[dpdk.git] / lib / librte_pmd_e1000 / em_rxtx.c

/*-
 *   BSD LICENSE
 *
 *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
 *   All rights reserved.
 *
 *   Redistribution and use in source and binary forms, with or without
 *   modification, are permitted provided that the following conditions
 *   are met:
 *
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in
 *       the documentation and/or other materials provided with the
 *       distribution.
 *     * Neither the name of Intel Corporation nor the names of its
 *       contributors may be used to endorse or promote products derived
 *       from this software without specific prior written permission.
 *
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 *   A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 *   OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *   DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *   THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/queue.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <stdarg.h>
#include <inttypes.h>

#include <rte_interrupts.h>
#include <rte_byteorder.h>
#include <rte_common.h>
#include <rte_log.h>
#include <rte_debug.h>
#include <rte_pci.h>
#include <rte_memory.h>
#include <rte_memcpy.h>
#include <rte_memzone.h>
#include <rte_launch.h>
#include <rte_tailq.h>
#include <rte_eal.h>
#include <rte_per_lcore.h>
#include <rte_lcore.h>
#include <rte_atomic.h>
#include <rte_branch_prediction.h>
#include <rte_ring.h>
#include <rte_mempool.h>
#include <rte_malloc.h>
#include <rte_mbuf.h>
#include <rte_ether.h>
#include <rte_ethdev.h>
#include <rte_prefetch.h>
#include <rte_ip.h>
#include <rte_udp.h>
#include <rte_tcp.h>
#include <rte_sctp.h>
#include <rte_string_fns.h>

#include "e1000_logs.h"
#include "e1000/e1000_api.h"
#include "e1000_ethdev.h"
#include "e1000/e1000_osdep.h"

#define E1000_TXD_VLAN_SHIFT    16

#define E1000_RXDCTL_GRAN       0x01000000 /* RXDCTL Granularity */

static inline struct rte_mbuf *
rte_rxmbuf_alloc(struct rte_mempool *mp)
{
        struct rte_mbuf *m;

        m = __rte_mbuf_raw_alloc(mp);
        __rte_mbuf_sanity_check_raw(m, 0);
        return (m);
}

#define RTE_MBUF_DATA_DMA_ADDR(mb)             \
        (uint64_t) ((mb)->buf_physaddr +       \
        (uint64_t) ((char *)((mb)->data) - (char *)(mb)->buf_addr))

#define RTE_MBUF_DATA_DMA_ADDR_DEFAULT(mb) \
        (uint64_t) ((mb)->buf_physaddr + RTE_PKTMBUF_HEADROOM)

/**
 * Structure associated with each descriptor of the RX ring of a RX queue.
 */
struct em_rx_entry {
        struct rte_mbuf *mbuf; /**< mbuf associated with RX descriptor. */
};

/**
 * Structure associated with each descriptor of the TX ring of a TX queue.
 */
struct em_tx_entry {
        struct rte_mbuf *mbuf; /**< mbuf associated with TX desc, if any. */
        uint16_t next_id; /**< Index of next descriptor in ring. */
        uint16_t last_id; /**< Index of last scattered descriptor. */
};

/**
 * Structure associated with each RX queue.
 */
struct em_rx_queue {
        struct rte_mempool  *mb_pool;   /**< mbuf pool to populate RX ring. */
        volatile struct e1000_rx_desc *rx_ring; /**< RX ring virtual address. */
        uint64_t            rx_ring_phys_addr; /**< RX ring DMA address. */
        volatile uint32_t   *rdt_reg_addr; /**< RDT register address. */
        volatile uint32_t   *rdh_reg_addr; /**< RDH register address. */
        struct em_rx_entry *sw_ring;   /**< address of RX software ring. */
        struct rte_mbuf *pkt_first_seg; /**< First segment of current packet. */
        struct rte_mbuf *pkt_last_seg;  /**< Last segment of current packet. */
        uint16_t            nb_rx_desc; /**< number of RX descriptors. */
        uint16_t            rx_tail;    /**< current value of RDT register. */
        uint16_t            nb_rx_hold; /**< number of held free RX desc. */
        uint16_t            rx_free_thresh; /**< max free RX desc to hold. */
        uint16_t            queue_id;   /**< RX queue index. */
        uint8_t             port_id;    /**< Device port identifier. */
        uint8_t             pthresh;    /**< Prefetch threshold register. */
        uint8_t             hthresh;    /**< Host threshold register. */
        uint8_t             wthresh;    /**< Write-back threshold register. */
        uint8_t             crc_len;    /**< 0 if CRC stripped, 4 otherwise. */
};

/**
 * Hardware context number
 */
enum {
        EM_CTX_0    = 0, /**< CTX0 */
        EM_CTX_NUM  = 1, /**< CTX NUM */
};

/** Offload features */
union em_vlan_macip {
        uint32_t data;
        struct {
                uint16_t l3_len:9; /**< L3 (IP) Header Length. */
                uint16_t l2_len:7; /**< L2 (MAC) Header Length. */
                uint16_t vlan_tci;
                /**< VLAN Tag Control Identifier (CPU order). */
        } f;
};

/*
 * Compare mask for vlan_macip_len.data,
 * should be in sync with em_vlan_macip.f layout.
 * */
#define TX_VLAN_CMP_MASK        0xFFFF0000  /**< VLAN length - 16-bits. */
#define TX_MAC_LEN_CMP_MASK     0x0000FE00  /**< MAC length - 7-bits. */
#define TX_IP_LEN_CMP_MASK      0x000001FF  /**< IP  length - 9-bits. */
/** MAC+IP  length. */
#define TX_MACIP_LEN_CMP_MASK   (TX_MAC_LEN_CMP_MASK | TX_IP_LEN_CMP_MASK)

/**
 * Structure to check if new context need be built
 */
struct em_ctx_info {
        uint16_t flags;              /**< ol_flags related to context build. */
        uint32_t cmp_mask;           /**< compare mask */
        union em_vlan_macip hdrlen;  /**< L2 and L3 header lenghts */
};

/**
 * Structure associated with each TX queue.
 */
struct em_tx_queue {
        volatile struct e1000_data_desc *tx_ring; /**< TX ring address */
        uint64_t               tx_ring_phys_addr; /**< TX ring DMA address. */
        struct em_tx_entry    *sw_ring; /**< virtual address of SW ring. */
        volatile uint32_t      *tdt_reg_addr; /**< Address of TDT register. */
        uint16_t               nb_tx_desc;    /**< number of TX descriptors. */
        uint16_t               tx_tail;  /**< Current value of TDT register. */
        uint16_t               tx_free_thresh;/**< minimum TX before freeing. */
        /**< Number of TX descriptors to use before RS bit is set. */
        uint16_t               tx_rs_thresh;
        /** Number of TX descriptors used since RS bit was set. */
        uint16_t               nb_tx_used;
        /** Index to last TX descriptor to have been cleaned. */
        uint16_t               last_desc_cleaned;
        /** Total number of TX descriptors ready to be allocated. */
        uint16_t               nb_tx_free;
        uint16_t               queue_id; /**< TX queue index. */
        uint8_t                port_id;  /**< Device port identifier. */
        uint8_t                pthresh;  /**< Prefetch threshold register. */
        uint8_t                hthresh;  /**< Host threshold register. */
        uint8_t                wthresh;  /**< Write-back threshold register. */
        struct em_ctx_info ctx_cache;
        /**< Hardware context history.*/
};

#if 1
#define RTE_PMD_USE_PREFETCH
#endif

#ifdef RTE_PMD_USE_PREFETCH
#define rte_em_prefetch(p)      rte_prefetch0(p)
#else
#define rte_em_prefetch(p)      do {} while(0)
#endif

#ifdef RTE_PMD_PACKET_PREFETCH
#define rte_packet_prefetch(p) rte_prefetch1(p)
#else
#define rte_packet_prefetch(p)  do {} while(0)
#endif

#ifndef DEFAULT_TX_FREE_THRESH
#define DEFAULT_TX_FREE_THRESH  32
#endif /* DEFAULT_TX_FREE_THRESH */

#ifndef DEFAULT_TX_RS_THRESH
#define DEFAULT_TX_RS_THRESH  32
#endif /* DEFAULT_TX_RS_THRESH */


/*********************************************************************
 *
 *  TX function
 *
 **********************************************************************/

/*
 * Populates TX context descriptor.
 */
static inline void
em_set_xmit_ctx(struct em_tx_queue* txq,
                volatile struct e1000_context_desc *ctx_txd,
                uint16_t flags,
                union em_vlan_macip hdrlen)
{
        uint32_t cmp_mask, cmd_len;
        uint16_t ipcse, l2len;
        struct e1000_context_desc ctx;

        cmp_mask = 0;
        cmd_len = E1000_TXD_CMD_DEXT | E1000_TXD_DTYP_C;

        l2len = hdrlen.f.l2_len;
        ipcse = (uint16_t)(l2len + hdrlen.f.l3_len);

