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

[sfrench/cifs-2.6.git] / drivers / net / ethernet / intel / ice / ice_txrx.c

// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2018, Intel Corporation. */

/* The driver transmit and receive code */

#include <linux/prefetch.h>
#include <linux/mm.h>
#include "ice.h"

#define ICE_RX_HDR_SIZE         256

/**
 * ice_unmap_and_free_tx_buf - Release a Tx buffer
 * @ring: the ring that owns the buffer
 * @tx_buf: the buffer to free
 */
static void
ice_unmap_and_free_tx_buf(struct ice_ring *ring, struct ice_tx_buf *tx_buf)
{
        if (tx_buf->skb) {
                dev_kfree_skb_any(tx_buf->skb);
                if (dma_unmap_len(tx_buf, len))
                        dma_unmap_single(ring->dev,
                                         dma_unmap_addr(tx_buf, dma),
                                         dma_unmap_len(tx_buf, len),
                                         DMA_TO_DEVICE);
        } else if (dma_unmap_len(tx_buf, len)) {
                dma_unmap_page(ring->dev,
                               dma_unmap_addr(tx_buf, dma),
                               dma_unmap_len(tx_buf, len),
                               DMA_TO_DEVICE);
        }

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

static struct netdev_queue *txring_txq(const struct ice_ring *ring)
{
        return netdev_get_tx_queue(ring->netdev, ring->q_index);
}

/**
 * ice_clean_tx_ring - Free any empty Tx buffers
 * @tx_ring: ring to be cleaned
 */
void ice_clean_tx_ring(struct ice_ring *tx_ring)
{
        u16 i;

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

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

        memset(tx_ring->tx_buf, 0, sizeof(*tx_ring->tx_buf) * tx_ring->count);

        /* 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));
}

/**
 * ice_free_tx_ring - Free Tx resources per queue
 * @tx_ring: Tx descriptor ring for a specific queue
 *
 * Free all transmit software resources
 */
void ice_free_tx_ring(struct ice_ring *tx_ring)
{
        ice_clean_tx_ring(tx_ring);
        devm_kfree(tx_ring->dev, tx_ring->tx_buf);
        tx_ring->tx_buf = NULL;

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

/**
 * ice_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 ice_clean_tx_irq(struct ice_vsi *vsi, struct ice_ring *tx_ring,
                             int napi_budget)
{
        unsigned int total_bytes = 0, total_pkts = 0;
        unsigned int budget = vsi->work_lmt;
        s16 i = tx_ring->next_to_clean;
        struct ice_tx_desc *tx_desc;
        struct ice_tx_buf *tx_buf;

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

        do {
                struct ice_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;

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

                /* if the descriptor isn't done, no work yet to do */
                if (!(eop_desc->cmd_type_offset_bsz &
                      cpu_to_le64(ICE_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_pkts += 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_buf data */
                tx_buf->skb = NULL;
                dma_unmap_len_set(tx_buf, len, 0);

                /* unmap remaining buffers */
                while (tx_desc != eop_desc) {
                        tx_buf++;
                        tx_desc++;
                        i++;
                        if (unlikely(!i)) {
                                i -= tx_ring->count;
                                tx_buf = tx_ring->tx_buf;
                                tx_desc = ICE_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_buf;
                        tx_desc = ICE_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.pkts += total_pkts;
        u64_stats_update_end(&tx_ring->syncp);
        tx_ring->q_vector->tx.total_bytes += total_bytes;
        tx_ring->q_vector->tx.total_pkts += total_pkts;

        netdev_tx_completed_queue(txring_txq(tx_ring), total_pkts,
                                  total_bytes);

#define TX_WAKE_THRESHOLD ((s16)(DESC_NEEDED * 2))
        if (unlikely(total_pkts && netif_carrier_ok(tx_ring->netdev) &&
                     (ICE_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->q_index) &&
                   !test_bit(__ICE_DOWN, vsi->state)) {
                        netif_wake_subqueue(tx_ring->netdev,
                                            tx_ring->q_index);
                        ++tx_ring->tx_stats.restart_q;
                }
        }

        return !!budget;
}

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

        if (!dev)
                return -ENOMEM;

        /* warn if we are about to overwrite the pointer */
        WARN_ON(tx_ring->tx_buf);
        tx_ring->tx_buf =
                devm_kzalloc(dev, sizeof(*tx_ring->tx_buf) * tx_ring->count,
                             GFP_KERNEL);
        if (!tx_ring->tx_buf)
                return -ENOMEM;

        /* round up to nearest 4K */
        tx_ring->size = ALIGN(tx_ring->count * sizeof(struct ice_tx_desc),
                              4096);
        tx_ring->desc = dmam_alloc_coherent(dev, tx_ring->size, &tx_ring->dma,
                                            GFP_KERNEL);
        if (!tx_ring->desc) {
                dev_err(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;
        tx_ring->tx_stats.prev_pkt = -1;
        return 0;

err:
        devm_kfree(dev, tx_ring->tx_buf);
        tx_ring->tx_buf = NULL;
        return -ENOMEM;
}

/**
 * ice_clean_rx_ring - Free Rx buffers
 * @rx_ring: ring to be cleaned
 */
void ice_clean_rx_ring(struct ice_ring *rx_ring)
{
        struct device *dev = rx_ring->dev;
        u16 i;

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

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

                if (rx_buf->skb) {
                        dev_kfree_skb(rx_buf->skb);
                        rx_buf->skb = NULL;
                }
                if (!rx_buf->page)
                        continue;

                dma_unmap_page(dev, rx_buf->dma, PAGE_SIZE, DMA_FROM_DEVICE);
                __free_pages(rx_buf->page, 0);

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

        memset(rx_ring->rx_buf, 0, sizeof(*rx_ring->rx_buf) * rx_ring->count);

