[mirror_ubuntu-artful-kernel.git] / drivers / net / ethernet / sfc / rx.c

/****************************************************************************
 * Driver for Solarflare Solarstorm network controllers and boards
 * Copyright 2005-2006 Fen Systems Ltd.
 * Copyright 2005-2011 Solarflare Communications Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation, incorporated herein by reference.
 */

#include <linux/socket.h>
#include <linux/in.h>
#include <linux/slab.h>
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/prefetch.h>
#include <linux/moduleparam.h>
#include <net/ip.h>
#include <net/checksum.h>
#include "net_driver.h"
#include "efx.h"
#include "nic.h"
#include "selftest.h"
#include "workarounds.h"

/* Number of RX descriptors pushed at once. */
#define EFX_RX_BATCH  8

/* Maximum size of a buffer sharing a page */
#define EFX_RX_HALF_PAGE ((PAGE_SIZE >> 1) - sizeof(struct efx_rx_page_state))

/* Size of buffer allocated for skb header area. */
#define EFX_SKB_HEADERS  64u

/*
 * rx_alloc_method - RX buffer allocation method
 *
 * This driver supports two methods for allocating and using RX buffers:
 * each RX buffer may be backed by an skb or by an order-n page.
 *
 * When GRO is in use then the second method has a lower overhead,
 * since we don't have to allocate then free skbs on reassembled frames.
 *
 * Values:
 *   - RX_ALLOC_METHOD_AUTO = 0
 *   - RX_ALLOC_METHOD_SKB  = 1
 *   - RX_ALLOC_METHOD_PAGE = 2
 *
 * The heuristic for %RX_ALLOC_METHOD_AUTO is a simple hysteresis count
 * controlled by the parameters below.
 *
 *   - Since pushing and popping descriptors are separated by the rx_queue
 *     size, so the watermarks should be ~rxd_size.
 *   - The performance win by using page-based allocation for GRO is less
 *     than the performance hit of using page-based allocation of non-GRO,
 *     so the watermarks should reflect this.
 *
 * Per channel we maintain a single variable, updated by each channel:
 *
 *   rx_alloc_level += (gro_performed ? RX_ALLOC_FACTOR_GRO :
 *                      RX_ALLOC_FACTOR_SKB)
 * Per NAPI poll interval, we constrain rx_alloc_level to 0..MAX (which
 * limits the hysteresis), and update the allocation strategy:
 *
 *   rx_alloc_method = (rx_alloc_level > RX_ALLOC_LEVEL_GRO ?
 *                      RX_ALLOC_METHOD_PAGE : RX_ALLOC_METHOD_SKB)
 */
static int rx_alloc_method = RX_ALLOC_METHOD_AUTO;

#define RX_ALLOC_LEVEL_GRO 0x2000
#define RX_ALLOC_LEVEL_MAX 0x3000
#define RX_ALLOC_FACTOR_GRO 1
#define RX_ALLOC_FACTOR_SKB (-2)

/* This is the percentage fill level below which new RX descriptors
 * will be added to the RX descriptor ring.
 */
static unsigned int rx_refill_threshold;

/*
 * RX maximum head room required.
 *
 * This must be at least 1 to prevent overflow and at least 2 to allow
 * pipelined receives.
 */
#define EFX_RXD_HEAD_ROOM 2

/* Offset of ethernet header within page */
static inline unsigned int efx_rx_buf_offset(struct efx_nic *efx,
                                             struct efx_rx_buffer *buf)
{
        return buf->page_offset + efx->type->rx_buffer_hash_size;
}
static inline unsigned int efx_rx_buf_size(struct efx_nic *efx)
{
        return PAGE_SIZE << efx->rx_buffer_order;
}

static u8 *efx_rx_buf_eh(struct efx_nic *efx, struct efx_rx_buffer *buf)
{
        if (buf->flags & EFX_RX_BUF_PAGE)
                return page_address(buf->u.page) + efx_rx_buf_offset(efx, buf);
        else
                return (u8 *)buf->u.skb->data + efx->type->rx_buffer_hash_size;
}

static inline u32 efx_rx_buf_hash(const u8 *eh)
{
        /* The ethernet header is always directly after any hash. */
#if defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) || NET_IP_ALIGN % 4 == 0
        return __le32_to_cpup((const __le32 *)(eh - 4));
#else
        const u8 *data = eh - 4;
        return (u32)data[0]       |
               (u32)data[1] << 8  |
               (u32)data[2] << 16 |
               (u32)data[3] << 24;
#endif
}