        /* setup IPCS* fields */
        ctx.lower_setup.ip_fields.ipcss = (uint8_t)l2len;
        ctx.lower_setup.ip_fields.ipcso = (uint8_t)(l2len +
                        offsetof(struct ipv4_hdr, hdr_checksum));

        /*
         * When doing checksum or TCP segmentation with IPv6 headers,
         * IPCSE field should be set t0 0.
         */
        if (flags & PKT_TX_IP_CKSUM) {
                ctx.lower_setup.ip_fields.ipcse =
                        (uint16_t)rte_cpu_to_le_16(ipcse - 1);
                cmd_len |= E1000_TXD_CMD_IP;
                cmp_mask |= TX_MACIP_LEN_CMP_MASK;
        } else {
                ctx.lower_setup.ip_fields.ipcse = 0;
        }

        /* setup TUCS* fields */
        ctx.upper_setup.tcp_fields.tucss = (uint8_t)ipcse;
        ctx.upper_setup.tcp_fields.tucse = 0;

        switch (flags & PKT_TX_L4_MASK) {
        case PKT_TX_UDP_CKSUM:
                ctx.upper_setup.tcp_fields.tucso = (uint8_t)(ipcse +
                                offsetof(struct udp_hdr, dgram_cksum));
                cmp_mask |= TX_MACIP_LEN_CMP_MASK;
                break;
        case PKT_TX_TCP_CKSUM:
                ctx.upper_setup.tcp_fields.tucso = (uint8_t)(ipcse +
                                offsetof(struct tcp_hdr, cksum));
                cmd_len |= E1000_TXD_CMD_TCP;
                cmp_mask |= TX_MACIP_LEN_CMP_MASK;
                break;
        default:
                ctx.upper_setup.tcp_fields.tucso = 0;
        }

        ctx.cmd_and_length = rte_cpu_to_le_32(cmd_len);
        ctx.tcp_seg_setup.data = 0;

        *ctx_txd = ctx;

        txq->ctx_cache.flags = flags;
        txq->ctx_cache.cmp_mask = cmp_mask;
        txq->ctx_cache.hdrlen = hdrlen;
}

/*
 * Check which hardware context can be used. Use the existing match
 * or create a new context descriptor.
 */
static inline uint32_t
what_ctx_update(struct em_tx_queue *txq, uint16_t flags,
                union em_vlan_macip hdrlen)
{
        /* If match with the current context */
        if (likely (txq->ctx_cache.flags == flags &&
                        ((txq->ctx_cache.hdrlen.data ^ hdrlen.data) &
                        txq->ctx_cache.cmp_mask) == 0))
                return (EM_CTX_0);

        /* Mismatch */
        return (EM_CTX_NUM);
}

/* Reset transmit descriptors after they have been used */
static inline int
em_xmit_cleanup(struct em_tx_queue *txq)
{
        struct em_tx_entry *sw_ring = txq->sw_ring;
        volatile struct e1000_data_desc *txr = txq->tx_ring;
        uint16_t last_desc_cleaned = txq->last_desc_cleaned;
        uint16_t nb_tx_desc = txq->nb_tx_desc;
        uint16_t desc_to_clean_to;
        uint16_t nb_tx_to_clean;

        /* Determine the last descriptor needing to be cleaned */
        desc_to_clean_to = (uint16_t)(last_desc_cleaned + txq->tx_rs_thresh);
        if (desc_to_clean_to >= nb_tx_desc)
                desc_to_clean_to = (uint16_t)(desc_to_clean_to - nb_tx_desc);

        /* Check to make sure the last descriptor to clean is done */
        desc_to_clean_to = sw_ring[desc_to_clean_to].last_id;
        if (! (txr[desc_to_clean_to].upper.fields.status & E1000_TXD_STAT_DD))
        {
                PMD_TX_FREE_LOG(DEBUG,
                                "TX descriptor %4u is not done"
                                "(port=%d queue=%d)",
                                desc_to_clean_to,
                                txq->port_id, txq->queue_id);
                /* Failed to clean any descriptors, better luck next time */
                return -(1);
        }

        /* Figure out how many descriptors will be cleaned */
        if (last_desc_cleaned > desc_to_clean_to)
                nb_tx_to_clean = (uint16_t)((nb_tx_desc - last_desc_cleaned) +
                                                        desc_to_clean_to);
        else
                nb_tx_to_clean = (uint16_t)(desc_to_clean_to -
                                                last_desc_cleaned);

        PMD_TX_FREE_LOG(DEBUG,
                        "Cleaning %4u TX descriptors: %4u to %4u "
                        "(port=%d queue=%d)",
                        nb_tx_to_clean, last_desc_cleaned, desc_to_clean_to,
                        txq->port_id, txq->queue_id);

        /*
         * The last descriptor to clean is done, so that means all the
         * descriptors from the last descriptor that was cleaned
         * up to the last descriptor with the RS bit set
         * are done. Only reset the threshold descriptor.
         */
        txr[desc_to_clean_to].upper.fields.status = 0;

        /* Update the txq to reflect the last descriptor that was cleaned */
        txq->last_desc_cleaned = desc_to_clean_to;
        txq->nb_tx_free = (uint16_t)(txq->nb_tx_free + nb_tx_to_clean);

        /* No Error */
        return (0);
}

static inline uint32_t
tx_desc_cksum_flags_to_upper(uint16_t ol_flags)
{
        static const uint32_t l4_olinfo[2] = {0, E1000_TXD_POPTS_TXSM << 8};
        static const uint32_t l3_olinfo[2] = {0, E1000_TXD_POPTS_IXSM << 8};
        uint32_t tmp;

        tmp = l4_olinfo[(ol_flags & PKT_TX_L4_MASK) != PKT_TX_L4_NO_CKSUM];
        tmp |= l3_olinfo[(ol_flags & PKT_TX_IP_CKSUM) != 0];
        return (tmp);
}

uint16_t
eth_em_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
                uint16_t nb_pkts)
{
        struct em_tx_queue *txq;
        struct em_tx_entry *sw_ring;
        struct em_tx_entry *txe, *txn;
        volatile struct e1000_data_desc *txr;
        volatile struct e1000_data_desc *txd;
        struct rte_mbuf     *tx_pkt;
        struct rte_mbuf     *m_seg;
        uint64_t buf_dma_addr;
        uint32_t popts_spec;
        uint32_t cmd_type_len;
        uint16_t slen;
        uint16_t ol_flags;
        uint16_t tx_id;
        uint16_t tx_last;
        uint16_t nb_tx;
        uint16_t nb_used;
        uint16_t tx_ol_req;
        uint32_t ctx;
        uint32_t new_ctx;
        union em_vlan_macip hdrlen;

        txq = tx_queue;
        sw_ring = txq->sw_ring;
        txr     = txq->tx_ring;
        tx_id   = txq->tx_tail;
        txe = &sw_ring[tx_id];

        /* Determine if the descriptor ring needs to be cleaned. */
        if ((txq->nb_tx_desc - txq->nb_tx_free) > txq->tx_free_thresh) {
                em_xmit_cleanup(txq);
        }

        /* TX loop */
        for (nb_tx = 0; nb_tx < nb_pkts; nb_tx++) {
                new_ctx = 0;
                tx_pkt = *tx_pkts++;

                RTE_MBUF_PREFETCH_TO_FREE(txe->mbuf);

                /*
                 * Determine how many (if any) context descriptors
                 * are needed for offload functionality.
                 */
                ol_flags = tx_pkt->ol_flags;

                /* If hardware offload required */
                tx_ol_req = (uint16_t)(ol_flags & (PKT_TX_IP_CKSUM |
                                                        PKT_TX_L4_MASK));
                if (tx_ol_req) {
                        hdrlen.f.vlan_tci = tx_pkt->vlan_tci;
                        hdrlen.f.l2_len = tx_pkt->l2_len;
                        hdrlen.f.l3_len = tx_pkt->l3_len;
                        /* If new context to be built or reuse the exist ctx. */
                        ctx = what_ctx_update(txq, tx_ol_req, hdrlen);

                        /* Only allocate context descriptor if required*/
                        new_ctx = (ctx == EM_CTX_NUM);
                }

                /*
                 * Keep track of how many descriptors are used this loop
                 * This will always be the number of segments + the number of
                 * Context descriptors required to transmit the packet
                 */
                nb_used = (uint16_t)(tx_pkt->nb_segs + new_ctx);

                /*
                 * The number of descriptors that must be allocated for a
                 * packet is the number of segments of that packet, plus 1
                 * Context Descriptor for the hardware offload, if any.
                 * Determine the last TX descriptor to allocate in the TX ring
                 * for the packet, starting from the current position (tx_id)
                 * in the ring.
                 */
                tx_last = (uint16_t) (tx_id + nb_used - 1);

