[mirror_ubuntu-bionic-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 <linux/iommu.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"

/* Preferred number of descriptors to fill at once */
#define EFX_RX_PREFERRED_BATCH 8U

/* Number of RX buffers to recycle pages for.  When creating the RX page recycle
 * ring, this number is divided by the number of buffers per page to calculate
 * the number of pages to store in the RX page recycle ring.
 */
#define EFX_RECYCLE_RING_SIZE_IOMMU 4096
#define EFX_RECYCLE_RING_SIZE_NOIOMMU (2 * EFX_RX_PREFERRED_BATCH)

/* Size of buffer allocated for skb header area. */
#define EFX_SKB_HEADERS  128u

/* 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;

/* Each packet can consume up to ceil(max_frame_len / buffer_size) buffers */
#define EFX_RX_MAX_FRAGS DIV_ROUND_UP(EFX_MAX_FRAME_LEN(EFX_MAX_MTU), \
                                      EFX_RX_USR_BUF_SIZE)

/*
 * RX maximum head room required.
 *
 * This must be at least 1 to prevent overflow, plus one packet-worth
 * to allow pipelined receives.
 */
#define EFX_RXD_HEAD_ROOM (1 + EFX_RX_MAX_FRAGS)

static inline u8 *efx_rx_buf_va(struct efx_rx_buffer *buf)
{
        return page_address(buf->page) + buf->page_offset;
}

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
}

static inline struct efx_rx_buffer *
efx_rx_buf_next(struct efx_rx_queue *rx_queue, struct efx_rx_buffer *rx_buf)
{
        if (unlikely(rx_buf == efx_rx_buffer(rx_queue, rx_queue->ptr_mask)))
                return efx_rx_buffer(rx_queue, 0);
        else
                return rx_buf + 1;
}

static inline void efx_sync_rx_buffer(struct efx_nic *efx,
                                      struct efx_rx_buffer *rx_buf,
                                      unsigned int len)
{
        dma_sync_single_for_cpu(&efx->pci_dev->dev, rx_buf->dma_addr, len,
                                DMA_FROM_DEVICE);
}

void efx_rx_config_page_split(struct efx_nic *efx)
{
        efx->rx_page_buf_step = ALIGN(efx->rx_dma_len + NET_IP_ALIGN,
                                      EFX_RX_BUF_ALIGNMENT);
        efx->rx_bufs_per_page = efx->rx_buffer_order ? 1 :
                ((PAGE_SIZE - sizeof(struct efx_rx_page_state)) /
                 efx->rx_page_buf_step);
        efx->rx_buffer_truesize = (PAGE_SIZE << efx->rx_buffer_order) /
                efx->rx_bufs_per_page;
        efx->rx_pages_per_batch = DIV_ROUND_UP(EFX_RX_PREFERRED_BATCH,
                                               efx->rx_bufs_per_page);
}

/* Check the RX page recycle ring for a page that can be reused. */
static struct page *efx_reuse_page(struct efx_rx_queue *rx_queue)
{
        struct efx_nic *efx = rx_queue->efx;
        struct page *page;
        struct efx_rx_page_state *state;
        unsigned index;

        index = rx_queue->page_remove & rx_queue->page_ptr_mask;
        page = rx_queue->page_ring[index];
        if (page == NULL)
                return NULL;

        rx_queue->page_ring[index] = NULL;
        /* page_remove cannot exceed page_add. */
        if (rx_queue->page_remove != rx_queue->page_add)
                ++rx_queue->page_remove;

        /* If page_count is 1 then we hold the only reference to this page. */
        if (page_count(page) == 1) {
                ++rx_queue->page_recycle_count;
                return page;
        } else {
                state = page_address(page);
                dma_unmap_page(&efx->pci_dev->dev, state->dma_addr,
                               PAGE_SIZE << efx->rx_buffer_order,
                               DMA_FROM_DEVICE);
                put_page(page);
                ++rx_queue->page_recycle_failed;
        }

        return NULL;
}

/**
 * efx_init_rx_buffers - create EFX_RX_BATCH page-based RX buffers
 *
 * @rx_queue:           Efx RX queue
 *
 * This allocates a batch of pages, 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 used for multiple buffers,
 * then the page will either be inserted fully, or not at all.
 */
static int efx_init_rx_buffers(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;

        count = 0;
        do {
                page = efx_reuse_page(rx_queue);
                if (page == NULL) {
                        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,
                                             PAGE_SIZE << efx->rx_buffer_order,
                                             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->dma_addr = dma_addr;
                } else {
                        state = page_address(page);
                        dma_addr = state->dma_addr;
                }

