freebsd-skq/sys/dev/sfxge/sfxge_tx.c

/*-
 * Copyright (c) 2010-2015 Solarflare Communications Inc.
 * All rights reserved.
 *
 * This software was developed in part by Philip Paeps under contract for
 * Solarflare Communications, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * 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.
 *
 * The views and conclusions contained in the software and documentation are
 * those of the authors and should not be interpreted as representing official
 * policies, either expressed or implied, of the FreeBSD Project.
 */

/* Theory of operation:
 *
 * Tx queues allocation and mapping
 *
 * One Tx queue with enabled checksum offload is allocated per Rx channel
 * (event queue).  Also 2 Tx queues (one without checksum offload and one
 * with IP checksum offload only) are allocated and bound to event queue 0.
 * sfxge_txq_type is used as Tx queue label.
 *
 * So, event queue plus label mapping to Tx queue index is:
 *	if event queue index is 0, TxQ-index = TxQ-label * [0..SFXGE_TXQ_NTYPES)
 *	else TxQ-index = SFXGE_TXQ_NTYPES + EvQ-index - 1
 * See sfxge_get_txq_by_label() sfxge_ev.c
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/smp.h>
#include <sys/socket.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/limits.h>

#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/if_vlan_var.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/tcp.h>

#include "common/efx.h"

#include "sfxge.h"
#include "sfxge_tx.h"


#define	SFXGE_PARAM_TX_DPL_GET_MAX	SFXGE_PARAM(tx_dpl_get_max)
static int sfxge_tx_dpl_get_max = SFXGE_TX_DPL_GET_PKT_LIMIT_DEFAULT;
TUNABLE_INT(SFXGE_PARAM_TX_DPL_GET_MAX, &sfxge_tx_dpl_get_max);
SYSCTL_INT(_hw_sfxge, OID_AUTO, tx_dpl_get_max, CTLFLAG_RDTUN,
	   &sfxge_tx_dpl_get_max, 0,
	   "Maximum number of any packets in deferred packet get-list");

#define	SFXGE_PARAM_TX_DPL_GET_NON_TCP_MAX \
	SFXGE_PARAM(tx_dpl_get_non_tcp_max)
static int sfxge_tx_dpl_get_non_tcp_max =
	SFXGE_TX_DPL_GET_NON_TCP_PKT_LIMIT_DEFAULT;
TUNABLE_INT(SFXGE_PARAM_TX_DPL_GET_NON_TCP_MAX, &sfxge_tx_dpl_get_non_tcp_max);
SYSCTL_INT(_hw_sfxge, OID_AUTO, tx_dpl_get_non_tcp_max, CTLFLAG_RDTUN,
	   &sfxge_tx_dpl_get_non_tcp_max, 0,
	   "Maximum number of non-TCP packets in deferred packet get-list");

#define	SFXGE_PARAM_TX_DPL_PUT_MAX	SFXGE_PARAM(tx_dpl_put_max)
static int sfxge_tx_dpl_put_max = SFXGE_TX_DPL_PUT_PKT_LIMIT_DEFAULT;
TUNABLE_INT(SFXGE_PARAM_TX_DPL_PUT_MAX, &sfxge_tx_dpl_put_max);
SYSCTL_INT(_hw_sfxge, OID_AUTO, tx_dpl_put_max, CTLFLAG_RDTUN,
	   &sfxge_tx_dpl_put_max, 0,
	   "Maximum number of any packets in deferred packet put-list");

#define	SFXGE_PARAM_TSO_FW_ASSISTED	SFXGE_PARAM(tso_fw_assisted)
static int sfxge_tso_fw_assisted = (SFXGE_FATSOV1 | SFXGE_FATSOV2);
TUNABLE_INT(SFXGE_PARAM_TSO_FW_ASSISTED, &sfxge_tso_fw_assisted);
SYSCTL_INT(_hw_sfxge, OID_AUTO, tso_fw_assisted, CTLFLAG_RDTUN,
	   &sfxge_tso_fw_assisted, 0,
	   "Bitmask of FW-assisted TSO allowed to use if supported by NIC firmware");