/**
 * efx_init_rx_buffers_skb - create EFX_RX_BATCH skb-based RX buffers
 *
 * @rx_queue:           Efx RX queue
 *
 * This allocates EFX_RX_BATCH skbs, maps them for DMA, and populates a
 * struct efx_rx_buffer for each one. Return a negative error code or 0
 * on success. May fail having only inserted fewer than EFX_RX_BATCH
 * buffers.
 */
static int efx_init_rx_buffers_skb(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        struct net_device *net_dev = efx->net_dev;
        struct efx_rx_buffer *rx_buf;
        struct sk_buff *skb;
        int skb_len = efx->rx_buffer_len;
        unsigned index, count;

        for (count = 0; count < EFX_RX_BATCH; ++count) {
                index = rx_queue->added_count & rx_queue->ptr_mask;
                rx_buf = efx_rx_buffer(rx_queue, index);

                rx_buf->u.skb = skb = netdev_alloc_skb(net_dev, skb_len);
                if (unlikely(!skb))
                        return -ENOMEM;

                /* Adjust the SKB for padding */
                skb_reserve(skb, NET_IP_ALIGN);
                rx_buf->len = skb_len - NET_IP_ALIGN;
                rx_buf->flags = 0;

                rx_buf->dma_addr = dma_map_single(&efx->pci_dev->dev,
                                                  skb->data, rx_buf->len,
                                                  DMA_FROM_DEVICE);
                if (unlikely(dma_mapping_error(&efx->pci_dev->dev,
                                               rx_buf->dma_addr))) {
                        dev_kfree_skb_any(skb);
                        rx_buf->u.skb = NULL;
                        return -EIO;
                }

                ++rx_queue->added_count;
                ++rx_queue->alloc_skb_count;
        }

        return 0;
}

/**
 * efx_init_rx_buffers_page - create EFX_RX_BATCH page-based RX buffers
 *
 * @rx_queue:           Efx RX queue
 *
 * This allocates memory for EFX_RX_BATCH receive buffers, maps them for DMA,
 * and populates struct efx_rx_buffers for each one. Return a negative error
 * code or 0 on success. If a single page can be split between two buffers,
 * then the page will either be inserted fully, or not at at all.
 */
static int efx_init_rx_buffers_page(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        struct efx_rx_buffer *rx_buf;
        struct page *page;
        unsigned int page_offset;
        struct efx_rx_page_state *state;
        dma_addr_t dma_addr;
        unsigned index, count;

        /* We can split a page between two buffers */
        BUILD_BUG_ON(EFX_RX_BATCH & 1);

        for (count = 0; count < EFX_RX_BATCH; ++count) {
                page = alloc_pages(__GFP_COLD | __GFP_COMP | GFP_ATOMIC,
                                   efx->rx_buffer_order);
                if (unlikely(page == NULL))
                        return -ENOMEM;
                dma_addr = dma_map_page(&efx->pci_dev->dev, page, 0,
                                        efx_rx_buf_size(efx),
                                        DMA_FROM_DEVICE);
                if (unlikely(dma_mapping_error(&efx->pci_dev->dev, dma_addr))) {
                        __free_pages(page, efx->rx_buffer_order);
                        return -EIO;
                }
                state = page_address(page);
                state->refcnt = 0;
                state->dma_addr = dma_addr;

                dma_addr += sizeof(struct efx_rx_page_state);
                page_offset = sizeof(struct efx_rx_page_state);

        split:
                index = rx_queue->added_count & rx_queue->ptr_mask;
                rx_buf = efx_rx_buffer(rx_queue, index);
                rx_buf->dma_addr = dma_addr + EFX_PAGE_IP_ALIGN;
                rx_buf->u.page = page;
                rx_buf->page_offset = page_offset;
                rx_buf->len = efx->rx_buffer_len - EFX_PAGE_IP_ALIGN;
                rx_buf->flags = EFX_RX_BUF_PAGE;
                ++rx_queue->added_count;
                ++rx_queue->alloc_page_count;
                ++state->refcnt;