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

                do {
                        index = rx_queue->added_count & rx_queue->ptr_mask;
                        rx_buf = efx_rx_buffer(rx_queue, index);
                        rx_buf->dma_addr = dma_addr + NET_IP_ALIGN;
                        rx_buf->page = page;
                        rx_buf->page_offset = page_offset + NET_IP_ALIGN;
                        rx_buf->len = efx->rx_dma_len;
                        rx_buf->flags = 0;
                        ++rx_queue->added_count;
                        get_page(page);
                        dma_addr += efx->rx_page_buf_step;
                        page_offset += efx->rx_page_buf_step;
                } while (page_offset + efx->rx_page_buf_step <= PAGE_SIZE);

                rx_buf->flags = EFX_RX_BUF_LAST_IN_PAGE;
        } while (++count < efx->rx_pages_per_batch);

        return 0;
}

/* Unmap a DMA-mapped page.  This function is only called for the final RX
 * buffer in a page.
 */
static void efx_unmap_rx_buffer(struct efx_nic *efx,
                                struct efx_rx_buffer *rx_buf)
{
        struct page *page = rx_buf->page;

        if (page) {
                struct efx_rx_page_state *state = page_address(page);
                dma_unmap_page(&efx->pci_dev->dev,
                               state->dma_addr,
                               PAGE_SIZE << efx->rx_buffer_order,
                               DMA_FROM_DEVICE);
        }
}

static void efx_free_rx_buffer(struct efx_rx_buffer *rx_buf)
{
        if (rx_buf->page) {
                put_page(rx_buf->page);
                rx_buf->page = NULL;
        }
}

/* Attempt to recycle the page if there is an RX recycle ring; the page can
 * only be added if this is the final RX buffer, to prevent pages being used in
 * the descriptor ring and appearing in the recycle ring simultaneously.
 */
static void efx_recycle_rx_page(struct efx_channel *channel,
                                struct efx_rx_buffer *rx_buf)
{
        struct page *page = rx_buf->page;
        struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);
        struct efx_nic *efx = rx_queue->efx;
        unsigned index;

        /* Only recycle the page after processing the final buffer. */
        if (!(rx_buf->flags & EFX_RX_BUF_LAST_IN_PAGE))
                return;

        index = rx_queue->page_add & rx_queue->page_ptr_mask;
        if (rx_queue->page_ring[index] == NULL) {
                unsigned read_index = rx_queue->page_remove &
                        rx_queue->page_ptr_mask;

                /* The next slot in the recycle ring is available, but
                 * increment page_remove if the read pointer currently
                 * points here.
                 */
                if (read_index == index)
                        ++rx_queue->page_remove;
                rx_queue->page_ring[index] = page;
                ++rx_queue->page_add;
                return;
        }
        ++rx_queue->page_recycle_full;
        efx_unmap_rx_buffer(efx, rx_buf);
        put_page(rx_buf->page);
}

static void efx_fini_rx_buffer(struct efx_rx_queue *rx_queue,
                               struct efx_rx_buffer *rx_buf)
{
        /* Release the page reference we hold for the buffer. */
        if (rx_buf->page)
                put_page(rx_buf->page);

        /* If this is the last buffer in a page, unmap and free it. */
        if (rx_buf->flags & EFX_RX_BUF_LAST_IN_PAGE) {
                efx_unmap_rx_buffer(rx_queue->efx, rx_buf);
                efx_free_rx_buffer(rx_buf);
        }
        rx_buf->page = NULL;
}

