdr;
        u32 offset, cmd = 0;
        __be16 frag_off;
        u8 l4_proto = 0;

        if (skb->ip_summed != CHECKSUM_PARTIAL)
                return 0;

        ip.hdr = skb_network_header(skb);
        l4.hdr = skb_transport_header(skb);

        /* compute outer L2 header size */
        offset = ((ip.hdr - skb->data) / 2) << I40E_TX_DESC_LENGTH_MACLEN_SHIFT;

        if (skb->encapsulation) {
                u32 tunnel = 0;
                /* define outer network header type */
                if (*tx_flags & I40E_TX_FLAGS_IPV4) {
                        tunnel |= (*tx_flags & I40E_TX_FLAGS_TSO) ?
                                  I40E_TX_CTX_EXT_IP_IPV4 :
                                  I40E_TX_CTX_EXT_IP_IPV4_NO_CSUM;

                        l4_proto = ip.v4->protocol;
                } else if (*tx_flags & I40E_TX_FLAGS_IPV6) {
                        tunnel |= I40E_TX_CTX_EXT_IP_IPV6;

                        exthdr = ip.hdr + sizeof(*ip.v6);
                        l4_proto = ip.v6->nexthdr;
                        if (l4.hdr != exthdr)
                                ipv6_skip_exthdr(skb, exthdr - skb->data,
                                                 &l4_proto, &frag_off);
                }

                /* define outer transport */
                switch (l4_proto) {
                case IPPROTO_UDP:
                        tunnel |= I40E_TXD_CTX_UDP_TUNNELING;
                        *tx_flags |= I40E_TX_FLAGS_VXLAN_TUNNEL;
                        break;
                case IPPROTO_GRE:
                        tunnel |= I40E_TXD_CTX_GRE_TUNNELING;
                        *tx_flags |= I40E_TX_FLAGS_VXLAN_TUNNEL;
                        break;
                case IPPROTO_IPIP:
                case IPPROTO_IPV6:
                        *tx_flags |= I40E_TX_FLAGS_VXLAN_TUNNEL;
                        l4.hdr = skb_inner_network_header(skb);
                        break;
                default:
                        if (*tx_flags & I40E_TX_FLAGS_TSO)
                                return -1;

                        skb_checksum_help(skb);
                        return 0;
                }

                /* compute outer L3 header size */
                tunnel |= ((l4.hdr - ip.hdr) / 4) <<
                          I40E_TXD_CTX_QW0_EXT_IPLEN_SHIFT;

                /* switch IP header pointer from outer to inner header */
                ip.hdr = skb_inner_network_header(skb);

                /* compute tunnel header size */
                tunnel |= ((ip.hdr - l4.hdr) / 2) <<
                          I40E_TXD_CTX_QW0_NATLEN_SHIFT;

                /* indicate if we need to offload outer UDP header */
                if ((*tx_flags & I40E_TX_FLAGS_TSO) &&
                    !(skb_shinfo(skb)->gso_type & SKB_GSO_PARTIAL) &&
                    (skb_shinfo(skb)->gso_type & SKB_GSO_UDP_TUNNEL_CSUM))
                        tunnel |= I40E_TXD_CTX_QW0_L4T_CS_MASK;

                /* record tunnel offload values */
                *cd_tunneling |= tunnel;

                /* switch L4 header pointer from outer to inner */
                l4.hdr = skb_inner_transport_header(skb);
                l4_proto = 0;

                /* reset type as we transition from outer to inner headers */
                *tx_flags &= ~(I40E_TX_FLAGS_IPV4 | I40E_TX_FLAGS_IPV6);
                if (ip.v4->version == 4)
                        *tx_flags |= I40E_TX_FLAGS_IPV4;
                if (ip.v6->version == 6)
                        *tx_flags |= I40E_TX_FLAGS_IPV6;
        }