                /* Circular ring */
                if (tx_last >= txq->nb_tx_desc)
                        tx_last = (uint16_t) (tx_last - txq->nb_tx_desc);

                PMD_TX_LOG(DEBUG, "port_id=%u queue_id=%u pktlen=%u"
                        " tx_first=%u tx_last=%u\n",
                        (unsigned) txq->port_id,
                        (unsigned) txq->queue_id,
                        (unsigned) tx_pkt->pkt_len,
                        (unsigned) tx_id,
                        (unsigned) tx_last);

                /*
                 * Make sure there are enough TX descriptors available to
                 * transmit the entire packet.
                 * nb_used better be less than or equal to txq->tx_rs_thresh
                 */
                while (unlikely (nb_used > txq->nb_tx_free)) {
                        PMD_TX_FREE_LOG(DEBUG,
                                        "Not enough free TX descriptors "
                                        "nb_used=%4u nb_free=%4u "
                                        "(port=%d queue=%d)",
                                        nb_used, txq->nb_tx_free,
                                        txq->port_id, txq->queue_id);

                        if (em_xmit_cleanup(txq) != 0) {
                                /* Could not clean any descriptors */
                                if (nb_tx == 0)
                                        return (0);
                                goto end_of_tx;
                        }
                }

                /*
                 * By now there are enough free TX descriptors to transmit
                 * the packet.
                 */

                /*
                 * Set common flags of all TX Data Descriptors.
                 *
                 * The following bits must be set in all Data Descriptors:
                 *    - E1000_TXD_DTYP_DATA
                 *    - E1000_TXD_DTYP_DEXT
                 *
                 * The following bits must be set in the first Data Descriptor
                 * and are ignored in the other ones:
                 *    - E1000_TXD_POPTS_IXSM
                 *    - E1000_TXD_POPTS_TXSM
                 *
                 * The following bits must be set in the last Data Descriptor
                 * and are ignored in the other ones:
                 *    - E1000_TXD_CMD_VLE
                 *    - E1000_TXD_CMD_IFCS
                 *
                 * The following bits must only be set in the last Data
                 * Descriptor:
                 *   - E1000_TXD_CMD_EOP
                 *
                 * The following bits can be set in any Data Descriptor, but
                 * are only set in the last Data Descriptor:
                 *   - E1000_TXD_CMD_RS
                 */
                cmd_type_len = E1000_TXD_CMD_DEXT | E1000_TXD_DTYP_D |
                        E1000_TXD_CMD_IFCS;
                popts_spec = 0;

                /* Set VLAN Tag offload fields. */
                if (ol_flags & PKT_TX_VLAN_PKT) {
                        cmd_type_len |= E1000_TXD_CMD_VLE;
                        popts_spec = tx_pkt->vlan_tci << E1000_TXD_VLAN_SHIFT;
                }

                if (tx_ol_req) {
                        /*
                         * Setup the TX Context Descriptor if required
                         */
                        if (new_ctx) {
                                volatile struct e1000_context_desc *ctx_txd;

                                ctx_txd = (volatile struct e1000_context_desc *)
                                        &txr[tx_id];

                                txn = &sw_ring[txe->next_id];
                                RTE_MBUF_PREFETCH_TO_FREE(txn->mbuf);

                                if (txe->mbuf != NULL) {
                                        rte_pktmbuf_free_seg(txe->mbuf);
                                        txe->mbuf = NULL;
                                }

                                em_set_xmit_ctx(txq, ctx_txd, tx_ol_req,
                                        hdrlen);

                                txe->last_id = tx_last;
                                tx_id = txe->next_id;
                                txe = txn;
                        }

                        /*
                         * Setup the TX Data Descriptor,
                         * This path will go through
                         * whatever new/reuse the context descriptor
                         */
                        popts_spec |= tx_desc_cksum_flags_to_upper(ol_flags);
                }

                m_seg = tx_pkt;
                do {
                        txd = &txr[tx_id];
                        txn = &sw_ring[txe->next_id];

                        if (txe->mbuf != NULL)
                                rte_pktmbuf_free_seg(txe->mbuf);
                        txe->mbuf = m_seg;

                        /*
                         * Set up Transmit Data Descriptor.
                         */
                        slen = m_seg->data_len;
                        buf_dma_addr = RTE_MBUF_DATA_DMA_ADDR(m_seg);

                        txd->buffer_addr = rte_cpu_to_le_64(buf_dma_addr);
                        txd->lower.data = rte_cpu_to_le_32(cmd_type_len | slen);
                        txd->upper.data = rte_cpu_to_le_32(popts_spec);

                        txe->last_id = tx_last;
                        tx_id = txe->next_id;
                        txe = txn;
                        m_seg = m_seg->next;
                } while (m_seg != NULL);

                /*
                 * The last packet data descriptor needs End Of Packet (EOP)
                 */
                cmd_type_len |= E1000_TXD_CMD_EOP;
                txq->nb_tx_used = (uint16_t)(txq->nb_tx_used + nb_used);
                txq->nb_tx_free = (uint16_t)(txq->nb_tx_free - nb_used);

                /* Set RS bit only on threshold packets' last descriptor */
                if (txq->nb_tx_used >= txq->tx_rs_thresh) {
                        PMD_TX_FREE_LOG(DEBUG,
                                        "Setting RS bit on TXD id="
                                        "%4u (port=%d queue=%d)",
                                        tx_last, txq->port_id, txq->queue_id);

                        cmd_type_len |= E1000_TXD_CMD_RS;

                        /* Update txq RS bit counters */
                        txq->nb_tx_used = 0;
                }
                txd->lower.data |= rte_cpu_to_le_32(cmd_type_len);
        }
end_of_tx:
        rte_wmb();

        /*
         * Set the Transmit Descriptor Tail (TDT)
         */
        PMD_TX_LOG(DEBUG, "port_id=%u queue_id=%u tx_tail=%u nb_tx=%u",
                (unsigned) txq->port_id, (unsigned) txq->queue_id,
                (unsigned) tx_id, (unsigned) nb_tx);
        E1000_PCI_REG_WRITE(txq->tdt_reg_addr, tx_id);
        txq->tx_tail = tx_id;

        return (nb_tx);
}

/*********************************************************************
 *
 *  RX functions
 *
 **********************************************************************/

static inline uint16_t
rx_desc_status_to_pkt_flags(uint32_t rx_status)
{
        uint16_t pkt_flags;

        /* Check if VLAN present */
        pkt_flags = (uint16_t)((rx_status & E1000_RXD_STAT_VP) ?
                                                PKT_RX_VLAN_PKT : 0);

        return pkt_flags;
}

static inline uint16_t
rx_desc_error_to_pkt_flags(uint32_t rx_error)
{
        uint16_t pkt_flags = 0;

        if (rx_error & E1000_RXD_ERR_IPE)
                pkt_flags |= PKT_RX_IP_CKSUM_BAD;
        if (rx_error & E1000_RXD_ERR_TCPE)
                pkt_flags |= PKT_RX_L4_CKSUM_BAD;
        return (pkt_flags);
}

uint16_t
eth_em_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
                uint16_t nb_pkts)
{
        volatile struct e1000_rx_desc *rx_ring;
        volatile struct e1000_rx_desc *rxdp;
        struct em_rx_queue *rxq;
        struct em_rx_entry *sw_ring;
        struct em_rx_entry *rxe;
        struct rte_mbuf *rxm;
        struct rte_mbuf *nmb;
        struct e1000_rx_desc rxd;
        uint64_t dma_addr;
        uint16_t pkt_len;
        uint16_t rx_id;
        uint16_t nb_rx;
        uint16_t nb_hold;
        uint8_t status;

        rxq = rx_queue;

        nb_rx = 0;
        nb_hold = 0;
        rx_id = rxq->rx_tail;
        rx_ring = rxq->rx_ring;
        sw_ring = rxq->sw_ring;
        while (nb_rx < nb_pkts) {
                /*
                 * The order of operations here is important as the DD status
                 * bit must not be read after any other descriptor fields.
                 * rx_ring and rxdp are pointing to volatile data so the order
                 * of accesses cannot be reordered by the compiler. If they were
                 * not volatile, they could be reordered which could lead to
                 * using invalid descriptor fields when read from rxd.
                 */
                rxdp = &rx_ring[rx_id];
                status = rxdp->status;
                if (! (status & E1000_RXD_STAT_DD))
                        break;
                rxd = *rxdp;