/* Recycle the pages that are used by buffers that have just been received. */
static void efx_recycle_rx_pages(struct efx_channel *channel,
                                 struct efx_rx_buffer *rx_buf,
                                 unsigned int n_frags)
{
        struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);

        do {
                efx_recycle_rx_page(channel, rx_buf);
                rx_buf = efx_rx_buf_next(rx_queue, rx_buf);
        } while (--n_frags);
}

static void efx_discard_rx_packet(struct efx_channel *channel,
                                  struct efx_rx_buffer *rx_buf,
                                  unsigned int n_frags)
{
        struct efx_rx_queue *rx_queue = efx_channel_get_rx_queue(channel);

        efx_recycle_rx_pages(channel, rx_buf, n_frags);

        do {
                efx_free_rx_buffer(rx_buf);
                rx_buf = efx_rx_buf_next(rx_queue, rx_buf);
        } while (--n_frags);
}

/**
 * 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_nic *efx = rx_queue->efx;
        unsigned int fill_level, batch_size;
        int space, rc = 0;

        if (!rx_queue->refill_enabled)
                return;

        /* 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;
        }

        batch_size = efx->rx_pages_per_batch * efx->rx_bufs_per_page;
        space = rx_queue->max_fill - fill_level;
        EFX_BUG_ON_PARANOID(space < batch_size);

        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\n",
                   efx_rx_queue_index(rx_queue), fill_level,
                   rx_queue->max_fill);


        do {
                rc = efx_init_rx_buffers(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 -= batch_size) >= batch_size);

        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)
{
        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);
                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,
                  unsigned int n_frags, u8 *eh)
{
        struct napi_struct *napi = &channel->napi_str;
        gro_result_t gro_result;
        struct efx_nic *efx = channel->efx;
        struct sk_buff *skb;

        skb = napi_get_frags(napi);
        if (unlikely(!skb)) {
                while (n_frags--) {
                        put_page(rx_buf->page);
                        rx_buf->page = NULL;
                        rx_buf = efx_rx_buf_next(&channel->rx_queue, rx_buf);
                }
                return;
        }

        if (efx->net_dev->features & NETIF_F_RXHASH)
                skb->rxhash = efx_rx_buf_hash(eh);
        skb->ip_summed = ((rx_buf->flags & EFX_RX_PKT_CSUMMED) ?
                          CHECKSUM_UNNECESSARY : CHECKSUM_NONE);

        for (;;) {
                skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags,
                                   rx_buf->page, rx_buf->page_offset,
                                   rx_buf->len);
                rx_buf->page = NULL;
                skb->len += rx_buf->len;
                if (skb_shinfo(skb)->nr_frags == n_frags)
                        break;

                rx_buf = efx_rx_buf_next(&channel->rx_queue, rx_buf);
        }

        skb->data_len = skb->len;
        skb->truesize += n_frags * efx->rx_buffer_truesize;

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

        gro_result = napi_gro_frags(napi);
        if (gro_result != GRO_DROP)
                channel->irq_mod_score += 2;
}

/* Allocate and construct an SKB around page fragments */
static struct sk_buff *efx_rx_mk_skb(struct efx_channel *channel,
                                     struct efx_rx_buffer *rx_buf,
                                     unsigned int n_frags,
                                     u8 *eh, int hdr_len)
{
        struct efx_nic *efx = channel->efx;
        struct sk_buff *skb;

        /* Allocate an SKB to store the headers */
        skb = netdev_alloc_skb(efx->net_dev, hdr_len + EFX_PAGE_SKB_ALIGN);
        if (unlikely(skb == NULL))
                return NULL;

        EFX_BUG_ON_PARANOID(rx_buf->len < hdr_len);

        skb_reserve(skb, EFX_PAGE_SKB_ALIGN);
        memcpy(__skb_put(skb, hdr_len), eh, hdr_len);

        /* Append the remaining page(s) onto the frag list */
        if (rx_buf->len > hdr_len) {
                rx_buf->page_offset += hdr_len;
                rx_buf->len -= hdr_len;

                for (;;) {
                        skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags,
                                           rx_buf->page, rx_buf->page_offset,
                                           rx_buf->len);
                        rx_buf->page = NULL;
                        skb->len += rx_buf->len;
                        skb->data_len += rx_buf->len;
                        if (skb_shinfo(skb)->nr_frags == n_frags)
                                break;