        /* 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;
}

/**
 * ice_free_rx_ring - Free Rx resources
 * @rx_ring: ring to clean the resources from
 *
 * Free all receive software resources
 */
void ice_free_rx_ring(struct ice_ring *rx_ring)
{
        ice_clean_rx_ring(rx_ring);
        devm_kfree(rx_ring->dev, rx_ring->rx_buf);
        rx_ring->rx_buf = NULL;

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

/**
 * ice_setup_rx_ring - Allocate the Rx descriptors
 * @rx_ring: the Rx ring to set up
 *
 * Return 0 on success, negative on error
 */
int ice_setup_rx_ring(struct ice_ring *rx_ring)
{
        struct device *dev = rx_ring->dev;

        if (!dev)
                return -ENOMEM;

        /* warn if we are about to overwrite the pointer */
        WARN_ON(rx_ring->rx_buf);
        rx_ring->rx_buf =
                devm_kzalloc(dev, sizeof(*rx_ring->rx_buf) * rx_ring->count,
                             GFP_KERNEL);
        if (!rx_ring->rx_buf)
                return -ENOMEM;

        /* round up to nearest 4K */
        rx_ring->size = rx_ring->count * sizeof(union ice_32byte_rx_desc);
        rx_ring->size = ALIGN(rx_ring->size, 4096);
        rx_ring->desc = dmam_alloc_coherent(dev, rx_ring->size, &rx_ring->dma,
                                            GFP_KERNEL);
        if (!rx_ring->desc) {
                dev_err(dev, "Unable to allocate memory for the Rx descriptor ring, size=%d\n",
                        rx_ring->size);
                goto err;
        }

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

err:
        devm_kfree(dev, rx_ring->rx_buf);
        rx_ring->rx_buf = NULL;
        return -ENOMEM;
}

/**
 * ice_release_rx_desc - Store the new tail and head values
 * @rx_ring: ring to bump
 * @val: new head index
 */
static void ice_release_rx_desc(struct ice_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);
}

/**
 * ice_alloc_mapped_page - recycle or make a new page
 * @rx_ring: ring to use
 * @bi: rx_buf struct to modify
 *
 * Returns true if the page was successfully allocated or
 * reused.
 */
static bool ice_alloc_mapped_page(struct ice_ring *rx_ring,
                                  struct ice_rx_buf *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 = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
        if (unlikely(!page)) {
                rx_ring->rx_stats.alloc_page_failed++;
                return false;
        }

        /* map page for use */
        dma = dma_map_page(rx_ring->dev, page, 0, PAGE_SIZE, DMA_FROM_DEVICE);

        /* 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, 0);
                rx_ring->rx_stats.alloc_page_failed++;
                return false;
        }

        bi->dma = dma;
        bi->page = page;
        bi->page_offset = 0;

        return true;
}

/**
 * ice_alloc_rx_bufs - 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 ice_alloc_rx_bufs(struct ice_ring *rx_ring, u16 cleaned_count)
{
        union ice_32b_rx_flex_desc *rx_desc;
        u16 ntu = rx_ring->next_to_use;
        struct ice_rx_buf *bi;

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

        /* get the RX descriptor and buffer based on next_to_use */
        rx_desc = ICE_RX_DESC(rx_ring, ntu);
        bi = &rx_ring->rx_buf[ntu];

        do {
                if (!ice_alloc_mapped_page(rx_ring, bi))
                        goto no_bufs;

                /* 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 = ICE_RX_DESC(rx_ring, 0);
                        bi = rx_ring->rx_buf;
                        ntu = 0;
                }

                /* clear the status bits for the next_to_use descriptor */
                rx_desc->wb.status_error0 = 0;

                cleaned_count--;
        } while (cleaned_count);

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

        return false;

no_bufs:
        if (rx_ring->next_to_use != ntu)
                ice_release_rx_desc(rx_ring, ntu);

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

/**
 * ice_page_is_reserved - check if reuse is possible
 * @page: page struct to check
 */
static bool ice_page_is_reserved(struct page *page)
{
        return (page_to_nid(page) != numa_mem_id()) || page_is_pfmemalloc(page);
}

/**
 * ice_add_rx_frag - Add contents of Rx buffer to sk_buff
 * @rx_buf: buffer containing page to add
 * @rx_desc: descriptor containing length of buffer written by hardware
 * @skb: sk_buf to place the data into
 *
 * This function will add the data contained in rx_buf->page to the skb.
 * This is done either through a direct copy if the data in the buffer is
 * less than the skb header size, otherwise it will just attach the page as
 * a frag to the skb.
 *
 * The function will then update the page offset if necessary and return
 * true if the buffer can be reused by the adapter.
 */
static bool ice_add_rx_frag(struct ice_rx_buf *rx_buf,
                            union ice_32b_rx_flex_desc *rx_desc,
                            struct sk_buff *skb)
{
#if (PAGE_SIZE < 8192)
        unsigned int truesize = ICE_RXBUF_2048;
#else
        unsigned int last_offset = PAGE_SIZE - ICE_RXBUF_2048;
        unsigned int truesize;
#endif /* PAGE_SIZE < 8192) */

        struct page *page;
        unsigned int size;

        size = le16_to_cpu(rx_desc->wb.pkt_len) &
                ICE_RX_FLX_DESC_PKT_LEN_M;

        page = rx_buf->page;

#if (PAGE_SIZE >= 8192)
        truesize = ALIGN(size, L1_CACHE_BYTES);
#endif /* PAGE_SIZE >= 8192) */

        /* will the data fit in the skb we allocated? if so, just
         * copy it as it is pretty small anyway
         */
        if (size <= ICE_RX_HDR_SIZE && !skb_is_nonlinear(skb)) {
                unsigned char *va = page_address(page) + rx_buf->page_offset;

                memcpy(__skb_put(skb, size), va, ALIGN(size, sizeof(long)));