                /*
                 * End of packet.
                 *
                 * If the E1000_RXD_STAT_EOP flag is not set, the RX packet is
                 * likely to be invalid and to be dropped by the various
                 * validation checks performed by the network stack.
                 *
                 * Allocate a new mbuf to replenish the RX ring descriptor.
                 * If the allocation fails:
                 *    - arrange for that RX descriptor to be the first one
                 *      being parsed the next time the receive function is
                 *      invoked [on the same queue].
                 *
                 *    - Stop parsing the RX ring and return immediately.
                 *
                 * This policy do not drop the packet received in the RX
                 * descriptor for which the allocation of a new mbuf failed.
                 * Thus, it allows that packet to be later retrieved if
                 * mbuf have been freed in the mean time.
                 * As a side effect, holding RX descriptors instead of
                 * systematically giving them back to the NIC may lead to
                 * RX ring exhaustion situations.
                 * However, the NIC can gracefully prevent such situations
                 * to happen by sending specific "back-pressure" flow control
                 * frames to its peer(s).
                 */
                PMD_RX_LOG(DEBUG, "\nport_id=%u queue_id=%u rx_id=%u "
                        "status=0x%x pkt_len=%u\n",
                        (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
                        (unsigned) rx_id, (unsigned) status,
                        (unsigned) rte_le_to_cpu_16(rxd.length));

                nmb = rte_rxmbuf_alloc(rxq->mb_pool);
                if (nmb == NULL) {
                        PMD_RX_LOG(DEBUG, "RX mbuf alloc failed port_id=%u "
                                "queue_id=%u\n",
                                (unsigned) rxq->port_id,
                                (unsigned) rxq->queue_id);
                        rte_eth_devices[rxq->port_id].data->rx_mbuf_alloc_failed++;
                        break;
                }

                nb_hold++;
                rxe = &sw_ring[rx_id];
                rx_id++;
                if (rx_id == rxq->nb_rx_desc)
                        rx_id = 0;

                /* Prefetch next mbuf while processing current one. */
                rte_em_prefetch(sw_ring[rx_id].mbuf);

                /*
                 * When next RX descriptor is on a cache-line boundary,
                 * prefetch the next 4 RX descriptors and the next 8 pointers
                 * to mbufs.
                 */
                if ((rx_id & 0x3) == 0) {
                        rte_em_prefetch(&rx_ring[rx_id]);
                        rte_em_prefetch(&sw_ring[rx_id]);
                }

                /* Rearm RXD: attach new mbuf and reset status to zero. */

                rxm = rxe->mbuf;
                rxe->mbuf = nmb;
                dma_addr =
                        rte_cpu_to_le_64(RTE_MBUF_DATA_DMA_ADDR_DEFAULT(nmb));
                rxdp->buffer_addr = dma_addr;
                rxdp->status = 0;

                /*
                 * Initialize the returned mbuf.
                 * 1) setup generic mbuf fields:
                 *    - number of segments,
                 *    - next segment,
                 *    - packet length,
                 *    - RX port identifier.
                 * 2) integrate hardware offload data, if any:
                 *    - RSS flag & hash,
                 *    - IP checksum flag,
                 *    - VLAN TCI, if any,
                 *    - error flags.
                 */
                pkt_len = (uint16_t) (rte_le_to_cpu_16(rxd.length) -
                                rxq->crc_len);
                rxm->data = (char*) rxm->buf_addr + RTE_PKTMBUF_HEADROOM;
                rte_packet_prefetch(rxm->data);
                rxm->nb_segs = 1;
                rxm->next = NULL;
                rxm->pkt_len = pkt_len;
                rxm->data_len = pkt_len;
                rxm->port = rxq->port_id;

                rxm->ol_flags = rx_desc_status_to_pkt_flags(status);
                rxm->ol_flags = (uint16_t)(rxm->ol_flags |
                                rx_desc_error_to_pkt_flags(rxd.errors));

                /* Only valid if PKT_RX_VLAN_PKT set in pkt_flags */
                rxm->vlan_tci = rte_le_to_cpu_16(rxd.special);

                /*
                 * Store the mbuf address into the next entry of the array
                 * of returned packets.
                 */
                rx_pkts[nb_rx++] = rxm;
        }
        rxq->rx_tail = rx_id;

        /*
         * If the number of free RX descriptors is greater than the RX free
         * threshold of the queue, advance the Receive Descriptor Tail (RDT)
         * register.
         * Update the RDT with the value of the last processed RX descriptor
         * minus 1, to guarantee that the RDT register is never equal to the
         * RDH register, which creates a "full" ring situtation from the
         * hardware point of view...
         */
        nb_hold = (uint16_t) (nb_hold + rxq->nb_rx_hold);
        if (nb_hold > rxq->rx_free_thresh) {
                PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_tail=%u "
                        "nb_hold=%u nb_rx=%u\n",
                        (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
                        (unsigned) rx_id, (unsigned) nb_hold,
                        (unsigned) nb_rx);
                rx_id = (uint16_t) ((rx_id == 0) ?
                        (rxq->nb_rx_desc - 1) : (rx_id - 1));
                E1000_PCI_REG_WRITE(rxq->rdt_reg_addr, rx_id);
                nb_hold = 0;
        }
        rxq->nb_rx_hold = nb_hold;
        return (nb_rx);
}

uint16_t
eth_em_recv_scattered_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
                         uint16_t nb_pkts)
{
        struct em_rx_queue *rxq;
        volatile struct e1000_rx_desc *rx_ring;
        volatile struct e1000_rx_desc *rxdp;
        struct em_rx_entry *sw_ring;
        struct em_rx_entry *rxe;
        struct rte_mbuf *first_seg;
        struct rte_mbuf *last_seg;
        struct rte_mbuf *rxm;
        struct rte_mbuf *nmb;
        struct e1000_rx_desc rxd;
        uint64_t dma; /* Physical address of mbuf data buffer */
        uint16_t rx_id;
        uint16_t nb_rx;
        uint16_t nb_hold;
        uint16_t data_len;
        uint8_t status;

        rxq = rx_queue;

        nb_rx = 0;
        nb_hold = 0;
        rx_id = rxq->rx_tail;
        rx_ring = rxq->rx_ring;
        sw_ring = rxq->sw_ring;

        /*
         * Retrieve RX context of current packet, if any.
         */
        first_seg = rxq->pkt_first_seg;
        last_seg = rxq->pkt_last_seg;

        while (nb_rx < nb_pkts) {
        next_desc:
                /*
                 * The order of operations here is important as the DD status
                 * bit must not be read after any other descriptor fields.
                 * rx_ring and rxdp are pointing to volatile data so the order
                 * of accesses cannot be reordered by the compiler. If they were
                 * not volatile, they could be reordered which could lead to
                 * using invalid descriptor fields when read from rxd.
                 */
                rxdp = &rx_ring[rx_id];
                status = rxdp->status;
                if (! (status & E1000_RXD_STAT_DD))
                        break;
                rxd = *rxdp;

                /*
                 * Descriptor done.
                 *
                 * Allocate a new mbuf to replenish the RX ring descriptor.
                 * If the allocation fails:
                 *    - arrange for that RX descriptor to be the first one
                 *      being parsed the next time the receive function is
                 *      invoked [on the same queue].
                 *
                 *    - Stop parsing the RX ring and return immediately.
                 *
                 * This policy does not drop the packet received in the RX
                 * descriptor for which the allocation of a new mbuf failed.
                 * Thus, it allows that packet to be later retrieved if
                 * mbuf have been freed in the mean time.
                 * As a side effect, holding RX descriptors instead of
                 * systematically giving them back to the NIC may lead to
                 * RX ring exhaustion situations.
                 * However, the NIC can gracefully prevent such situations
                 * to happen by sending specific "back-pressure" flow control
                 * frames to its peer(s).
                 */
                PMD_RX_LOG(DEBUG, "\nport_id=%u queue_id=%u rx_id=%u "
                        "status=0x%x data_len=%u\n",
                        (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
                        (unsigned) rx_id, (unsigned) status,
                        (unsigned) rte_le_to_cpu_16(rxd.length));

                nmb = rte_rxmbuf_alloc(rxq->mb_pool);
                if (nmb == NULL) {
                        PMD_RX_LOG(DEBUG, "RX mbuf alloc failed port_id=%u "
                                "queue_id=%u\n", (unsigned) rxq->port_id,
                                (unsigned) rxq->queue_id);
                        rte_eth_devices[rxq->port_id].data->rx_mbuf_alloc_failed++;
                        break;
                }

                nb_hold++;
                rxe = &sw_ring[rx_id];
                rx_id++;
                if (rx_id == rxq->nb_rx_desc)
                        rx_id = 0;

                /* Prefetch next mbuf while processing current one. */
                rte_em_prefetch(sw_ring[rx_id].mbuf);

                /*
                 * When next RX descriptor is on a cache-line boundary,
                 * prefetch the next 4 RX descriptors and the next 8 pointers
                 * to mbufs.
                 */
                if ((rx_id & 0x3) == 0) {
                        rte_em_prefetch(&rx_ring[rx_id]);
                        rte_em_prefetch(&sw_ring[rx_id]);
                }

                /*
                 * Update RX descriptor with the physical address of the new
                 * data buffer of the new allocated mbuf.
                 */
                rxm = rxe->mbuf;
                rxe->mbuf = nmb;
                dma = rte_cpu_to_le_64(RTE_MBUF_DATA_DMA_ADDR_DEFAULT(nmb));
                rxdp->buffer_addr = dma;
                rxdp->status = 0;