                        rx_buf = efx_rx_buf_next(&channel->rx_queue, rx_buf);
                }
        } else {
                __free_pages(rx_buf->page, efx->rx_buffer_order);
                rx_buf->page = NULL;
                n_frags = 0;
        }

        skb->truesize += n_frags * efx->rx_buffer_truesize;

        /* Move past the ethernet header */
        skb->protocol = eth_type_trans(skb, efx->net_dev);

        return skb;
}

void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
                   unsigned int n_frags, 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;

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

        /* Validate the number of fragments and completed length */
        if (n_frags == 1) {
                efx_rx_packet__check_len(rx_queue, rx_buf, len);
        } else if (unlikely(n_frags > EFX_RX_MAX_FRAGS) ||
                   unlikely(len <= (n_frags - 1) * EFX_RX_USR_BUF_SIZE) ||
                   unlikely(len > n_frags * EFX_RX_USR_BUF_SIZE) ||
                   unlikely(!efx->rx_scatter)) {
                /* If this isn't an explicit discard request, either
                 * the hardware or the driver is broken.
                 */
                WARN_ON(!(len == 0 && rx_buf->flags & EFX_RX_PKT_DISCARD));
                rx_buf->flags |= EFX_RX_PKT_DISCARD;
        }

        netif_vdbg(efx, rx_status, efx->net_dev,
                   "RX queue %d received ids %x-%x len %d %s%s\n",
                   efx_rx_queue_index(rx_queue), index,
                   (index + n_frags - 1) & rx_queue->ptr_mask, len,
                   (rx_buf->flags & EFX_RX_PKT_CSUMMED) ? " [SUMMED]" : "",
                   (rx_buf->flags & EFX_RX_PKT_DISCARD) ? " [DISCARD]" : "");

        /* Discard packet, if instructed to do so.  Process the
         * previous receive first.
         */
        if (unlikely(rx_buf->flags & EFX_RX_PKT_DISCARD)) {
                efx_rx_flush_packet(channel);
                efx_discard_rx_packet(channel, rx_buf, n_frags);
                return;
        }

        if (n_frags == 1)
                rx_buf->len = len;

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

        rx_buf->page_offset += efx->type->rx_buffer_hash_size;
        rx_buf->len -= efx->type->rx_buffer_hash_size;

        if (n_frags > 1) {
                /* Release/sync DMA mapping for additional fragments.
                 * Fix length for last fragment.
                 */
                unsigned int tail_frags = n_frags - 1;

                for (;;) {
                        rx_buf = efx_rx_buf_next(rx_queue, rx_buf);
                        if (--tail_frags == 0)
                                break;
                        efx_sync_rx_buffer(efx, rx_buf, EFX_RX_USR_BUF_SIZE);
                }
                rx_buf->len = len - (n_frags - 1) * EFX_RX_USR_BUF_SIZE;
                efx_sync_rx_buffer(efx, rx_buf, rx_buf->len);
        }

        /* All fragments have been DMA-synced, so recycle pages. */
        rx_buf = efx_rx_buffer(rx_queue, index);
        efx_recycle_rx_pages(channel, rx_buf, n_frags);

        /* Pipeline receives so that we give time for packet headers to be
         * prefetched into cache.
         */
        efx_rx_flush_packet(channel);
        channel->rx_pkt_n_frags = n_frags;
        channel->rx_pkt_index = index;
}

static void efx_rx_deliver(struct efx_channel *channel, u8 *eh,
                           struct efx_rx_buffer *rx_buf,
                           unsigned int n_frags)
{
        struct sk_buff *skb;
        u16 hdr_len = min_t(u16, rx_buf->len, EFX_SKB_HEADERS);

        skb = efx_rx_mk_skb(channel, rx_buf, n_frags, eh, hdr_len);
        if (unlikely(skb == NULL)) {
                efx_free_rx_buffer(rx_buf);
                return;
        }
        skb_record_rx_queue(skb, channel->rx_queue.core_index);