                if ((~count & 1) && (efx->rx_buffer_len <= EFX_RX_HALF_PAGE)) {
                        /* Use the second half of the page */
                        get_page(page);
                        dma_addr += (PAGE_SIZE >> 1);
                        page_offset += (PAGE_SIZE >> 1);
                        ++count;
                        goto split;
                }
        }

        return 0;
}

static void efx_unmap_rx_buffer(struct efx_nic *efx,
                                struct efx_rx_buffer *rx_buf,
                                unsigned int used_len)
{
        if ((rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.page) {
                struct efx_rx_page_state *state;

                state = page_address(rx_buf->u.page);
                if (--state->refcnt == 0) {
                        dma_unmap_page(&efx->pci_dev->dev,
                                       state->dma_addr,
                                       efx_rx_buf_size(efx),
                                       DMA_FROM_DEVICE);
                } else if (used_len) {
                        dma_sync_single_for_cpu(&efx->pci_dev->dev,
                                                rx_buf->dma_addr, used_len,
                                                DMA_FROM_DEVICE);
                }
        } else if (!(rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.skb) {
                dma_unmap_single(&efx->pci_dev->dev, rx_buf->dma_addr,
                                 rx_buf->len, DMA_FROM_DEVICE);
        }
}

static void efx_free_rx_buffer(struct efx_nic *efx,
                               struct efx_rx_buffer *rx_buf)
{
        if ((rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.page) {
                __free_pages(rx_buf->u.page, efx->rx_buffer_order);
                rx_buf->u.page = NULL;
        } else if (!(rx_buf->flags & EFX_RX_BUF_PAGE) && rx_buf->u.skb) {
                dev_kfree_skb_any(rx_buf->u.skb);
                rx_buf->u.skb = NULL;
        }
}

static void efx_fini_rx_buffer(struct efx_rx_queue *rx_queue,
                               struct efx_rx_buffer *rx_buf)
{
        efx_unmap_rx_buffer(rx_queue->efx, rx_buf, 0);
        efx_free_rx_buffer(rx_queue->efx, rx_buf);
}

/* Attempt to resurrect the other receive buffer that used to share this page,
 * which had previously been passed up to the kernel and freed. */
static void efx_resurrect_rx_buffer(struct efx_rx_queue *rx_queue,
                                    struct efx_rx_buffer *rx_buf)
{
        struct efx_rx_page_state *state = page_address(rx_buf->u.page);
        struct efx_rx_buffer *new_buf;
        unsigned fill_level, index;

        /* +1 because efx_rx_packet() incremented removed_count. +1 because
         * we'd like to insert an additional descriptor whilst leaving
         * EFX_RXD_HEAD_ROOM for the non-recycle path */
        fill_level = (rx_queue->added_count - rx_queue->removed_count + 2);
        if (unlikely(fill_level > rx_queue->max_fill)) {
                /* We could place "state" on a list, and drain the list in
                 * efx_fast_push_rx_descriptors(). For now, this will do. */
                return;
        }

        ++state->refcnt;
        get_page(rx_buf->u.page);

        index = rx_queue->added_count & rx_queue->ptr_mask;
        new_buf = efx_rx_buffer(rx_queue, index);
        new_buf->dma_addr = rx_buf->dma_addr ^ (PAGE_SIZE >> 1);
        new_buf->u.page = rx_buf->u.page;
        new_buf->len = rx_buf->len;
        new_buf->flags = EFX_RX_BUF_PAGE;
        ++rx_queue->added_count;
}