        /* Enable IP checksum offloads */
        if (*tx_flags & I40E_TX_FLAGS_IPV4) {
                l4_proto = ip.v4->protocol;
                /* the stack computes the IP header already, the only time we
                 * need the hardware to recompute it is in the case of TSO.
                 */
                cmd |= (*tx_flags & I40E_TX_FLAGS_TSO) ?
                       I40E_TX_DESC_CMD_IIPT_IPV4_CSUM :
                       I40E_TX_DESC_CMD_IIPT_IPV4;
        } else if (*tx_flags & I40E_TX_FLAGS_IPV6) {
                cmd |= I40E_TX_DESC_CMD_IIPT_IPV6;

                exthdr = ip.hdr + sizeof(*ip.v6);
                l4_proto = ip.v6->nexthdr;
                if (l4.hdr != exthdr)
                        ipv6_skip_exthdr(skb, exthdr - skb->data,
                                         &l4_proto, &frag_off);
        }

        /* compute inner L3 header size */
        offset |= ((l4.hdr - ip.hdr) / 4) << I40E_TX_DESC_LENGTH_IPLEN_SHIFT;

        /* Enable L4 checksum offloads */
        switch (l4_proto) {
        case IPPROTO_TCP:
                /* enable checksum offloads */
                cmd |= I40E_TX_DESC_CMD_L4T_EOFT_TCP;
                offset |= l4.tcp->doff << I40E_TX_DESC_LENGTH_L4_FC_LEN_SHIFT;
                break;
        case IPPROTO_SCTP:
                /* enable SCTP checksum offload */
                cmd |= I40E_TX_DESC_CMD_L4T_EOFT_SCTP;
                offset |= (sizeof(struct sctphdr) >> 2) <<
                          I40E_TX_DESC_LENGTH_L4_FC_LEN_SHIFT;
                break;
        case IPPROTO_UDP:
                /* enable UDP checksum offload */
                cmd |= I40E_TX_DESC_CMD_L4T_EOFT_UDP;
                offset |= (sizeof(struct udphdr) >> 2) <<
                          I40E_TX_DESC_LENGTH_L4_FC_LEN_SHIFT;
                break;
        default:
                if (*tx_flags & I40E_TX_FLAGS_TSO)
                        return -1;
                skb_checksum_help(skb);
                return 0;
        }

        *td_cmd |= cmd;
        *td_offset |= offset;

        return 1;
}

/**
 * i40e_create_tx_ctx Build the Tx context descriptor
 * @tx_ring:  ring to create the descriptor on
 * @cd_type_cmd_tso_mss: Quad Word 1
 * @cd_tunneling: Quad Word 0 - bits 0-31
 * @cd_l2tag2: Quad Word 0 - bits 32-63
 **/
static void i40e_create_tx_ctx(struct i40e_ring *tx_ring,
                               const u64 cd_type_cmd_tso_mss,
                               const u32 cd_tunneling, const u32 cd_l2tag2)
{
        struct i40e_tx_context_desc *context_desc;
        int i = tx_ring->next_to_use;

        if ((cd_type_cmd_tso_mss == I40E_TX_DESC_DTYPE_CONTEXT) &&
            !cd_tunneling && !cd_l2tag2)
                return;

        /* grab the next descriptor */
        context_desc = I40E_TX_CTXTDESC(tx_ring, i);

        i++;
        tx_ring->next_to_use = (i < tx_ring->count) ? i : 0;

        /* cpu_to_le32 and assign to struct fields */
        context_desc->tunneling_params = cpu_to_le32(cd_tunneling);
        context_desc->l2tag2 = cpu_to_le16(cd_l2tag2);
        context_desc->rsvd = cpu_to_le16(0);
        context_desc->type_cmd_tso_mss = cpu_to_le64(cd_type_cmd_tso_mss);
}

/**
 * __i40evf_chk_linearize - Check if there are more than 8 buffers per packet
 * @skb:      send buffer
 *
 * Note: Our HW can't DMA more than 8 buffers to build a packet on the wire
 * and so we need to figure out the cases where we need to linearize the skb.
 *
 * For TSO we need to count the TSO header and segment payload separately.
 * As such we need to check cases where we have 7 fragments or more as we
 * can potentially require 9 DMA transactions, 1 for the TSO header, 1 for
 * the segment payload in the first descriptor, and another 7 for the
 * fragments.
 **/
bool __i40evf_chk_linearize(struct sk_buff *skb)
{
        const struct skb_frag_struct *frag, *stale;
        int nr_frags, sum;

        /* no need to check if number of frags is less than 7 */
        nr_frags = skb_shinfo(skb)->nr_frags;
        if (nr_frags < (I40E_MAX_BUFFER_TXD - 1))
                return false;