                /* page is not reserved, we can reuse buffer as-is */
                if (likely(!ice_page_is_reserved(page)))
                        return true;

                /* this page cannot be reused so discard it */
                __free_pages(page, 0);
                return false;
        }

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

        /* avoid re-using remote pages */
        if (unlikely(ice_page_is_reserved(page)))
                return false;

#if (PAGE_SIZE < 8192)
        /* if we are only owner of page we can reuse it */
        if (unlikely(page_count(page) != 1))
                return false;

        /* flip page offset to other buffer */
        rx_buf->page_offset ^= truesize;
#else
        /* move offset up to the next cache line */
        rx_buf->page_offset += truesize;

        if (rx_buf->page_offset > last_offset)
                return false;
#endif /* PAGE_SIZE < 8192) */

        /* Even if we own the page, we are not allowed to use atomic_set()
         * This would break get_page_unless_zero() users.
         */
        get_page(rx_buf->page);

        return true;
}

/**
 * ice_reuse_rx_page - page flip buffer and store it back on the ring
 * @rx_ring: Rx descriptor ring to store buffers on
 * @old_buf: donor buffer to have page reused
 *
 * Synchronizes page for reuse by the adapter
 */
static void ice_reuse_rx_page(struct ice_ring *rx_ring,
                              struct ice_rx_buf *old_buf)
{
        u16 nta = rx_ring->next_to_alloc;
        struct ice_rx_buf *new_buf;

        new_buf = &rx_ring->rx_buf[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_buf = *old_buf;
}

/**
 * ice_fetch_rx_buf - Allocate skb and populate it
 * @rx_ring: Rx descriptor ring to transact packets on
 * @rx_desc: descriptor containing info written by hardware
 *
 * This function allocates an skb on the fly, and populates it with the page
 * data from the current receive descriptor, taking care to set up the skb
 * correctly, as well as handling calling the page recycle function if
 * necessary.
 */
static struct sk_buff *ice_fetch_rx_buf(struct ice_ring *rx_ring,
                                        union ice_32b_rx_flex_desc *rx_desc)
{
        struct ice_rx_buf *rx_buf;
        struct sk_buff *skb;
        struct page *page;

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

        skb = rx_buf->skb;

        if (likely(!skb)) {
                u8 *page_addr = page_address(page) + rx_buf->page_offset;

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

                /* allocate a skb to store the frags */
                skb = __napi_alloc_skb(&rx_ring->q_vector->napi,
                                       ICE_RX_HDR_SIZE,
                                       GFP_ATOMIC | __GFP_NOWARN);
                if (unlikely(!skb)) {
                        rx_ring->rx_stats.alloc_buf_failed++;
                        return NULL;
                }

                /* we will be copying header into skb->data in
                 * pskb_may_pull so it is in our interest to prefetch
                 * it now to avoid a possible cache miss
                 */
                prefetchw(skb->data);

                skb_record_rx_queue(skb, rx_ring->q_index);
        } else {
                /* we are reusing so sync this buffer for CPU use */
                dma_sync_single_range_for_cpu(rx_ring->dev, rx_buf->dma,
                                              rx_buf->page_offset,
                                              ICE_RXBUF_2048,
                                              DMA_FROM_DEVICE);

                rx_buf->skb = NULL;
        }

        /* pull page into skb */
        if (ice_add_rx_frag(rx_buf, rx_desc, skb)) {
                /* hand second half of page back to the ring */
                ice_reuse_rx_page(rx_ring, rx_buf);
                rx_ring->rx_stats.page_reuse_count++;
        } else {
                /* we are not reusing the buffer so unmap it */
                dma_unmap_page(rx_ring->dev, rx_buf->dma, PAGE_SIZE,
                               DMA_FROM_DEVICE);
        }

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

        return skb;
}

/**
 * ice_pull_tail - ice specific version of skb_pull_tail
 * @skb: pointer to current skb being adjusted
 *
 * This function is an ice specific version of __pskb_pull_tail. The
 * main difference between this version and the original function is that
 * this function can make several assumptions about the state of things
 * that allow for significant optimizations versus the standard function.
 * As a result we can do things like drop a frag and maintain an accurate
 * truesize for the skb.
 */
static void ice_pull_tail(struct sk_buff *skb)
{
        struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
        unsigned int pull_len;
        unsigned char *va;

        /* it is valid to use page_address instead of kmap since we are
         * working with pages allocated out of the lomem pool per
         * alloc_page(GFP_ATOMIC)
         */
        va = skb_frag_address(frag);

        /* we need the header to contain the greater of either ETH_HLEN or
         * 60 bytes if the skb->len is less than 60 for skb_pad.
         */
        pull_len = eth_get_headlen(va, ICE_RX_HDR_SIZE);

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

        /* update all of the pointers */
        skb_frag_size_sub(frag, pull_len);
        frag->page_offset += pull_len;
        skb->data_len -= pull_len;
        skb->tail += pull_len;
}

/**
 * ice_cleanup_headers - Correct empty headers
 * @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 ice_cleanup_headers(struct sk_buff *skb)
{
        /* place header in linear portion of buffer */
        if (skb_is_nonlinear(skb))
                ice_pull_tail(skb);

        /* if eth_skb_pad returns an error the skb was freed */
        if (eth_skb_pad(skb))
                return true;

        return false;
}

/**
 * ice_test_staterr - tests bits in Rx descriptor status and error fields
 * @rx_desc: pointer to receive descriptor (in le64 format)
 * @stat_err_bits: value to mask
 *
 * This function does some fast chicanery in order to return the
 * value of the mask which is really only used for boolean tests.
 * The status_error_len doesn't need to be shifted because it begins
 * at offset zero.
 */
static bool ice_test_staterr(union ice_32b_rx_flex_desc *rx_desc,
                             const u16 stat_err_bits)
{
        return !!(rx_desc->wb.status_error0 &
                  cpu_to_le16(stat_err_bits));
}