                /*
                 * Set data length & data buffer address of mbuf.
                 */
                data_len = rte_le_to_cpu_16(rxd.length);
                rxm->data_len = data_len;
                rxm->data = (char*) rxm->buf_addr + RTE_PKTMBUF_HEADROOM;

                /*
                 * If this is the first buffer of the received packet,
                 * set the pointer to the first mbuf of the packet and
                 * initialize its context.
                 * Otherwise, update the total length and the number of segments
                 * of the current scattered packet, and update the pointer to
                 * the last mbuf of the current packet.
                 */
                if (first_seg == NULL) {
                        first_seg = rxm;
                        first_seg->pkt_len = data_len;
                        first_seg->nb_segs = 1;
                } else {
                        first_seg->pkt_len += data_len;
                        first_seg->nb_segs++;
                        last_seg->next = rxm;
                }

                /*
                 * If this is not the last buffer of the received packet,
                 * update the pointer to the last mbuf of the current scattered
                 * packet and continue to parse the RX ring.
                 */
                if (! (status & E1000_RXD_STAT_EOP)) {
                        last_seg = rxm;
                        goto next_desc;
                }

                /*
                 * This is the last buffer of the received packet.
                 * If the CRC is not stripped by the hardware:
                 *   - Subtract the CRC length from the total packet length.
                 *   - If the last buffer only contains the whole CRC or a part
                 *     of it, free the mbuf associated to the last buffer.
                 *     If part of the CRC is also contained in the previous
                 *     mbuf, subtract the length of that CRC part from the
                 *     data length of the previous mbuf.
                 */
                rxm->next = NULL;
                if (unlikely(rxq->crc_len > 0)) {
                        first_seg->pkt_len -= ETHER_CRC_LEN;
                        if (data_len <= ETHER_CRC_LEN) {
                                rte_pktmbuf_free_seg(rxm);
                                first_seg->nb_segs--;
                                last_seg->data_len = (uint16_t)
                                        (last_seg->data_len -
                                         (ETHER_CRC_LEN - data_len));
                                last_seg->next = NULL;
                        } else
                                rxm->data_len =
                                        (uint16_t) (data_len - ETHER_CRC_LEN);
                }

                /*
                 * Initialize the first mbuf of the returned packet:
                 *    - RX port identifier,
                 *    - hardware offload data, if any:
                 *      - IP checksum flag,
                 *      - error flags.
                 */
                first_seg->port = rxq->port_id;

                first_seg->ol_flags = rx_desc_status_to_pkt_flags(status);
                first_seg->ol_flags = (uint16_t)(first_seg->ol_flags |
                                        rx_desc_error_to_pkt_flags(rxd.errors));

                /* Only valid if PKT_RX_VLAN_PKT set in pkt_flags */
                rxm->vlan_tci = rte_le_to_cpu_16(rxd.special);

                /* Prefetch data of first segment, if configured to do so. */
                rte_packet_prefetch(first_seg->data);

                /*
                 * Store the mbuf address into the next entry of the array
                 * of returned packets.
                 */
                rx_pkts[nb_rx++] = first_seg;

                /*
                 * Setup receipt context for a new packet.
                 */
                first_seg = NULL;
        }

        /*
         * Record index of the next RX descriptor to probe.
         */
        rxq->rx_tail = rx_id;

        /*
         * Save receive context.
         */
        rxq->pkt_first_seg = first_seg;
        rxq->pkt_last_seg = last_seg;

        /*
         * If the number of free RX descriptors is greater than the RX free
         * threshold of the queue, advance the Receive Descriptor Tail (RDT)
         * register.
         * Update the RDT with the value of the last processed RX descriptor
         * minus 1, to guarantee that the RDT register is never equal to the
         * RDH register, which creates a "full" ring situtation from the
         * hardware point of view...
         */
        nb_hold = (uint16_t) (nb_hold + rxq->nb_rx_hold);
        if (nb_hold > rxq->rx_free_thresh) {
                PMD_RX_LOG(DEBUG, "port_id=%u queue_id=%u rx_tail=%u "
                        "nb_hold=%u nb_rx=%u\n",
                        (unsigned) rxq->port_id, (unsigned) rxq->queue_id,
                        (unsigned) rx_id, (unsigned) nb_hold,
                        (unsigned) nb_rx);
                rx_id = (uint16_t) ((rx_id == 0) ?
                        (rxq->nb_rx_desc - 1) : (rx_id - 1));
                E1000_PCI_REG_WRITE(rxq->rdt_reg_addr, rx_id);
                nb_hold = 0;
        }
        rxq->nb_rx_hold = nb_hold;
        return (nb_rx);
}

/*
 * Rings setup and release.
 *
 * TDBA/RDBA should be aligned on 16 byte boundary. But TDLEN/RDLEN should be
 * multiple of 128 bytes. So we align TDBA/RDBA on 128 byte boundary.
 * This will also optimize cache line size effect.
 * H/W supports up to cache line size 128.
 */
#define EM_ALIGN 128

/*
 * Maximum number of Ring Descriptors.
 *
 * Since RDLEN/TDLEN should be multiple of 128 bytes, the number of ring
 * desscriptors should meet the following condition:
 * (num_ring_desc * sizeof(struct e1000_rx/tx_desc)) % 128 == 0
 */
#define EM_MIN_RING_DESC 32
#define EM_MAX_RING_DESC 4096

#define EM_MAX_BUF_SIZE     16384
#define EM_RCTL_FLXBUF_STEP 1024

static const struct rte_memzone *
ring_dma_zone_reserve(struct rte_eth_dev *dev, const char *ring_name,
                uint16_t queue_id, uint32_t ring_size, int socket_id)
{
        const struct rte_memzone *mz;
        char z_name[RTE_MEMZONE_NAMESIZE];

        snprintf(z_name, sizeof(z_name), "%s_%s_%d_%d",
                dev->driver->pci_drv.name, ring_name, dev->data->port_id,
                queue_id);

        if ((mz = rte_memzone_lookup(z_name)) != 0)
                return (mz);

#ifdef RTE_LIBRTE_XEN_DOM0
        return rte_memzone_reserve_bounded(z_name, ring_size,
                        socket_id, 0, CACHE_LINE_SIZE, RTE_PGSIZE_2M);
#else
        return rte_memzone_reserve(z_name, ring_size, socket_id, 0);
#endif
}

static void
em_tx_queue_release_mbufs(struct em_tx_queue *txq)
{
        unsigned i;

        if (txq->sw_ring != NULL) {
                for (i = 0; i != txq->nb_tx_desc; i++) {
                        if (txq->sw_ring[i].mbuf != NULL) {
                                rte_pktmbuf_free_seg(txq->sw_ring[i].mbuf);
                                txq->sw_ring[i].mbuf = NULL;
                        }
                }
        }
}

static void
em_tx_queue_release(struct em_tx_queue *txq)
{
        if (txq != NULL) {
                em_tx_queue_release_mbufs(txq);
                rte_free(txq->sw_ring);
                rte_free(txq);
        }
}

void
eth_em_tx_queue_release(void *txq)
{
        em_tx_queue_release(txq);
}

/* (Re)set dynamic em_tx_queue fields to defaults */
static void
em_reset_tx_queue(struct em_tx_queue *txq)
{
        uint16_t i, nb_desc, prev;
        static const struct e1000_data_desc txd_init = {
                .upper.fields = {.status = E1000_TXD_STAT_DD},
        };

        nb_desc = txq->nb_tx_desc;

        /* Initialize ring entries */

        prev = (uint16_t) (nb_desc - 1);

        for (i = 0; i < nb_desc; i++) {
                txq->tx_ring[i] = txd_init;
                txq->sw_ring[i].mbuf = NULL;
                txq->sw_ring[i].last_id = i;
                txq->sw_ring[prev].next_id = i;
                prev = i;
        }

        /*
         * Always allow 1 descriptor to be un-allocated to avoid
         * a H/W race condition
         */
        txq->nb_tx_free = (uint16_t)(nb_desc - 1);
        txq->last_desc_cleaned = (uint16_t)(nb_desc - 1);
        txq->nb_tx_used = 0;
        txq->tx_tail = 0;

        memset((void*)&txq->ctx_cache, 0, sizeof (txq->ctx_cache));
}

int
eth_em_tx_queue_setup(struct rte_eth_dev *dev,
                         uint16_t queue_idx,
                         uint16_t nb_desc,
                         unsigned int socket_id,
                         const struct rte_eth_txconf *tx_conf)
{
        const struct rte_memzone *tz;
        struct em_tx_queue *txq;
        struct e1000_hw     *hw;
        uint32_t tsize;
        uint16_t tx_rs_thresh, tx_free_thresh;

        hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);