static const struct {
	const char *name;
	size_t offset;
} sfxge_tx_stats[] = {
#define	SFXGE_TX_STAT(name, member) \
	{ #name, offsetof(struct sfxge_txq, member) }
	SFXGE_TX_STAT(tso_bursts, tso_bursts),
	SFXGE_TX_STAT(tso_packets, tso_packets),
	SFXGE_TX_STAT(tso_long_headers, tso_long_headers),
	SFXGE_TX_STAT(tso_pdrop_too_many, tso_pdrop_too_many),
	SFXGE_TX_STAT(tso_pdrop_no_rsrc, tso_pdrop_no_rsrc),
	SFXGE_TX_STAT(tx_collapses, collapses),
	SFXGE_TX_STAT(tx_drops, drops),
	SFXGE_TX_STAT(tx_get_overflow, get_overflow),
	SFXGE_TX_STAT(tx_get_non_tcp_overflow, get_non_tcp_overflow),
	SFXGE_TX_STAT(tx_put_overflow, put_overflow),
	SFXGE_TX_STAT(tx_netdown_drops, netdown_drops),
};


/* Forward declarations. */
static void sfxge_tx_qdpl_service(struct sfxge_txq *txq);
static void sfxge_tx_qlist_post(struct sfxge_txq *txq);
static void sfxge_tx_qunblock(struct sfxge_txq *txq);
static int sfxge_tx_queue_tso(struct sfxge_txq *txq, struct mbuf *mbuf,
			      const bus_dma_segment_t *dma_seg, int n_dma_seg,
			      int vlan_tagged);

static int
sfxge_tx_maybe_insert_tag(struct sfxge_txq *txq, struct mbuf *mbuf)
{
	uint16_t this_tag = ((mbuf->m_flags & M_VLANTAG) ?
			     mbuf->m_pkthdr.ether_vtag :
			     0);

	if (this_tag == txq->hw_vlan_tci)
		return (0);

	efx_tx_qdesc_vlantci_create(txq->common,
				    bswap16(this_tag),
				    &txq->pend_desc[0]);
	txq->n_pend_desc = 1;
	txq->hw_vlan_tci = this_tag;
	return (1);
}

static inline void
sfxge_next_stmp(struct sfxge_txq *txq, struct sfxge_tx_mapping **pstmp)
{
	KASSERT((*pstmp)->flags == 0, ("stmp flags are not 0"));
	if (__predict_false(*pstmp ==
			    &txq->stmp[txq->ptr_mask]))
		*pstmp = &txq->stmp[0];
	else
		(*pstmp)++;
}


void
sfxge_tx_qcomplete(struct sfxge_txq *txq, struct sfxge_evq *evq)
{
	unsigned int completed;

	SFXGE_EVQ_LOCK_ASSERT_OWNED(evq);

	completed = txq->completed;
	while (completed != txq->pending) {
		struct sfxge_tx_mapping *stmp;
		unsigned int id;

		id = completed++ & txq->ptr_mask;

		stmp = &txq->stmp[id];
		if (stmp->flags & TX_BUF_UNMAP) {
			bus_dmamap_unload(txq->packet_dma_tag, stmp->map);
			if (stmp->flags & TX_BUF_MBUF) {
				struct mbuf *m = stmp->u.mbuf;
				do
					m = m_free(m);
				while (m != NULL);
			} else {
				free(stmp->u.heap_buf, M_SFXGE);
			}
			stmp->flags = 0;
		}
	}
	txq->completed = completed;

	/* Check whether we need to unblock the queue. */
	mb();
	if (txq->blocked) {
		unsigned int level;

		level = txq->added - txq->completed;
		if (level <= SFXGE_TXQ_UNBLOCK_LEVEL(txq->entries))
			sfxge_tx_qunblock(txq);
	}
}

static unsigned int
sfxge_is_mbuf_non_tcp(struct mbuf *mbuf)
{
	/* Absence of TCP checksum flags does not mean that it is non-TCP
	 * but it should be true if user wants to achieve high throughput.
	 */
	return (!(mbuf->m_pkthdr.csum_flags & (CSUM_IP_TCP | CSUM_IP6_TCP)));
}

/*
 * Reorder the put list and append it to the get list.
 */
static void
sfxge_tx_qdpl_swizzle(struct sfxge_txq *txq)
{
	struct sfxge_tx_dpl *stdp;
	struct mbuf *mbuf, *get_next, **get_tailp;
	volatile uintptr_t *putp;
	uintptr_t put;
	unsigned int count;
	unsigned int non_tcp_count;