/**
 * ice_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 ice_is_non_eop(struct ice_ring *rx_ring,
                           union ice_32b_rx_flex_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(ICE_RX_DESC(rx_ring, ntc));

        /* if we are the last buffer then there is nothing else to do */
#define ICE_RXD_EOF BIT(ICE_RX_FLEX_DESC_STATUS0_EOF_S)
        if (likely(ice_test_staterr(rx_desc, ICE_RXD_EOF)))
                return false;

        /* place skb in next buffer to be received */
        rx_ring->rx_buf[ntc].skb = skb;
        rx_ring->rx_stats.non_eop_descs++;

        return true;
}

/**
 * ice_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 enum pkt_hash_types ice_ptype_to_htype(u8 __always_unused ptype)
{
        return PKT_HASH_TYPE_NONE;
}

/**
 * ice_rx_hash - set the hash value in the skb
 * @rx_ring: descriptor ring
 * @rx_desc: specific descriptor
 * @skb: pointer to current skb
 * @rx_ptype: the ptype value from the descriptor
 */
static void
ice_rx_hash(struct ice_ring *rx_ring, union ice_32b_rx_flex_desc *rx_desc,
            struct sk_buff *skb, u8 rx_ptype)
{
        struct ice_32b_rx_flex_desc_nic *nic_mdid;
        u32 hash;

        if (!(rx_ring->netdev->features & NETIF_F_RXHASH))
                return;

        if (rx_desc->wb.rxdid != ICE_RXDID_FLEX_NIC)
                return;

        nic_mdid = (struct ice_32b_rx_flex_desc_nic *)rx_desc;
        hash = le32_to_cpu(nic_mdid->rss_hash);
        skb_set_hash(skb, hash, ice_ptype_to_htype(rx_ptype));
}

/**
 * ice_rx_csum - Indicate in skb if checksum is good
 * @vsi: the VSI we care about
 * @skb: skb currently being received and modified
 * @rx_desc: the receive descriptor
 * @ptype: the packet type decoded by hardware
 *
 * skb->protocol must be set before this function is called
 */
static void ice_rx_csum(struct ice_vsi *vsi, struct sk_buff *skb,
                        union ice_32b_rx_flex_desc *rx_desc, u8 ptype)
{
        struct ice_rx_ptype_decoded decoded;
        u32 rx_error, rx_status;
        bool ipv4, ipv6;

        rx_status = le16_to_cpu(rx_desc->wb.status_error0);
        rx_error = rx_status;

        decoded = ice_decode_rx_desc_ptype(ptype);

        /* Start with CHECKSUM_NONE and by default csum_level = 0 */
        skb->ip_summed = CHECKSUM_NONE;
        skb_checksum_none_assert(skb);

        /* check if Rx checksum is enabled */
        if (!(vsi->netdev->features & NETIF_F_RXCSUM))
                return;

        /* check if HW has decoded the packet and checksum */
        if (!(rx_status & BIT(ICE_RX_FLEX_DESC_STATUS0_L3L4P_S)))
                return;

        if (!(decoded.known && decoded.outer_ip))
                return;

        ipv4 = (decoded.outer_ip == ICE_RX_PTYPE_OUTER_IP) &&
               (decoded.outer_ip_ver == ICE_RX_PTYPE_OUTER_IPV4);
        ipv6 = (decoded.outer_ip == ICE_RX_PTYPE_OUTER_IP) &&
               (decoded.outer_ip_ver == ICE_RX_PTYPE_OUTER_IPV6);

        if (ipv4 && (rx_error & (BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_IPE_S) |
                                 BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_EIPE_S))))
                goto checksum_fail;
        else if (ipv6 && (rx_status &
                 (BIT(ICE_RX_FLEX_DESC_STATUS0_IPV6EXADD_S))))
                goto checksum_fail;

        /* check for L4 errors and handle packets that were not able to be
         * checksummed due to arrival speed
         */
        if (rx_error & BIT(ICE_RX_FLEX_DESC_STATUS0_XSUM_L4E_S))
                goto checksum_fail;

        /* Only report checksum unnecessary for TCP, UDP, or SCTP */
        switch (decoded.inner_prot) {
        case ICE_RX_PTYPE_INNER_PROT_TCP:
        case ICE_RX_PTYPE_INNER_PROT_UDP:
        case ICE_RX_PTYPE_INNER_PROT_SCTP:
                skb->ip_summed = CHECKSUM_UNNECESSARY;
        default:
                break;
        }
        return;

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

/**
 * ice_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
 * @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 void ice_process_skb_fields(struct ice_ring *rx_ring,
                                   union ice_32b_rx_flex_desc *rx_desc,
                                   struct sk_buff *skb, u8 ptype)
{
        ice_rx_hash(rx_ring, rx_desc, skb, ptype);

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

        ice_rx_csum(rx_ring->vsi, skb, rx_desc, ptype);
}

/**
 * ice_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
 *
 * This function sends the completed packet (via. skb) up the stack using
 * gro receive functions (with/without vlan tag)
 */
static void ice_receive_skb(struct ice_ring *rx_ring, struct sk_buff *skb,
                            u16 vlan_tag)
{
        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(&rx_ring->q_vector->napi, skb);
}

/**
 * ice_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 ice_clean_rx_irq(struct ice_ring *rx_ring, int budget)
{
        unsigned int total_rx_bytes = 0, total_rx_pkts = 0;
        u16 cleaned_count = ICE_DESC_UNUSED(rx_ring);
        bool failure = false;

        /* start the loop to process RX packets bounded by 'budget' */
        while (likely(total_rx_pkts < (unsigned int)budget)) {
                union ice_32b_rx_flex_desc *rx_desc;
                struct sk_buff *skb;
                u16 stat_err_bits;
                u16 vlan_tag = 0;
                u8 rx_ptype;