        /* Set the SKB flags */
        skb_checksum_none_assert(skb);
        if (likely(rx_buf->flags & EFX_RX_PKT_CSUMMED))
                skb->ip_summed = CHECKSUM_UNNECESSARY;

        if (channel->type->receive_skb)
                if (channel->type->receive_skb(channel, skb))
                        return;

        /* Pass the packet up */
        netif_receive_skb(skb);
}

/* Handle a received packet.  Second half: Touches packet payload. */
void __efx_rx_packet(struct efx_channel *channel)
{
        struct efx_nic *efx = channel->efx;
        struct efx_rx_buffer *rx_buf =
                efx_rx_buffer(&channel->rx_queue, channel->rx_pkt_index);
        u8 *eh = efx_rx_buf_va(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(rx_buf);
                goto out;
        }

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

        if ((rx_buf->flags & EFX_RX_PKT_TCP) && !channel->type->receive_skb)
                efx_rx_packet_gro(channel, rx_buf, channel->rx_pkt_n_frags, eh);
        else
                efx_rx_deliver(channel, eh, rx_buf, channel->rx_pkt_n_frags);
out:
        channel->rx_pkt_n_frags = 0;
}

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;
}

static void efx_init_rx_recycle_ring(struct efx_nic *efx,
                                     struct efx_rx_queue *rx_queue)
{
        unsigned int bufs_in_recycle_ring, page_ring_size;

        /* Set the RX recycle ring size */
#ifdef CONFIG_PPC64
        bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_IOMMU;
#else
        if (iommu_present(&pci_bus_type))
                bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_IOMMU;
        else
                bufs_in_recycle_ring = EFX_RECYCLE_RING_SIZE_NOIOMMU;
#endif /* CONFIG_PPC64 */

        page_ring_size = roundup_pow_of_two(bufs_in_recycle_ring /
                                            efx->rx_bufs_per_page);
        rx_queue->page_ring = kcalloc(page_ring_size,
                                      sizeof(*rx_queue->page_ring), GFP_KERNEL);
        rx_queue->page_ptr_mask = page_ring_size - 1;
}

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;
        efx_init_rx_recycle_ring(efx, rx_queue);

        rx_queue->page_remove = 0;
        rx_queue->page_add = rx_queue->page_ptr_mask + 1;
        rx_queue->page_recycle_count = 0;
        rx_queue->page_recycle_failed = 0;
        rx_queue->page_recycle_full = 0;

        /* Initialise limit fields */
        max_fill = efx->rxq_entries - EFX_RXD_HEAD_ROOM;
        max_trigger =
                max_fill - efx->rx_pages_per_batch * efx->rx_bufs_per_page;
        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;
        rx_queue->refill_enabled = true;

        /* Set up RX descriptor ring */
        efx_nic_init_rx(rx_queue);
}

void efx_fini_rx_queue(struct efx_rx_queue *rx_queue)
{
        int i;
        struct efx_nic *efx = rx_queue->efx;
        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));

        del_timer_sync(&rx_queue->slow_fill);

        /* Release RX buffers from the current read ptr to the write ptr */
        if (rx_queue->buffer) {
                for (i = rx_queue->removed_count; i < rx_queue->added_count;
                     i++) {
                        unsigned index = i & rx_queue->ptr_mask;
                        rx_buf = efx_rx_buffer(rx_queue, index);
                        efx_fini_rx_buffer(rx_queue, rx_buf);
                }
        }

        /* Unmap and release the pages in the recycle ring. Remove the ring. */
        for (i = 0; i <= rx_queue->page_ptr_mask; i++) {
                struct page *page = rx_queue->page_ring[i];
                struct efx_rx_page_state *state;

                if (page == NULL)
                        continue;

                state = page_address(page);
                dma_unmap_page(&efx->pci_dev->dev, state->dma_addr,
                               PAGE_SIZE << efx->rx_buffer_order,
                               DMA_FROM_DEVICE);
                put_page(page);
        }
        kfree(rx_queue->page_ring);
        rx_queue->page_ring = NULL;
}

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