/* Recycle the given rx buffer directly back into the rx_queue. There is
 * always room to add this buffer, because we've just popped a buffer. */
static void efx_recycle_rx_buffer(struct efx_channel *channel,
                                  struct efx_rx_buffer *rx_buf)
{
        struct efx_nic *efx = channel->efx;
        struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);
        struct efx_rx_buffer *new_buf;
        unsigned index;

        rx_buf->flags &= EFX_RX_BUF_PAGE;

        if ((rx_buf->flags & EFX_RX_BUF_PAGE) &&
            efx->rx_buffer_len <= EFX_RX_HALF_PAGE &&
            page_count(rx_buf->u.page) == 1)
                efx_resurrect_rx_buffer(rx_queue, rx_buf);

        index = rx_queue->added_count & rx_queue->ptr_mask;
        new_buf = efx_rx_buffer(rx_queue, index);

        memcpy(new_buf, rx_buf, sizeof(*new_buf));
        rx_buf->u.page = NULL;
        ++rx_queue->added_count;
}

/**
 * efx_fast_push_rx_descriptors - push new RX descriptors quickly
 * @rx_queue:           RX descriptor queue
 *
 * This will aim to fill the RX descriptor queue up to
 * @rx_queue->@max_fill. If there is insufficient atomic
 * memory to do so, a slow fill will be scheduled.
 *
 * The caller must provide serialisation (none is used here). In practise,
 * this means this function must run from the NAPI handler, or be called
 * when NAPI is disabled.
 */
void efx_fast_push_rx_descriptors(struct efx_rx_queue *rx_queue)
{
        struct efx_channel *channel = efx_rx_queue_channel(rx_queue);
        unsigned fill_level;
        int space, rc = 0;

        /* Calculate current fill level, and exit if we don't need to fill */
        fill_level = (rx_queue->added_count - rx_queue->removed_count);
        EFX_BUG_ON_PARANOID(fill_level > rx_queue->efx->rxq_entries);
        if (fill_level >= rx_queue->fast_fill_trigger)
                goto out;

        /* Record minimum fill level */
        if (unlikely(fill_level < rx_queue->min_fill)) {
                if (fill_level)
                        rx_queue->min_fill = fill_level;
        }

        space = rx_queue->max_fill - fill_level;
        EFX_BUG_ON_PARANOID(space < EFX_RX_BATCH);

        netif_vdbg(rx_queue->efx, rx_status, rx_queue->efx->net_dev,
                   "RX queue %d fast-filling descriptor ring from"
                   " level %d to level %d using %s allocation\n",
                   efx_rx_queue_index(rx_queue), fill_level,
                   rx_queue->max_fill,
                   channel->rx_alloc_push_pages ? "page" : "skb");

        do {
                if (channel->rx_alloc_push_pages)
                        rc = efx_init_rx_buffers_page(rx_queue);
                else
                        rc = efx_init_rx_buffers_skb(rx_queue);
                if (unlikely(rc)) {
                        /* Ensure that we don't leave the rx queue empty */
                        if (rx_queue->added_count == rx_queue->removed_count)
                                efx_schedule_slow_fill(rx_queue);
                        goto out;
                }
        } while ((space -= EFX_RX_BATCH) >= EFX_RX_BATCH);

        netif_vdbg(rx_queue->efx, rx_status, rx_queue->efx->net_dev,
                   "RX queue %d fast-filled descriptor ring "
                   "to level %d\n", efx_rx_queue_index(rx_queue),
                   rx_queue->added_count - rx_queue->removed_count);

 out:
        if (rx_queue->notified_count != rx_queue->added_count)
                efx_nic_notify_rx_desc(rx_queue);
}

void efx_rx_slow_fill(unsigned long context)
{
        struct efx_rx_queue *rx_queue = (struct efx_rx_queue *)context;

        /* Post an event to cause NAPI to run and refill the queue */
        efx_nic_generate_fill_event(rx_queue);
        ++rx_queue->slow_fill_count;
}

static void efx_rx_packet__check_len(struct efx_rx_queue *rx_queue,
                                     struct efx_rx_buffer *rx_buf,
                                     int len, bool *leak_packet)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned max_len = rx_buf->len - efx->type->rx_buffer_padding;

        if (likely(len <= max_len))
                return;