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

                /* get the RX desc from RX ring based on 'next_to_clean' */
                rx_desc = ICE_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 it will be non-zero
                 */
                stat_err_bits = BIT(ICE_RX_FLEX_DESC_STATUS0_DD_S);
                if (!ice_test_staterr(rx_desc, stat_err_bits))
                        break;

                /* This memory barrier is needed to keep us from reading
                 * any other fields out of the rx_desc until we know the
                 * DD bit is set.
                 */
                dma_rmb();

                /* allocate (if needed) and populate skb */
                skb = ice_fetch_rx_buf(rx_ring, rx_desc);
                if (!skb)
                        break;

                cleaned_count++;

                /* skip if it is NOP desc */
                if (ice_is_non_eop(rx_ring, rx_desc, skb))
                        continue;

                stat_err_bits = BIT(ICE_RX_FLEX_DESC_STATUS0_RXE_S);
                if (unlikely(ice_test_staterr(rx_desc, stat_err_bits))) {
                        dev_kfree_skb_any(skb);
                        continue;
                }

                rx_ptype = le16_to_cpu(rx_desc->wb.ptype_flex_flags0) &
                        ICE_RX_FLEX_DESC_PTYPE_M;

                stat_err_bits = BIT(ICE_RX_FLEX_DESC_STATUS0_L2TAG1P_S);
                if (ice_test_staterr(rx_desc, stat_err_bits))
                        vlan_tag = le16_to_cpu(rx_desc->wb.l2tag1);

                /* correct empty headers and pad skb if needed (to make valid
                 * ethernet frame
                 */
                if (ice_cleanup_headers(skb)) {
                        skb = NULL;
                        continue;
                }

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

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

                /* send completed skb up the stack */
                ice_receive_skb(rx_ring, skb, vlan_tag);

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

        /* update queue and vector specific stats */
        u64_stats_update_begin(&rx_ring->syncp);
        rx_ring->stats.pkts += total_rx_pkts;
        rx_ring->stats.bytes += total_rx_bytes;
        u64_stats_update_end(&rx_ring->syncp);
        rx_ring->q_vector->rx.total_pkts += total_rx_pkts;
        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_pkts;
}

/**
 * ice_buildreg_itr - build value for writing to the GLINT_DYN_CTL register
 * @itr_idx: interrupt throttling index
 * @reg_itr: interrupt throttling value adjusted based on ITR granularity
 */
static u32 ice_buildreg_itr(int itr_idx, u16 reg_itr)
{
        return GLINT_DYN_CTL_INTENA_M | GLINT_DYN_CTL_CLEARPBA_M |
                (itr_idx << GLINT_DYN_CTL_ITR_INDX_S) |
                (reg_itr << GLINT_DYN_CTL_INTERVAL_S);
}

/**
 * ice_update_ena_itr - Update ITR and re-enable MSIX interrupt
 * @vsi: the VSI associated with the q_vector
 * @q_vector: q_vector for which ITR is being updated and interrupt enabled
 */
static void
ice_update_ena_itr(struct ice_vsi *vsi, struct ice_q_vector *q_vector)
{
        struct ice_hw *hw = &vsi->back->hw;
        struct ice_ring_container *rc;
        u32 itr_val;

        /* This block of logic allows us to get away with only updating
         * one ITR value with each interrupt. The idea is to perform a
         * pseudo-lazy update with the following criteria.
         *
         * 1. Rx is given higher priority than Tx if both are in same state
         * 2. If we must reduce an ITR that is given highest priority.
         * 3. We then give priority to increasing ITR based on amount.
         */
        if (q_vector->rx.target_itr < q_vector->rx.current_itr) {
                rc = &q_vector->rx;
                /* Rx ITR needs to be reduced, this is highest priority */
                itr_val = ice_buildreg_itr(rc->itr_idx, rc->target_itr);
                rc->current_itr = rc->target_itr;
        } else if ((q_vector->tx.target_itr < q_vector->tx.current_itr) ||
                   ((q_vector->rx.target_itr - q_vector->rx.current_itr) <
                    (q_vector->tx.target_itr - q_vector->tx.current_itr))) {
                rc = &q_vector->tx;
                /* Tx ITR needs to be reduced, this is second priority
                 * Tx ITR needs to be increased more than Rx, fourth priority
                 */
                itr_val = ice_buildreg_itr(rc->itr_idx, rc->target_itr);
                rc->current_itr = rc->target_itr;
        } else if (q_vector->rx.current_itr != q_vector->rx.target_itr) {
                rc = &q_vector->rx;
                /* Rx ITR needs to be increased, third priority */
                itr_val = ice_buildreg_itr(rc->itr_idx, rc->target_itr);
                rc->current_itr = rc->target_itr;
        } else {
                /* Still have to re-enable the interrupts */
                itr_val = ice_buildreg_itr(ICE_ITR_NONE, 0);
        }

        if (!test_bit(__ICE_DOWN, vsi->state)) {
                int vector = vsi->hw_base_vector + q_vector->v_idx;

                wr32(hw, GLINT_DYN_CTL(vector), itr_val);
        }
}

/**
 * ice_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 ice_napi_poll(struct napi_struct *napi, int budget)
{
        struct ice_q_vector *q_vector =
                                container_of(napi, struct ice_q_vector, napi);
        struct ice_vsi *vsi = q_vector->vsi;
        struct ice_pf *pf = vsi->back;
        bool clean_complete = true;
        int budget_per_ring = 0;
        struct ice_ring *ring;
        int work_done = 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.
         */
        ice_for_each_ring(ring, q_vector->tx)
                if (!ice_clean_tx_irq(vsi, ring, budget))
                        clean_complete = false;