        /*
         * Validate number of transmit descriptors.
         * It must not exceed hardware maximum, and must be multiple
         * of EM_ALIGN.
         */
        if (((nb_desc * sizeof(*txq->tx_ring)) % EM_ALIGN) != 0 ||
                        (nb_desc > EM_MAX_RING_DESC) ||
                        (nb_desc < EM_MIN_RING_DESC)) {
                return -(EINVAL);
        }

        tx_free_thresh = tx_conf->tx_free_thresh;
        if (tx_free_thresh == 0)
                tx_free_thresh = (uint16_t)RTE_MIN(nb_desc / 4,
                                        DEFAULT_TX_FREE_THRESH);

        tx_rs_thresh = tx_conf->tx_rs_thresh;
        if (tx_rs_thresh == 0)
                tx_rs_thresh = (uint16_t)RTE_MIN(tx_free_thresh,
                                        DEFAULT_TX_RS_THRESH);

        if (tx_free_thresh >= (nb_desc - 3)) {
                RTE_LOG(ERR, PMD, "tx_free_thresh must be less than the "
                        "number of TX descriptors minus 3. (tx_free_thresh=%u "
                        "port=%d queue=%d)\n", (unsigned int)tx_free_thresh,
                                (int)dev->data->port_id, (int)queue_idx);
                return -(EINVAL);
        }
        if (tx_rs_thresh > tx_free_thresh) {
                RTE_LOG(ERR, PMD, "tx_rs_thresh must be less than or equal to "
                        "tx_free_thresh. (tx_free_thresh=%u tx_rs_thresh=%u "
                        "port=%d queue=%d)\n", (unsigned int)tx_free_thresh,
                        (unsigned int)tx_rs_thresh, (int)dev->data->port_id,
                                                        (int)queue_idx);
                return -(EINVAL);
        }

        /*
         * If rs_bit_thresh is greater than 1, then TX WTHRESH should be
         * set to 0. If WTHRESH is greater than zero, the RS bit is ignored
         * by the NIC and all descriptors are written back after the NIC
         * accumulates WTHRESH descriptors.
         */
        if (tx_conf->tx_thresh.wthresh != 0 && tx_rs_thresh != 1) {
                RTE_LOG(ERR, PMD, "TX WTHRESH must be set to 0 if "
                        "tx_rs_thresh is greater than 1. (tx_rs_thresh=%u "
                        "port=%d queue=%d)\n", (unsigned int)tx_rs_thresh,
                                (int)dev->data->port_id, (int)queue_idx);
                return -(EINVAL);
        }

        /* Free memory prior to re-allocation if needed... */
        if (dev->data->tx_queues[queue_idx] != NULL) {
                em_tx_queue_release(dev->data->tx_queues[queue_idx]);
                dev->data->tx_queues[queue_idx] = NULL;
        }

        /*
         * Allocate TX ring hardware descriptors. A memzone large enough to
         * handle the maximum ring size is allocated in order to allow for
         * resizing in later calls to the queue setup function.
         */
        tsize = sizeof (txq->tx_ring[0]) * EM_MAX_RING_DESC;
        if ((tz = ring_dma_zone_reserve(dev, "tx_ring", queue_idx, tsize,
                        socket_id)) == NULL)
                return (-ENOMEM);

        /* Allocate the tx queue data structure. */
        if ((txq = rte_zmalloc("ethdev TX queue", sizeof(*txq),
                        CACHE_LINE_SIZE)) == NULL)
                return (-ENOMEM);

        /* Allocate software ring */
        if ((txq->sw_ring = rte_zmalloc("txq->sw_ring",
                        sizeof(txq->sw_ring[0]) * nb_desc,
                        CACHE_LINE_SIZE)) == NULL) {
                em_tx_queue_release(txq);
                return (-ENOMEM);
        }

        txq->nb_tx_desc = nb_desc;
        txq->tx_free_thresh = tx_free_thresh;
        txq->tx_rs_thresh = tx_rs_thresh;
        txq->pthresh = tx_conf->tx_thresh.pthresh;
        txq->hthresh = tx_conf->tx_thresh.hthresh;
        txq->wthresh = tx_conf->tx_thresh.wthresh;
        txq->queue_id = queue_idx;
        txq->port_id = dev->data->port_id;

        txq->tdt_reg_addr = E1000_PCI_REG_ADDR(hw, E1000_TDT(queue_idx));
#ifndef RTE_LIBRTE_XEN_DOM0
        txq->tx_ring_phys_addr = (uint64_t) tz->phys_addr;
#else
        txq->tx_ring_phys_addr = rte_mem_phy2mch(tz->memseg_id, tz->phys_addr);
#endif
        txq->tx_ring = (struct e1000_data_desc *) tz->addr;

        PMD_INIT_LOG(DEBUG, "sw_ring=%p hw_ring=%p dma_addr=0x%"PRIx64"\n",
                txq->sw_ring, txq->tx_ring, txq->tx_ring_phys_addr);

        em_reset_tx_queue(txq);

        dev->data->tx_queues[queue_idx] = txq;
        return (0);
}

static void
em_rx_queue_release_mbufs(struct em_rx_queue *rxq)
{
        unsigned i;

        if (rxq->sw_ring != NULL) {
                for (i = 0; i != rxq->nb_rx_desc; i++) {
                        if (rxq->sw_ring[i].mbuf != NULL) {
                                rte_pktmbuf_free_seg(rxq->sw_ring[i].mbuf);
                                rxq->sw_ring[i].mbuf = NULL;
                        }
                }
        }
}

static void
em_rx_queue_release(struct em_rx_queue *rxq)
{
        if (rxq != NULL) {
                em_rx_queue_release_mbufs(rxq);
                rte_free(rxq->sw_ring);
                rte_free(rxq);
        }
}

void
eth_em_rx_queue_release(void *rxq)
{
        em_rx_queue_release(rxq);
}

/* Reset dynamic em_rx_queue fields back to defaults */
static void
em_reset_rx_queue(struct em_rx_queue *rxq)
{
        rxq->rx_tail = 0;
        rxq->nb_rx_hold = 0;
        rxq->pkt_first_seg = NULL;
        rxq->pkt_last_seg = NULL;
}

int
eth_em_rx_queue_setup(struct rte_eth_dev *dev,
                uint16_t queue_idx,
                uint16_t nb_desc,
                unsigned int socket_id,
                const struct rte_eth_rxconf *rx_conf,
                struct rte_mempool *mp)
{
        const struct rte_memzone *rz;
        struct em_rx_queue *rxq;
        struct e1000_hw     *hw;
        uint32_t rsize;

        hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);

        /*
         * Validate number of receive descriptors.
         * It must not exceed hardware maximum, and must be multiple
         * of EM_ALIGN.
         */
        if (((nb_desc * sizeof(rxq->rx_ring[0])) % EM_ALIGN) != 0 ||
                        (nb_desc > EM_MAX_RING_DESC) ||
                        (nb_desc < EM_MIN_RING_DESC)) {
                return (-EINVAL);
        }

        /*
         * EM devices don't support drop_en functionality
         */
        if (rx_conf->rx_drop_en) {
                RTE_LOG(ERR, PMD, "drop_en functionality not supported by device\n");
                return (-EINVAL);
        }

        /* Free memory prior to re-allocation if needed. */
        if (dev->data->rx_queues[queue_idx] != NULL) {
                em_rx_queue_release(dev->data->rx_queues[queue_idx]);
                dev->data->rx_queues[queue_idx] = NULL;
        }

        /* Allocate RX ring for max possible mumber of hardware descriptors. */
        rsize = sizeof (rxq->rx_ring[0]) * EM_MAX_RING_DESC;
        if ((rz = ring_dma_zone_reserve(dev, "rx_ring", queue_idx, rsize,
                        socket_id)) == NULL)
                return (-ENOMEM);

        /* Allocate the RX queue data structure. */
        if ((rxq = rte_zmalloc("ethdev RX queue", sizeof(*rxq),
                        CACHE_LINE_SIZE)) == NULL)
                return (-ENOMEM);

        /* Allocate software ring. */
        if ((rxq->sw_ring = rte_zmalloc("rxq->sw_ring",
                        sizeof (rxq->sw_ring[0]) * nb_desc,
                        CACHE_LINE_SIZE)) == NULL) {
                em_rx_queue_release(rxq);
                return (-ENOMEM);
        }

        rxq->mb_pool = mp;
        rxq->nb_rx_desc = nb_desc;
        rxq->pthresh = rx_conf->rx_thresh.pthresh;
        rxq->hthresh = rx_conf->rx_thresh.hthresh;
        rxq->wthresh = rx_conf->rx_thresh.wthresh;
        rxq->rx_free_thresh = rx_conf->rx_free_thresh;
        rxq->queue_id = queue_idx;
        rxq->port_id = dev->data->port_id;
        rxq->crc_len = (uint8_t) ((dev->data->dev_conf.rxmode.hw_strip_crc) ?
                                0 : ETHER_CRC_LEN);

        rxq->rdt_reg_addr = E1000_PCI_REG_ADDR(hw, E1000_RDT(queue_idx));
        rxq->rdh_reg_addr = E1000_PCI_REG_ADDR(hw, E1000_RDH(queue_idx));
#ifndef RTE_LIBRTE_XEN_DOM0
        rxq->rx_ring_phys_addr = (uint64_t) rz->phys_addr;
#else
        rxq->rx_ring_phys_addr = rte_mem_phy2mch(rz->memseg_id, rz->phys_addr);
#endif
        rxq->rx_ring = (struct e1000_rx_desc *) rz->addr;