        /* The packet must be discarded, but this is only a fatal error
         * if the caller indicated it was
         */
        rx_buf->flags |= EFX_RX_PKT_DISCARD;

        if ((len > rx_buf->len) && EFX_WORKAROUND_8071(efx)) {
                if (net_ratelimit())
                        netif_err(efx, rx_err, efx->net_dev,
                                  " RX queue %d seriously overlength "
                                  "RX event (0x%x > 0x%x+0x%x). Leaking\n",
                                  efx_rx_queue_index(rx_queue), len, max_len,
                                  efx->type->rx_buffer_padding);
                /* If this buffer was skb-allocated, then the meta
                 * data at the end of the skb will be trashed. So
                 * we have no choice but to leak the fragment.
                 */
                *leak_packet = !(rx_buf->flags & EFX_RX_BUF_PAGE);
                efx_schedule_reset(efx, RESET_TYPE_RX_RECOVERY);
        } else {
                if (net_ratelimit())
                        netif_err(efx, rx_err, efx->net_dev,
                                  " RX queue %d overlength RX event "
                                  "(0x%x > 0x%x)\n",
                                  efx_rx_queue_index(rx_queue), len, max_len);
        }

        efx_rx_queue_channel(rx_queue)->n_rx_overlength++;
}

/* Pass a received packet up through GRO.  GRO can handle pages
 * regardless of checksum state and skbs with a good checksum.
 */
static void efx_rx_packet_gro(struct efx_channel *channel,
                              struct efx_rx_buffer *rx_buf,
                              const u8 *eh)
{
        struct napi_struct *napi = &channel->napi_str;
        gro_result_t gro_result;

        if (rx_buf->flags & EFX_RX_BUF_PAGE) {
                struct efx_nic *efx = channel->efx;
                struct page *page = rx_buf->u.page;
                struct sk_buff *skb;

                rx_buf->u.page = NULL;

                skb = napi_get_frags(napi);
                if (!skb) {
                        put_page(page);
                        return;
                }

                if (efx->net_dev->features & NETIF_F_RXHASH)
                        skb->rxhash = efx_rx_buf_hash(eh);

                skb_fill_page_desc(skb, 0, page,
                                   efx_rx_buf_offset(efx, rx_buf), rx_buf->len);

                skb->len = rx_buf->len;
                skb->data_len = rx_buf->len;
                skb->truesize += rx_buf->len;
                skb->ip_summed = ((rx_buf->flags & EFX_RX_PKT_CSUMMED) ?
                                  CHECKSUM_UNNECESSARY : CHECKSUM_NONE);

                skb_record_rx_queue(skb, channel->rx_queue.core_index);

                gro_result = napi_gro_frags(napi);
        } else {
                struct sk_buff *skb = rx_buf->u.skb;

                EFX_BUG_ON_PARANOID(!(rx_buf->flags & EFX_RX_PKT_CSUMMED));
                rx_buf->u.skb = NULL;
                skb->ip_summed = CHECKSUM_UNNECESSARY;

                gro_result = napi_gro_receive(napi, skb);
        }

        if (gro_result == GRO_NORMAL) {
                channel->rx_alloc_level += RX_ALLOC_FACTOR_SKB;
        } else if (gro_result != GRO_DROP) {
                channel->rx_alloc_level += RX_ALLOC_FACTOR_GRO;
                channel->irq_mod_score += 2;
        }
}

void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
                   unsigned int len, u16 flags)
{
        struct efx_nic *efx = rx_queue->efx;
        struct efx_channel *channel = efx_rx_queue_channel(rx_queue);
        struct efx_rx_buffer *rx_buf;
        bool leak_packet = false;

        rx_buf = efx_rx_buffer(rx_queue, index);
        rx_buf->flags |= flags;

        /* This allows the refill path to post another buffer.
         * EFX_RXD_HEAD_ROOM ensures that the slot we are using
         * isn't overwritten yet.
         */
        rx_queue->removed_count++;

        /* Validate the length encoded in the event vs the descriptor pushed */
        efx_rx_packet__check_len(rx_queue, rx_buf, len, &leak_packet);

        netif_vdbg(efx, rx_status, efx->net_dev,
                   "RX queue %d received id %x at %llx+%x %s%s\n",
                   efx_rx_queue_index(rx_queue), index,
                   (unsigned long long)rx_buf->dma_addr, len,
                   (rx_buf->flags & EFX_RX_PKT_CSUMMED) ? " [SUMMED]" : "",
                   (rx_buf->flags & EFX_RX_PKT_DISCARD) ? " [DISCARD]" : "");