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

        /* 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.
         */
        if (q_vector->num_ring_rx)
                budget_per_ring = max(budget / q_vector->num_ring_rx, 1);

        ice_for_each_ring(ring, q_vector->rx) {
                int cleaned;

                cleaned = ice_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)
                return budget;

        /* Exit the polling mode, but don't re-enable interrupts if stack might
         * poll us due to busy-polling
         */
        if (likely(napi_complete_done(napi, work_done)))
                if (test_bit(ICE_FLAG_MSIX_ENA, pf->flags))
                        ice_update_ena_itr(vsi, q_vector);

        return min_t(int, work_done, budget - 1);
}

/* helper function for building cmd/type/offset */
static __le64
build_ctob(u64 td_cmd, u64 td_offset, unsigned int size, u64 td_tag)
{
        return cpu_to_le64(ICE_TX_DESC_DTYPE_DATA |
                           (td_cmd    << ICE_TXD_QW1_CMD_S) |
                           (td_offset << ICE_TXD_QW1_OFFSET_S) |
                           ((u64)size << ICE_TXD_QW1_TX_BUF_SZ_S) |
                           (td_tag    << ICE_TXD_QW1_L2TAG1_S));
}

/**
 * __ice_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
 */
static int __ice_maybe_stop_tx(struct ice_ring *tx_ring, unsigned int size)
{
        netif_stop_subqueue(tx_ring->netdev, tx_ring->q_index);
        /* Memory barrier before checking head and tail */
        smp_mb();

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

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

/**
 * ice_maybe_stop_tx - 1st level check for Tx stop conditions
 * @tx_ring: the ring to be checked
 * @size:    the size buffer we want to assure is available
 *
 * Returns 0 if stop is not needed
 */
static int ice_maybe_stop_tx(struct ice_ring *tx_ring, unsigned int size)
{
        if (likely(ICE_DESC_UNUSED(tx_ring) >= size))
                return 0;

        return __ice_maybe_stop_tx(tx_ring, size);
}

/**
 * ice_tx_map - Build the Tx descriptor
 * @tx_ring: ring to send buffer on
 * @first: first buffer info buffer to use
 * @off: pointer to struct that holds offload parameters
 *
 * This function loops over the skb data pointed to by *first
 * and gets a physical address for each memory location and programs
 * it and the length into the transmit descriptor.
 */
static void
ice_tx_map(struct ice_ring *tx_ring, struct ice_tx_buf *first,
           struct ice_tx_offload_params *off)
{
        u64 td_offset, td_tag, td_cmd;
        u16 i = tx_ring->next_to_use;
        struct skb_frag_struct *frag;
        unsigned int data_len, size;
        struct ice_tx_desc *tx_desc;
        struct ice_tx_buf *tx_buf;
        struct sk_buff *skb;
        dma_addr_t dma;

        td_tag = off->td_l2tag1;
        td_cmd = off->td_cmd;
        td_offset = off->td_offset;
        skb = first->skb;

        data_len = skb->data_len;
        size = skb_headlen(skb);

        tx_desc = ICE_TX_DESC(tx_ring, i);

        if (first->tx_flags & ICE_TX_FLAGS_HW_VLAN) {
                td_cmd |= (u64)ICE_TX_DESC_CMD_IL2TAG1;
                td_tag = (first->tx_flags & ICE_TX_FLAGS_VLAN_M) >>
                          ICE_TX_FLAGS_VLAN_S;
        }

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

        tx_buf = first;

        for (frag = &skb_shinfo(skb)->frags[0];; frag++) {
                unsigned int max_data = ICE_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_buf, len, size);
                dma_unmap_addr_set(tx_buf, dma, dma);

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

                /* account for data chunks larger than the hardware
                 * can handle
                 */
                while (unlikely(size > ICE_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 = ICE_TX_DESC(tx_ring, 0);
                                i = 0;
                        }

                        dma += max_data;
                        size -= max_data;

                        max_data = ICE_MAX_DATA_PER_TXD_ALIGNED;
                        tx_desc->buf_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 = ICE_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_buf = &tx_ring->tx_buf[i];
        }

        /* record bytecount for BQL */
        netdev_tx_sent_queue(txring_txq(tx_ring), first->bytecount);

        /* record SW timestamp if HW timestamp is not available */
        skb_tx_timestamp(first->skb);

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

        /* write last descriptor with RS and EOP bits */
        td_cmd |= (u64)(ICE_TX_DESC_CMD_EOP | ICE_TX_DESC_CMD_RS);
        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;

        tx_ring->next_to_use = i;

        ice_maybe_stop_tx(tx_ring, DESC_NEEDED);

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

        return;

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

        tx_ring->next_to_use = i;
}

/**
 * ice_tx_csum - Enable Tx checksum offloads
 * @first: pointer to the first descriptor
 * @off: pointer to struct that holds offload parameters
 *
 * Returns 0 or error (negative) if checksum offload can't happen, 1 otherwise.
 */
static
int ice_tx_csum(struct ice_tx_buf *first, struct ice_tx_offload_params *off)
{
        u32 l4_len = 0, l3_len = 0, l2_len = 0;
        struct sk_buff *skb = first->skb;
        union {
                struct iphdr *v4;
                struct ipv6hdr *v6;
                unsigned char *hdr;
        } ip;
        union {
                struct tcphdr *tcp;
                unsigned char *hdr;
        } l4;
        __be16 frag_off, protocol;
        unsigned char *exthdr;
        u32 offset, cmd = 0;
        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 */
        l2_len = ip.hdr - skb->data;
        offset = (l2_len / 2) << ICE_TX_DESC_LEN_MACLEN_S;

        if (skb->encapsulation)
                return -1;