        PMD_INIT_LOG(DEBUG, "sw_ring=%p hw_ring=%p dma_addr=0x%"PRIx64"\n",
                rxq->sw_ring, rxq->rx_ring, rxq->rx_ring_phys_addr);

        dev->data->rx_queues[queue_idx] = rxq;
        em_reset_rx_queue(rxq);

        return (0);
}

uint32_t
eth_em_rx_queue_count(struct rte_eth_dev *dev, uint16_t rx_queue_id)
{
#define EM_RXQ_SCAN_INTERVAL 4
        volatile struct e1000_rx_desc *rxdp;
        struct em_rx_queue *rxq;
        uint32_t desc = 0;

        if (rx_queue_id >= dev->data->nb_rx_queues) {
                PMD_RX_LOG(DEBUG,"Invalid RX queue_id=%d\n", rx_queue_id);
                return 0;
        }

        rxq = dev->data->rx_queues[rx_queue_id];
        rxdp = &(rxq->rx_ring[rxq->rx_tail]);

        while ((desc < rxq->nb_rx_desc) &&
                (rxdp->status & E1000_RXD_STAT_DD)) {
                desc += EM_RXQ_SCAN_INTERVAL;
                rxdp += EM_RXQ_SCAN_INTERVAL;
                if (rxq->rx_tail + desc >= rxq->nb_rx_desc)
                        rxdp = &(rxq->rx_ring[rxq->rx_tail +
                                desc - rxq->nb_rx_desc]);
        }

        return desc;
}

int
eth_em_rx_descriptor_done(void *rx_queue, uint16_t offset)
{
        volatile struct e1000_rx_desc *rxdp;
        struct em_rx_queue *rxq = rx_queue;
        uint32_t desc;

        if (unlikely(offset >= rxq->nb_rx_desc))
                return 0;
        desc = rxq->rx_tail + offset;
        if (desc >= rxq->nb_rx_desc)
                desc -= rxq->nb_rx_desc;

        rxdp = &rxq->rx_ring[desc];
        return !!(rxdp->status & E1000_RXD_STAT_DD);
}

void
em_dev_clear_queues(struct rte_eth_dev *dev)
{
        uint16_t i;
        struct em_tx_queue *txq;
        struct em_rx_queue *rxq;

        for (i = 0; i < dev->data->nb_tx_queues; i++) {
                txq = dev->data->tx_queues[i];
                if (txq != NULL) {
                        em_tx_queue_release_mbufs(txq);
                        em_reset_tx_queue(txq);
                }
        }

        for (i = 0; i < dev->data->nb_rx_queues; i++) {
                rxq = dev->data->rx_queues[i];
                if (rxq != NULL) {
                        em_rx_queue_release_mbufs(rxq);
                        em_reset_rx_queue(rxq);
                }
        }
}

/*
 * Takes as input/output parameter RX buffer size.
 * Returns (BSIZE | BSEX | FLXBUF) fields of RCTL register.
 */
static uint32_t
em_rctl_bsize(__rte_unused enum e1000_mac_type hwtyp, uint32_t *bufsz)
{
        /*
         * For BSIZE & BSEX all configurable sizes are:
         * 16384: rctl |= (E1000_RCTL_SZ_16384 | E1000_RCTL_BSEX);
         *  8192: rctl |= (E1000_RCTL_SZ_8192  | E1000_RCTL_BSEX);
         *  4096: rctl |= (E1000_RCTL_SZ_4096  | E1000_RCTL_BSEX);
         *  2048: rctl |= E1000_RCTL_SZ_2048;
         *  1024: rctl |= E1000_RCTL_SZ_1024;
         *   512: rctl |= E1000_RCTL_SZ_512;
         *   256: rctl |= E1000_RCTL_SZ_256;
         */
        static const struct {
                uint32_t bufsz;
                uint32_t rctl;
        } bufsz_to_rctl[] = {
                {16384, (E1000_RCTL_SZ_16384 | E1000_RCTL_BSEX)},
                {8192,  (E1000_RCTL_SZ_8192  | E1000_RCTL_BSEX)},
                {4096,  (E1000_RCTL_SZ_4096  | E1000_RCTL_BSEX)},
                {2048,  E1000_RCTL_SZ_2048},
                {1024,  E1000_RCTL_SZ_1024},
                {512,   E1000_RCTL_SZ_512},
                {256,   E1000_RCTL_SZ_256},
        };

        int i;
        uint32_t rctl_bsize;

        rctl_bsize = *bufsz;

        /*
         * Starting from 82571 it is possible to specify RX buffer size
         * by RCTL.FLXBUF. When this field is different from zero, the
         * RX buffer size = RCTL.FLXBUF * 1K
         * (e.g. t is possible to specify RX buffer size  1,2,...,15KB).
         * It is working ok on real HW, but by some reason doesn't work
         * on VMware emulated 82574L.
         * So for now, always use BSIZE/BSEX to setup RX buffer size.
         * If you don't plan to use it on VMware emulated 82574L and
         * would like to specify RX buffer size in 1K granularity,
         * uncomment the following lines:
         * ***************************************************************
         * if (hwtyp >= e1000_82571 && hwtyp <= e1000_82574 &&
         *              rctl_bsize >= EM_RCTL_FLXBUF_STEP) {
         *      rctl_bsize /= EM_RCTL_FLXBUF_STEP;
         *      *bufsz = rctl_bsize;
         *      return (rctl_bsize << E1000_RCTL_FLXBUF_SHIFT &
         *              E1000_RCTL_FLXBUF_MASK);
         * }
         * ***************************************************************
         */

        for (i = 0; i != sizeof(bufsz_to_rctl) / sizeof(bufsz_to_rctl[0]);
                        i++) {
                if (rctl_bsize >= bufsz_to_rctl[i].bufsz) {
                        *bufsz = bufsz_to_rctl[i].bufsz;
                        return (bufsz_to_rctl[i].rctl);
                }
        }

        /* Should never happen. */
        return (-EINVAL);
}

static int
em_alloc_rx_queue_mbufs(struct em_rx_queue *rxq)
{
        struct em_rx_entry *rxe = rxq->sw_ring;
        uint64_t dma_addr;
        unsigned i;
        static const struct e1000_rx_desc rxd_init = {
                .buffer_addr = 0,
        };

        /* Initialize software ring entries */
        for (i = 0; i < rxq->nb_rx_desc; i++) {
                volatile struct e1000_rx_desc *rxd;
                struct rte_mbuf *mbuf = rte_rxmbuf_alloc(rxq->mb_pool);

                if (mbuf == NULL) {
                        PMD_INIT_LOG(ERR, "RX mbuf alloc failed "
                                "queue_id=%hu\n", rxq->queue_id);
                        return (-ENOMEM);
                }

                dma_addr = rte_cpu_to_le_64(RTE_MBUF_DATA_DMA_ADDR_DEFAULT(mbuf));

                /* Clear HW ring memory */
                rxq->rx_ring[i] = rxd_init;

                rxd = &rxq->rx_ring[i];
                rxd->buffer_addr = dma_addr;
                rxe[i].mbuf = mbuf;
        }

        return 0;
}

/*********************************************************************
 *
 *  Enable receive unit.
 *
 **********************************************************************/
int
eth_em_rx_init(struct rte_eth_dev *dev)
{
        struct e1000_hw *hw;
        struct em_rx_queue *rxq;
        uint32_t rctl;
        uint32_t rfctl;
        uint32_t rxcsum;
        uint32_t rctl_bsize;
        uint16_t i;
        int ret;

        hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);

        /*
         * Make sure receives are disabled while setting
         * up the descriptor ring.
         */
        rctl = E1000_READ_REG(hw, E1000_RCTL);
        E1000_WRITE_REG(hw, E1000_RCTL, rctl & ~E1000_RCTL_EN);

        rfctl = E1000_READ_REG(hw, E1000_RFCTL);

        /* Disable extended descriptor type. */
        rfctl &= ~E1000_RFCTL_EXTEN;
        /* Disable accelerated acknowledge */
        if (hw->mac.type == e1000_82574)
                rfctl |= E1000_RFCTL_ACK_DIS;

        E1000_WRITE_REG(hw, E1000_RFCTL, rfctl);