        /* Discard packet, if instructed to do so */
        if (unlikely(rx_buf->flags & EFX_RX_PKT_DISCARD)) {
                if (unlikely(leak_packet))
                        channel->n_skbuff_leaks++;
                else
                        efx_recycle_rx_buffer(channel, rx_buf);

                /* Don't hold off the previous receive */
                rx_buf = NULL;
                goto out;
        }

        /* Release and/or sync DMA mapping - assumes all RX buffers
         * consumed in-order per RX queue
         */
        efx_unmap_rx_buffer(efx, rx_buf, len);

        /* Prefetch nice and early so data will (hopefully) be in cache by
         * the time we look at it.
         */
        prefetch(efx_rx_buf_eh(efx, rx_buf));

        /* Pipeline receives so that we give time for packet headers to be
         * prefetched into cache.
         */
        rx_buf->len = len - efx->type->rx_buffer_hash_size;
out:
        if (channel->rx_pkt)
                __efx_rx_packet(channel, channel->rx_pkt);
        channel->rx_pkt = rx_buf;
}

static void efx_rx_deliver(struct efx_channel *channel,
                           struct efx_rx_buffer *rx_buf)
{
        struct sk_buff *skb;

        /* We now own the SKB */
        skb = rx_buf->u.skb;
        rx_buf->u.skb = NULL;

        /* Set the SKB flags */
        skb_checksum_none_assert(skb);

        /* Record the rx_queue */
        skb_record_rx_queue(skb, channel->rx_queue.core_index);

        /* Pass the packet up */
        if (channel->type->receive_skb)
                channel->type->receive_skb(channel, skb);
        else
                netif_receive_skb(skb);

        /* Update allocation strategy method */
        channel->rx_alloc_level += RX_ALLOC_FACTOR_SKB;
}

/* Handle a received packet.  Second half: Touches packet payload. */
void __efx_rx_packet(struct efx_channel *channel, struct efx_rx_buffer *rx_buf)
{
        struct efx_nic *efx = channel->efx;
        u8 *eh = efx_rx_buf_eh(efx, rx_buf);

        /* If we're in loopback test, then pass the packet directly to the
         * loopback layer, and free the rx_buf here
         */
        if (unlikely(efx->loopback_selftest)) {
                efx_loopback_rx_packet(efx, eh, rx_buf->len);
                efx_free_rx_buffer(efx, rx_buf);
                return;
        }

        if (!(rx_buf->flags & EFX_RX_BUF_PAGE)) {
                struct sk_buff *skb = rx_buf->u.skb;

                prefetch(skb_shinfo(skb));

                skb_reserve(skb, efx->type->rx_buffer_hash_size);
                skb_put(skb, rx_buf->len);

                if (efx->net_dev->features & NETIF_F_RXHASH)
                        skb->rxhash = efx_rx_buf_hash(eh);

                /* Move past the ethernet header. rx_buf->data still points
                 * at the ethernet header */
                skb->protocol = eth_type_trans(skb, efx->net_dev);

                skb_record_rx_queue(skb, channel->rx_queue.core_index);
        }

        if (unlikely(!(efx->net_dev->features & NETIF_F_RXCSUM)))
                rx_buf->flags &= ~EFX_RX_PKT_CSUMMED;

        if (likely(rx_buf->flags & (EFX_RX_BUF_PAGE | EFX_RX_PKT_CSUMMED)) &&
            !channel->type->receive_skb)
                efx_rx_packet_gro(channel, rx_buf, eh);
        else
                efx_rx_deliver(channel, rx_buf);
}

void efx_rx_strategy(struct efx_channel *channel)
{
        enum efx_rx_alloc_method method = rx_alloc_method;

        if (channel->type->receive_skb) {
                channel->rx_alloc_push_pages = false;
                return;
        }