        /* Enable IP checksum offloads */
        protocol = vlan_get_protocol(skb);
        if (protocol == htons(ETH_P_IP)) {
                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.
                 */
                if (first->tx_flags & ICE_TX_FLAGS_TSO)
                        cmd |= ICE_TX_DESC_CMD_IIPT_IPV4_CSUM;
                else
                        cmd |= ICE_TX_DESC_CMD_IIPT_IPV4;

        } else if (protocol == htons(ETH_P_IPV6)) {
                cmd |= ICE_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);
        } else {
                return -1;
        }

        /* compute inner L3 header size */
        l3_len = l4.hdr - ip.hdr;
        offset |= (l3_len / 4) << ICE_TX_DESC_LEN_IPLEN_S;

        /* Enable L4 checksum offloads */
        switch (l4_proto) {
        case IPPROTO_TCP:
                /* enable checksum offloads */
                cmd |= ICE_TX_DESC_CMD_L4T_EOFT_TCP;
                l4_len = l4.tcp->doff;
                offset |= l4_len << ICE_TX_DESC_LEN_L4_LEN_S;
                break;
        case IPPROTO_UDP:
                /* enable UDP checksum offload */
                cmd |= ICE_TX_DESC_CMD_L4T_EOFT_UDP;
                l4_len = (sizeof(struct udphdr) >> 2);
                offset |= l4_len << ICE_TX_DESC_LEN_L4_LEN_S;
                break;
        case IPPROTO_SCTP:
                /* enable SCTP checksum offload */
                cmd |= ICE_TX_DESC_CMD_L4T_EOFT_SCTP;
                l4_len = sizeof(struct sctphdr) >> 2;
                offset |= l4_len << ICE_TX_DESC_LEN_L4_LEN_S;
                break;

        default:
                if (first->tx_flags & ICE_TX_FLAGS_TSO)
                        return -1;
                skb_checksum_help(skb);
                return 0;
        }

        off->td_cmd |= cmd;
        off->td_offset |= offset;
        return 1;
}

/**
 * ice_tx_prepare_vlan_flags - prepare generic TX VLAN tagging flags for HW
 * @tx_ring: ring to send buffer on
 * @first: pointer to struct ice_tx_buf
 *
 * 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 int
ice_tx_prepare_vlan_flags(struct ice_ring *tx_ring, struct ice_tx_buf *first)
{
        struct sk_buff *skb = first->skb;
        __be16 protocol = skb->protocol;

        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)) {
                first->tx_flags |= skb_vlan_tag_get(skb) << ICE_TX_FLAGS_VLAN_S;
                first->tx_flags |= ICE_TX_FLAGS_HW_VLAN;
        } else if (protocol == htons(ETH_P_8021Q)) {
                struct vlan_hdr *vhdr, _vhdr;

                /* for SW VLAN, check the next protocol and store the tag */
                vhdr = (struct vlan_hdr *)skb_header_pointer(skb, ETH_HLEN,
                                                             sizeof(_vhdr),
                                                             &_vhdr);
                if (!vhdr)
                        return -EINVAL;

                first->tx_flags |= ntohs(vhdr->h_vlan_TCI) <<
                                   ICE_TX_FLAGS_VLAN_S;
                first->tx_flags |= ICE_TX_FLAGS_SW_VLAN;
        }

out:
        return 0;
}

/**
 * ice_tso - computes mss and TSO length to prepare for TSO
 * @first: pointer to struct ice_tx_buf
 * @off: pointer to struct that holds offload parameters
 *
 * Returns 0 or error (negative) if TSO can't happen, 1 otherwise.
 */
static
int ice_tso(struct ice_tx_buf *first, struct ice_tx_offload_params *off)
{
        struct sk_buff *skb = first->skb;
        union {
                struct iphdr *v4;
                struct ipv6hdr *v6;
                unsigned char *hdr;
        } ip;
        union {
                struct tcphdr *tcp;
                unsigned char *hdr;
        } l4;
        u64 cd_mss, cd_tso_len;
        u32 paylen, l4_start;
        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;
        }

        /* determine offset of transport header */
        l4_start = l4.hdr - skb->data;

        /* remove payload length from checksum */
        paylen = skb->len - l4_start;
        csum_replace_by_diff(&l4.tcp->check, (__force __wsum)htonl(paylen));

        /* compute length of segmentation header */
        off->header_len = (l4.tcp->doff * 4) + l4_start;

        /* update gso_segs and bytecount */
        first->gso_segs = skb_shinfo(skb)->gso_segs;
        first->bytecount += (first->gso_segs - 1) * off->header_len;

        cd_tso_len = skb->len - off->header_len;
        cd_mss = skb_shinfo(skb)->gso_size;

        /* record cdesc_qw1 with TSO parameters */
        off->cd_qw1 |= ICE_TX_DESC_DTYPE_CTX |
                         (ICE_TX_CTX_DESC_TSO << ICE_TXD_CTX_QW1_CMD_S) |
                         (cd_tso_len << ICE_TXD_CTX_QW1_TSO_LEN_S) |
                         (cd_mss << ICE_TXD_CTX_QW1_MSS_S);
        first->tx_flags |= ICE_TX_FLAGS_TSO;
        return 1;
}

/**
 * ice_txd_use_count  - estimate the number of descriptors needed for Tx
 * @size: transmit request size in bytes
 *
 * Due to hardware alignment restrictions (4K alignment), we need to
 * assume that we can have no more than 12K of data per descriptor, even
 * though each descriptor can take up to 16K - 1 bytes of aligned memory.
 * Thus, we need to divide by 12K. But division is slow! Instead,
 * we decompose the operation into shifts and one relatively cheap
 * multiply operation.
 *
 * To divide by 12K, we first divide by 4K, then divide by 3:
 *     To divide by 4K, shift right by 12 bits
 *     To divide by 3, multiply by 85, then divide by 256
 *     (Divide by 256 is done by shifting right by 8 bits)
 * Finally, we add one to round up. Because 256 isn't an exact multiple of
 * 3, we'll underestimate near each multiple of 12K. This is actually more
 * accurate as we have 4K - 1 of wiggle room that we can fit into the last
 * segment. For our purposes this is accurate out to 1M which is orders of
 * magnitude greater than our largest possible GSO size.
 *
 * This would then be implemented as:
 *     return (((size >> 12) * 85) >> 8) + ICE_DESCS_FOR_SKB_DATA_PTR;
 *
 * Since multiplication and division are commutative, we can reorder
 * operations into:
 *     return ((size * 85) >> 20) + ICE_DESCS_FOR_SKB_DATA_PTR;
 */
static unsigned int ice_txd_use_count(unsigned int size)
{
        return ((size * 85) >> 20) + ICE_DESCS_FOR_SKB_DATA_PTR;
}