        /* We need to walk through the list and validate that each group
         * of 6 fragments totals at least gso_size.
         */
        nr_frags -= I40E_MAX_BUFFER_TXD - 2;
        frag = &skb_shinfo(skb)->frags[0];

        /* Initialize size to the negative value of gso_size minus 1.  We
         * use this as the worst case scenerio in which the frag ahead
         * of us only provides one byte which is why we are limited to 6
         * descriptors for a single transmit as the header and previous
         * fragment are already consuming 2 descriptors.
         */
        sum = 1 - skb_shinfo(skb)->gso_size;

        /* Add size of frags 0 through 4 to create our initial sum */
        sum += skb_frag_size(frag++);
        sum += skb_frag_size(frag++);
        sum += skb_frag_size(frag++);
        sum += skb_frag_size(frag++);
        sum += skb_frag_size(frag++);

        /* Walk through fragments adding latest fragment, testing it, and
         * then removing stale fragments from the sum.
         */
        for (stale = &skb_shinfo(skb)->frags[0];; stale++) {
                int stale_size = skb_frag_size(stale);

                sum += skb_frag_size(frag++);

                /* The stale fragment may present us with a smaller
                 * descriptor than the actual fragment size. To account
                 * for that we need to remove all the data on the front and
                 * figure out what the remainder would be in the last
                 * descriptor associated with the fragment.
                 */
                if (stale_size > I40E_MAX_DATA_PER_TXD) {
                        int align_pad = -(stale->page_offset) &
                                        (I40E_MAX_READ_REQ_SIZE - 1);

                        sum -= align_pad;
                        stale_size -= align_pad;

                        do {
                                sum -= I40E_MAX_DATA_PER_TXD_ALIGNED;
                                stale_size -= I40E_MAX_DATA_PER_TXD_ALIGNED;
                        } while (stale_size > I40E_MAX_DATA_PER_TXD);
                }

                /* if sum is negative we failed to make sufficient progress */
                if (sum < 0)
                        return true;

                if (!nr_frags--)
                        break;

                sum -= stale_size;
        }

        return false;
}

/**
 * __i40evf_maybe_stop_tx - 2nd level check for tx stop conditions
 * @tx_ring: the ring to be checked
 * @size:    the size buffer we want to assure is available
 *
 * Returns -EBUSY if a stop is needed, else 0
 **/
int __i40evf_maybe_stop_tx(struct i40e_ring *tx_ring, int size)
{
        netif_stop_subqueue(tx_ring->netdev, tx_ring->queue_index);
        /* Memory barrier before checking head and tail */
        smp_mb();

        /* Check again in a case another CPU has just made room available. */
        if (likely(I40E_DESC_UNUSED(tx_ring) < size))
                return -EBUSY;

        /* A reprieve! - use start_queue because it doesn't call schedule */
        netif_start_subqueue(tx_ring->netdev, tx_ring->queue_index);
        ++tx_ring->tx_stats.restart_queue;
        return 0;
}

/**
 * i40evf_tx_map - Build the Tx descriptor
 * @tx_ring:  ring to send buffer on
 * @skb:      send buffer
 * @first:    first buffer info buffer to use
 * @tx_flags: collected send information
 * @hdr_len:  size of the packet header
 * @td_cmd:   the command field in the descriptor
 * @td_offset: offset for checksum or crc
 **/
static inline void i40evf_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
                                 struct i40e_tx_buffer *first, u32 tx_flags,
                                 const u8 hdr_len, u32 td_cmd, u32 td_offset)
{
        unsigned int data_len = skb->data_len;
        unsigned int size = skb_headlen(skb);
        struct skb_frag_struct *frag;
        struct i40e_tx_buffer *tx_bi;
        struct i40e_tx_desc *tx_desc;
        u16 i = tx_ring->next_to_use;
        u32 td_tag = 0;
        dma_addr_t dma;

        if (tx_flags & I40E_TX_FLAGS_HW_VLAN) {
                td_cmd |= I40E_TX_DESC_CMD_IL2TAG1;
                td_tag = (tx_flags & I40E_TX_FLAGS_VLAN_MASK) >>
                         I40E_TX_FLAGS_VLAN_SHIFT;
        }

        first->tx_flags = tx_flags;

        dma = dma_map_single(tx_ring->dev, skb->data, size, DMA_TO_DEVICE);

        tx_desc = I40E_TX_DESC(tx_ring, i);
        tx_bi = first;

        for (frag = &skb_shinfo(skb)->frags[0];; frag++) {
                unsigned int max_data = I40E_MAX_DATA_PER_TXD_ALIGNED;

                if (dma_mapping_error(tx_ring->dev, dma))
                        goto dma_error;