        /*
         * XXX TEMPORARY WORKAROUND: on some systems with 82573
         * long latencies are observed, like Lenovo X60. This
         * change eliminates the problem, but since having positive
         * values in RDTR is a known source of problems on other
         * platforms another solution is being sought.
         */
        if (hw->mac.type == e1000_82573)
                E1000_WRITE_REG(hw, E1000_RDTR, 0x20);

        dev->rx_pkt_burst = (eth_rx_burst_t)eth_em_recv_pkts;

        /* Determine RX bufsize. */
        rctl_bsize = EM_MAX_BUF_SIZE;
        for (i = 0; i < dev->data->nb_rx_queues; i++) {
                struct rte_pktmbuf_pool_private *mbp_priv;
                uint32_t buf_size;

                rxq = dev->data->rx_queues[i];
                mbp_priv = rte_mempool_get_priv(rxq->mb_pool);
                buf_size = mbp_priv->mbuf_data_room_size - RTE_PKTMBUF_HEADROOM;
                rctl_bsize = RTE_MIN(rctl_bsize, buf_size);
        }

        rctl |= em_rctl_bsize(hw->mac.type, &rctl_bsize);

        /* Configure and enable each RX queue. */
        for (i = 0; i < dev->data->nb_rx_queues; i++) {
                uint64_t bus_addr;
                uint32_t rxdctl;

                rxq = dev->data->rx_queues[i];

                /* Allocate buffers for descriptor rings and setup queue */
                ret = em_alloc_rx_queue_mbufs(rxq);
                if (ret)
                        return ret;

                /*
                 * Reset crc_len in case it was changed after queue setup by a
                 *  call to configure
                 */
                rxq->crc_len =
                        (uint8_t)(dev->data->dev_conf.rxmode.hw_strip_crc ?
                                                        0 : ETHER_CRC_LEN);

                bus_addr = rxq->rx_ring_phys_addr;
                E1000_WRITE_REG(hw, E1000_RDLEN(i),
                                rxq->nb_rx_desc *
                                sizeof(*rxq->rx_ring));
                E1000_WRITE_REG(hw, E1000_RDBAH(i),
                                (uint32_t)(bus_addr >> 32));
                E1000_WRITE_REG(hw, E1000_RDBAL(i), (uint32_t)bus_addr);

                E1000_WRITE_REG(hw, E1000_RDH(i), 0);
                E1000_WRITE_REG(hw, E1000_RDT(i), rxq->nb_rx_desc - 1);

                rxdctl = E1000_READ_REG(hw, E1000_RXDCTL(0));
                rxdctl &= 0xFE000000;
                rxdctl |= rxq->pthresh & 0x3F;
                rxdctl |= (rxq->hthresh & 0x3F) << 8;
                rxdctl |= (rxq->wthresh & 0x3F) << 16;
                rxdctl |= E1000_RXDCTL_GRAN;
                E1000_WRITE_REG(hw, E1000_RXDCTL(i), rxdctl);

                /*
                 * Due to EM devices not having any sort of hardware
                 * limit for packet length, jumbo frame of any size
                 * can be accepted, thus we have to enable scattered
                 * rx if jumbo frames are enabled (or if buffer size
                 * is too small to accommodate non-jumbo packets)
                 * to avoid splitting packets that don't fit into
                 * one buffer.
                 */
                if (dev->data->dev_conf.rxmode.jumbo_frame ||
                                rctl_bsize < ETHER_MAX_LEN) {
                        dev->rx_pkt_burst =
                                (eth_rx_burst_t)eth_em_recv_scattered_pkts;
                        dev->data->scattered_rx = 1;
                }
        }

        if (dev->data->dev_conf.rxmode.enable_scatter) {
                dev->rx_pkt_burst = eth_em_recv_scattered_pkts;
                dev->data->scattered_rx = 1;
        }

        /*
         * Setup the Checksum Register.
         * Receive Full-Packet Checksum Offload is mutually exclusive with RSS.
         */
        rxcsum = E1000_READ_REG(hw, E1000_RXCSUM);

        if (dev->data->dev_conf.rxmode.hw_ip_checksum)
                rxcsum |= E1000_RXCSUM_IPOFL;
        else
                rxcsum &= ~E1000_RXCSUM_IPOFL;
        E1000_WRITE_REG(hw, E1000_RXCSUM, rxcsum);

        /* No MRQ or RSS support for now */

        /* Set early receive threshold on appropriate hw */
        if ((hw->mac.type == e1000_ich9lan ||
                        hw->mac.type == e1000_pch2lan ||
                        hw->mac.type == e1000_ich10lan) &&
                        dev->data->dev_conf.rxmode.jumbo_frame == 1) {
                u32 rxdctl = E1000_READ_REG(hw, E1000_RXDCTL(0));
                E1000_WRITE_REG(hw, E1000_RXDCTL(0), rxdctl | 3);
                E1000_WRITE_REG(hw, E1000_ERT, 0x100 | (1 << 13));
        }

        if (hw->mac.type == e1000_pch2lan) {
                if (dev->data->dev_conf.rxmode.jumbo_frame == 1)
                        e1000_lv_jumbo_workaround_ich8lan(hw, TRUE);
                else
                        e1000_lv_jumbo_workaround_ich8lan(hw, FALSE);
        }

        /* Setup the Receive Control Register. */
        if (dev->data->dev_conf.rxmode.hw_strip_crc)
                rctl |= E1000_RCTL_SECRC; /* Strip Ethernet CRC. */
        else
                rctl &= ~E1000_RCTL_SECRC; /* Do not Strip Ethernet CRC. */

        rctl &= ~(3 << E1000_RCTL_MO_SHIFT);
        rctl |= E1000_RCTL_EN | E1000_RCTL_BAM | E1000_RCTL_LBM_NO |
                E1000_RCTL_RDMTS_HALF |
                (hw->mac.mc_filter_type << E1000_RCTL_MO_SHIFT);

        /* Make sure VLAN Filters are off. */
        rctl &= ~E1000_RCTL_VFE;
        /* Don't store bad packets. */
        rctl &= ~E1000_RCTL_SBP;
        /* Legacy descriptor type. */
        rctl &= ~E1000_RCTL_DTYP_MASK;

        /*
         * Configure support of jumbo frames, if any.
         */
        if (dev->data->dev_conf.rxmode.jumbo_frame == 1)
                rctl |= E1000_RCTL_LPE;
        else
                rctl &= ~E1000_RCTL_LPE;

        /* Enable Receives. */
        E1000_WRITE_REG(hw, E1000_RCTL, rctl);

        return 0;
}

/*********************************************************************
 *
 *  Enable transmit unit.
 *
 **********************************************************************/
void
eth_em_tx_init(struct rte_eth_dev *dev)
{
        struct e1000_hw     *hw;
        struct em_tx_queue *txq;
        uint32_t tctl;
        uint32_t txdctl;
        uint16_t i;

        hw = E1000_DEV_PRIVATE_TO_HW(dev->data->dev_private);

        /* Setup the Base and Length of the Tx Descriptor Rings. */
        for (i = 0; i < dev->data->nb_tx_queues; i++) {
                uint64_t bus_addr;

                txq = dev->data->tx_queues[i];
                bus_addr = txq->tx_ring_phys_addr;
                E1000_WRITE_REG(hw, E1000_TDLEN(i),
                                txq->nb_tx_desc *
                                sizeof(*txq->tx_ring));
                E1000_WRITE_REG(hw, E1000_TDBAH(i),
                                (uint32_t)(bus_addr >> 32));
                E1000_WRITE_REG(hw, E1000_TDBAL(i), (uint32_t)bus_addr);

                /* Setup the HW Tx Head and Tail descriptor pointers. */
                E1000_WRITE_REG(hw, E1000_TDT(i), 0);
                E1000_WRITE_REG(hw, E1000_TDH(i), 0);

                /* Setup Transmit threshold registers. */
                txdctl = E1000_READ_REG(hw, E1000_TXDCTL(i));
                /*
                 * bit 22 is reserved, on some models should always be 0,
                 * on others  - always 1.
                 */
                txdctl &= E1000_TXDCTL_COUNT_DESC;
                txdctl |= txq->pthresh & 0x3F;
                txdctl |= (txq->hthresh & 0x3F) << 8;
                txdctl |= (txq->wthresh & 0x3F) << 16;
                txdctl |= E1000_TXDCTL_GRAN;
                E1000_WRITE_REG(hw, E1000_TXDCTL(i), txdctl);
        }

        /* Program the Transmit Control Register. */
        tctl = E1000_READ_REG(hw, E1000_TCTL);
        tctl &= ~E1000_TCTL_CT;
        tctl |= (E1000_TCTL_PSP | E1000_TCTL_RTLC | E1000_TCTL_EN |
                 (E1000_COLLISION_THRESHOLD << E1000_CT_SHIFT));

        /* This write will effectively turn on the transmit unit. */
        E1000_WRITE_REG(hw, E1000_TCTL, tctl);
}