/**
 * ice_xmit_desc_count - calculate number of Tx descriptors needed
 * @skb: send buffer
 *
 * Returns number of data descriptors needed for this skb.
 */
static unsigned int ice_xmit_desc_count(struct sk_buff *skb)
{
        const struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[0];
        unsigned int nr_frags = skb_shinfo(skb)->nr_frags;
        unsigned int count = 0, size = skb_headlen(skb);

        for (;;) {
                count += ice_txd_use_count(size);

                if (!nr_frags--)
                        break;

                size = skb_frag_size(frag++);
        }

        return count;
}

/**
 * __ice_chk_linearize - Check if there are more than 8 buffers per packet
 * @skb: send buffer
 *
 * Note: This 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.
 */
static bool __ice_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 < (ICE_MAX_BUF_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 -= ICE_MAX_BUF_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.
         */
        stale = &skb_shinfo(skb)->frags[0];
        for (;;) {
                sum += skb_frag_size(frag++);

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

                if (!nr_frags--)
                        break;

                sum -= skb_frag_size(stale++);
        }

        return false;
}

/**
 * ice_chk_linearize - Check if there are more than 8 fragments per packet
 * @skb:      send buffer
 * @count:    number of buffers used
 *
 * Note: Our HW can't scatter-gather more than 8 fragments to build
 * a packet on the wire and so we need to figure out the cases where we
 * need to linearize the skb.
 */
static bool ice_chk_linearize(struct sk_buff *skb, unsigned int count)
{
        /* Both TSO and single send will work if count is less than 8 */
        if (likely(count < ICE_MAX_BUF_TXD))
                return false;

        if (skb_is_gso(skb))
                return __ice_chk_linearize(skb);

        /* we can support up to 8 data buffers for a single send */
        return count != ICE_MAX_BUF_TXD;
}

/**
 * ice_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
ice_xmit_frame_ring(struct sk_buff *skb, struct ice_ring *tx_ring)
{
        struct ice_tx_offload_params offload = { 0 };
        struct ice_tx_buf *first;
        unsigned int count;
        int tso, csum;

        count = ice_xmit_desc_count(skb);
        if (ice_chk_linearize(skb, count)) {
                if (__skb_linearize(skb))
                        goto out_drop;
                count = ice_txd_use_count(skb->len);
                tx_ring->tx_stats.tx_linearize++;
        }

        /* need: 1 descriptor per page * PAGE_SIZE/ICE_MAX_DATA_PER_TXD,
         *       + 1 desc for skb_head_len/ICE_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 (ice_maybe_stop_tx(tx_ring, count + ICE_DESCS_PER_CACHE_LINE +
                              ICE_DESCS_FOR_CTX_DESC)) {
                tx_ring->tx_stats.tx_busy++;
                return NETDEV_TX_BUSY;
        }

        offload.tx_ring = tx_ring;

        /* record the location of the first descriptor for this packet */
        first = &tx_ring->tx_buf[tx_ring->next_to_use];
        first->skb = skb;
        first->bytecount = max_t(unsigned int, skb->len, ETH_ZLEN);
        first->gso_segs = 1;
        first->tx_flags = 0;

        /* prepare the VLAN tagging flags for Tx */
        if (ice_tx_prepare_vlan_flags(tx_ring, first))
                goto out_drop;

        /* set up TSO offload */
        tso = ice_tso(first, &offload);
        if (tso < 0)
                goto out_drop;

        /* always set up Tx checksum offload */
        csum = ice_tx_csum(first, &offload);
        if (csum < 0)
                goto out_drop;

        if (tso || offload.cd_tunnel_params) {
                struct ice_tx_ctx_desc *cdesc;
                int i = tx_ring->next_to_use;

                /* grab the next descriptor */
                cdesc = ICE_TX_CTX_DESC(tx_ring, i);
                i++;
                tx_ring->next_to_use = (i < tx_ring->count) ? i : 0;

                /* setup context descriptor */
                cdesc->tunneling_params = cpu_to_le32(offload.cd_tunnel_params);
                cdesc->l2tag2 = cpu_to_le16(offload.cd_l2tag2);
                cdesc->rsvd = cpu_to_le16(0);
                cdesc->qw1 = cpu_to_le64(offload.cd_qw1);
        }

        ice_tx_map(tx_ring, first, &offload);
        return NETDEV_TX_OK;

out_drop:
        dev_kfree_skb_any(skb);
        return NETDEV_TX_OK;
}

/**
 * ice_start_xmit - 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 ice_start_xmit(struct sk_buff *skb, struct net_device *netdev)
{
        struct ice_netdev_priv *np = netdev_priv(netdev);
        struct ice_vsi *vsi = np->vsi;
        struct ice_ring *tx_ring;

        tx_ring = vsi->tx_rings[skb->queue_mapping];

        /* hardware can't handle really short frames, hardware padding works
         * beyond this point
         */
        if (skb_put_padto(skb, ICE_MIN_TX_LEN))
                return NETDEV_TX_OK;

        return ice_xmit_frame_ring(skb, tx_ring);
}