                /* record length, and DMA address */
                dma_unmap_len_set(tx_bi, len, size);
                dma_unmap_addr_set(tx_bi, dma, dma);

                /* align size to end of page */
                max_data += -dma & (I40E_MAX_READ_REQ_SIZE - 1);
                tx_desc->buffer_addr = cpu_to_le64(dma);

                while (unlikely(size > I40E_MAX_DATA_PER_TXD)) {
                        tx_desc->cmd_type_offset_bsz =
                                build_ctob(td_cmd, td_offset,
                                           max_data, td_tag);

                        tx_desc++;
                        i++;

                        if (i == tx_ring->count) {
                                tx_desc = I40E_TX_DESC(tx_ring, 0);
                                i = 0;
                        }

                        dma += max_data;
                        size -= max_data;

                        max_data = I40E_MAX_DATA_PER_TXD_ALIGNED;
                        tx_desc->buffer_addr = cpu_to_le64(dma);
                }

                if (likely(!data_len))
                        break;

                tx_desc->cmd_type_offset_bsz = build_ctob(td_cmd, td_offset,
                                                          size, td_tag);

                tx_desc++;
                i++;

                if (i == tx_ring->count) {
                        tx_desc = I40E_TX_DESC(tx_ring, 0);
                        i = 0;
                }

                size = skb_frag_size(frag);
                data_len -= size;

                dma = skb_frag_dma_map(tx_ring->dev, frag, 0, size,
                                       DMA_TO_DEVICE);

                tx_bi = &tx_ring->tx_bi[i];
        }

        netdev_tx_sent_queue(txring_txq(tx_ring), first->bytecount);

        i++;
        if (i == tx_ring->count)
                i = 0;

        tx_ring->next_to_use = i;

        i40e_maybe_stop_tx(tx_ring, DESC_NEEDED);

        /* write last descriptor with RS and EOP bits */
        td_cmd |= I40E_TXD_CMD;
        tx_desc->cmd_type_offset_bsz =
                        build_ctob(td_cmd, td_offset, size, td_tag);

        /* Force memory writes to complete before letting h/w know there
         * are new descriptors to fetch.
         *
         * We also use this memory barrier to make certain all of the
         * status bits have been updated before next_to_watch is written.
         */
        wmb();

        /* set next_to_watch value indicating a packet is present */
        first->next_to_watch = tx_desc;

        /* notify HW of packet */
        if (netif_xmit_stopped(txring_txq(tx_ring)) || !skb->xmit_more) {
                writel(i, tx_ring->tail);

                /* we need this if more than one processor can write to our tail
                 * at a time, it synchronizes IO on IA64/Altix systems
                 */
                mmiowb();
        }

        return;

dma_error:
        dev_info(tx_ring->dev, "TX DMA map failed\n");

        /* clear dma mappings for failed tx_bi map */
        for (;;) {
                tx_bi = &tx_ring->tx_bi[i];
                i40e_unmap_and_free_tx_resource(tx_ring, tx_bi);
                if (tx_bi == first)
                        break;
                if (i == 0)
                        i = tx_ring->count;
                i--;
        }

        tx_ring->next_to_use = i;
}

/**
 * i40e_xmit_frame_ring - Sends buffer on Tx ring
 * @skb:     send buffer
 * @tx_ring: ring to send buffer on
 *
 * Returns NETDEV_TX_OK if sent, else an error code
 **/
static netdev_tx_t i40e_xmit_frame_ring(struct sk_buff *skb,
                                        struct i40e_ring *tx_ring)
{
        u64 cd_type_cmd_tso_mss = I40E_TX_DESC_DTYPE_CONTEXT;
        u32 cd_tunneling = 0, cd_l2tag2 = 0;
        struct i40e_tx_buffer *first;
        u32 td_offset = 0;
        u32 tx_flags = 0;
        __be16 protocol;
        u32 td_cmd = 0;
        u8 hdr_len = 0;
        int tso, count;