        /* Only makes sense to use page based allocation if GRO is enabled */
        if (!(channel->efx->net_dev->features & NETIF_F_GRO)) {
                method = RX_ALLOC_METHOD_SKB;
        } else if (method == RX_ALLOC_METHOD_AUTO) {
                /* Constrain the rx_alloc_level */
                if (channel->rx_alloc_level < 0)
                        channel->rx_alloc_level = 0;
                else if (channel->rx_alloc_level > RX_ALLOC_LEVEL_MAX)
                        channel->rx_alloc_level = RX_ALLOC_LEVEL_MAX;

                /* Decide on the allocation method */
                method = ((channel->rx_alloc_level > RX_ALLOC_LEVEL_GRO) ?
                          RX_ALLOC_METHOD_PAGE : RX_ALLOC_METHOD_SKB);
        }

        /* Push the option */
        channel->rx_alloc_push_pages = (method == RX_ALLOC_METHOD_PAGE);
}

int efx_probe_rx_queue(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned int entries;
        int rc;

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

        netif_dbg(efx, probe, efx->net_dev,
                  "creating RX queue %d size %#x mask %#x\n",
                  efx_rx_queue_index(rx_queue), efx->rxq_entries,
                  rx_queue->ptr_mask);

        /* Allocate RX buffers */
        rx_queue->buffer = kcalloc(entries, sizeof(*rx_queue->buffer),
                                   GFP_KERNEL);
        if (!rx_queue->buffer)
                return -ENOMEM;

        rc = efx_nic_probe_rx(rx_queue);
        if (rc) {
                kfree(rx_queue->buffer);
                rx_queue->buffer = NULL;
        }
        return rc;
}

void efx_init_rx_queue(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        unsigned int max_fill, trigger, max_trigger;

        netif_dbg(rx_queue->efx, drv, rx_queue->efx->net_dev,
                  "initialising RX queue %d\n", efx_rx_queue_index(rx_queue));

        /* Initialise ptr fields */
        rx_queue->added_count = 0;
        rx_queue->notified_count = 0;
        rx_queue->removed_count = 0;
        rx_queue->min_fill = -1U;

        /* Initialise limit fields */
        max_fill = efx->rxq_entries - EFX_RXD_HEAD_ROOM;
        max_trigger = max_fill - EFX_RX_BATCH;
        if (rx_refill_threshold != 0) {
                trigger = max_fill * min(rx_refill_threshold, 100U) / 100U;
                if (trigger > max_trigger)
                        trigger = max_trigger;
        } else {
                trigger = max_trigger;
        }

        rx_queue->max_fill = max_fill;
        rx_queue->fast_fill_trigger = trigger;

        /* Set up RX descriptor ring */
        rx_queue->enabled = true;
        efx_nic_init_rx(rx_queue);
}

void efx_fini_rx_queue(struct efx_rx_queue *rx_queue)
{
        int i;
        struct efx_rx_buffer *rx_buf;

        netif_dbg(rx_queue->efx, drv, rx_queue->efx->net_dev,
                  "shutting down RX queue %d\n", efx_rx_queue_index(rx_queue));

        /* A flush failure might have left rx_queue->enabled */
        rx_queue->enabled = false;

        del_timer_sync(&rx_queue->slow_fill);
        efx_nic_fini_rx(rx_queue);

        /* Release RX buffers NB start at index 0 not current HW ptr */
        if (rx_queue->buffer) {
                for (i = 0; i <= rx_queue->ptr_mask; i++) {
                        rx_buf = efx_rx_buffer(rx_queue, i);
                        efx_fini_rx_buffer(rx_queue, rx_buf);
                }
        }
}

void efx_remove_rx_queue(struct efx_rx_queue *rx_queue)
{
        netif_dbg(rx_queue->efx, drv, rx_queue->efx->net_dev,
                  "destroying RX queue %d\n", efx_rx_queue_index(rx_queue));

        efx_nic_remove_rx(rx_queue);

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


module_param(rx_alloc_method, int, 0644);
MODULE_PARM_DESC(rx_alloc_method, "Allocation method used for RX buffers");

module_param(rx_refill_threshold, uint, 0444);
MODULE_PARM_DESC(rx_refill_threshold,
                 "RX descriptor ring refill threshold (%)");