        /* prefetch the data, we'll need it later */
        prefetch(skb->data);

        i40e_trace(xmit_frame_ring, skb, tx_ring);

        count = i40e_xmit_descriptor_count(skb);
        if (i40e_chk_linearize(skb, count)) {
                if (__skb_linearize(skb)) {
                        dev_kfree_skb_any(skb);
                        return NETDEV_TX_OK;
                }
                count = i40e_txd_use_count(skb->len);
                tx_ring->tx_stats.tx_linearize++;
        }

        /* need: 1 descriptor per page * PAGE_SIZE/I40E_MAX_DATA_PER_TXD,
         *       + 1 desc for skb_head_len/I40E_MAX_DATA_PER_TXD,
         *       + 4 desc gap to avoid the cache line where head is,
         *       + 1 desc for context descriptor,
         * otherwise try next time
         */
        if (i40e_maybe_stop_tx(tx_ring, count + 4 + 1)) {
                tx_ring->tx_stats.tx_busy++;
                return NETDEV_TX_BUSY;
        }

        /* record the location of the first descriptor for this packet */
        first = &tx_ring->tx_bi[tx_ring->next_to_use];
        first->skb = skb;
        first->bytecount = skb->len;
        first->gso_segs = 1;

        /* prepare the xmit flags */
        if (i40evf_tx_prepare_vlan_flags(skb, tx_ring, &tx_flags))
                goto out_drop;

        /* obtain protocol of skb */
        protocol = vlan_get_protocol(skb);

        /* setup IPv4/IPv6 offloads */
        if (protocol == htons(ETH_P_IP))
                tx_flags |= I40E_TX_FLAGS_IPV4;
        else if (protocol == htons(ETH_P_IPV6))
                tx_flags |= I40E_TX_FLAGS_IPV6;

        tso = i40e_tso(first, &hdr_len, &cd_type_cmd_tso_mss);

        if (tso < 0)
                goto out_drop;
        else if (tso)
                tx_flags |= I40E_TX_FLAGS_TSO;

        /* Always offload the checksum, since it's in the data descriptor */
        tso = i40e_tx_enable_csum(skb, &tx_flags, &td_cmd, &td_offset,
                                  tx_ring, &cd_tunneling);
        if (tso < 0)
                goto out_drop;

        skb_tx_timestamp(skb);

        /* always enable CRC insertion offload */
        td_cmd |= I40E_TX_DESC_CMD_ICRC;

        i40e_create_tx_ctx(tx_ring, cd_type_cmd_tso_mss,
                           cd_tunneling, cd_l2tag2);

        i40evf_tx_map(tx_ring, skb, first, tx_flags, hdr_len,
                      td_cmd, td_offset);

        return NETDEV_TX_OK;

out_drop:
        i40e_trace(xmit_frame_ring_drop, first->skb, tx_ring);
        dev_kfree_skb_any(first->skb);
        first->skb = NULL;
        return NETDEV_TX_OK;
}

/**
 * i40evf_xmit_frame - Selects the correct VSI and Tx queue to send buffer
 * @skb:    send buffer
 * @netdev: network interface device structure
 *
 * Returns NETDEV_TX_OK if sent, else an error code
 **/
netdev_tx_t i40evf_xmit_frame(struct sk_buff *skb, struct net_device *netdev)
{
        struct i40evf_adapter *adapter = netdev_priv(netdev);
        struct i40e_ring *tx_ring = &adapter->tx_rings[skb->queue_mapping];

        /* hardware can't handle really short frames, hardware padding works
         * beyond this point
         */
        if (unlikely(skb->len < I40E_MIN_TX_LEN)) {
                if (skb_pad(skb, I40E_MIN_TX_LEN - skb->len))
                        return NETDEV_TX_OK;
                skb->len = I40E_MIN_TX_LEN;
                skb_set_tail_pointer(skb, I40E_MIN_TX_LEN);
        }

        return i40e_xmit_frame_ring(skb, tx_ring);
}