	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	stdp = &txq->dpl;

	/* Acquire the put list. */
	putp = &stdp->std_put;
	put = atomic_readandclear_ptr(putp);
	mbuf = (void *)put;

	if (mbuf == NULL)
		return;

	/* Reverse the put list. */
	get_tailp = &mbuf->m_nextpkt;
	get_next = NULL;

	count = 0;
	non_tcp_count = 0;
	do {
		struct mbuf *put_next;

		non_tcp_count += sfxge_is_mbuf_non_tcp(mbuf);
		put_next = mbuf->m_nextpkt;
		mbuf->m_nextpkt = get_next;
		get_next = mbuf;
		mbuf = put_next;

		count++;
	} while (mbuf != NULL);

	if (count > stdp->std_put_hiwat)
		stdp->std_put_hiwat = count;

	/* Append the reversed put list to the get list. */
	KASSERT(*get_tailp == NULL, ("*get_tailp != NULL"));
	*stdp->std_getp = get_next;
	stdp->std_getp = get_tailp;
	stdp->std_get_count += count;
	stdp->std_get_non_tcp_count += non_tcp_count;
}

static void
sfxge_tx_qreap(struct sfxge_txq *txq)
{
	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	txq->reaped = txq->completed;
}

static void
sfxge_tx_qlist_post(struct sfxge_txq *txq)
{
	unsigned int old_added;
	unsigned int block_level;
	unsigned int level;
	int rc;

	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	KASSERT(txq->n_pend_desc != 0, ("txq->n_pend_desc == 0"));
	KASSERT(txq->n_pend_desc <= txq->max_pkt_desc,
		("txq->n_pend_desc too large"));
	KASSERT(!txq->blocked, ("txq->blocked"));

	old_added = txq->added;

	/* Post the fragment list. */
	rc = efx_tx_qdesc_post(txq->common, txq->pend_desc, txq->n_pend_desc,
			  txq->reaped, &txq->added);
	KASSERT(rc == 0, ("efx_tx_qdesc_post() failed"));

	/* If efx_tx_qdesc_post() had to refragment, our information about
	 * buffers to free may be associated with the wrong
	 * descriptors.
	 */
	KASSERT(txq->added - old_added == txq->n_pend_desc,
		("efx_tx_qdesc_post() refragmented descriptors"));

	level = txq->added - txq->reaped;
	KASSERT(level <= txq->entries, ("overfilled TX queue"));

	/* Clear the fragment list. */
	txq->n_pend_desc = 0;

	/*
	 * Set the block level to ensure there is space to generate a
	 * large number of descriptors for TSO.
	 */
	block_level = EFX_TXQ_LIMIT(txq->entries) - txq->max_pkt_desc;

	/* Have we reached the block level? */
	if (level < block_level)
		return;

	/* Reap, and check again */
	sfxge_tx_qreap(txq);
	level = txq->added - txq->reaped;
	if (level < block_level)
		return;

	txq->blocked = 1;

	/*
	 * Avoid a race with completion interrupt handling that could leave
	 * the queue blocked.
	 */
	mb();
	sfxge_tx_qreap(txq);
	level = txq->added - txq->reaped;
	if (level < block_level) {
		mb();
		txq->blocked = 0;
	}
}

static int sfxge_tx_queue_mbuf(struct sfxge_txq *txq, struct mbuf *mbuf)
{
	bus_dmamap_t *used_map;
	bus_dmamap_t map;
	bus_dma_segment_t dma_seg[SFXGE_TX_MAPPING_MAX_SEG];
	unsigned int id;
	struct sfxge_tx_mapping *stmp;
	efx_desc_t *desc;
	int n_dma_seg;
	int rc;
	int i;
	int eop;
	int vlan_tagged;

	KASSERT(!txq->blocked, ("txq->blocked"));

	if (mbuf->m_pkthdr.csum_flags & CSUM_TSO)
		prefetch_read_many(mbuf->m_data);

	if (__predict_false(txq->init_state != SFXGE_TXQ_STARTED)) {
		rc = EINTR;
		goto reject;
	}

	/* Load the packet for DMA. */
	id = txq->added & txq->ptr_mask;
	stmp = &txq->stmp[id];
	rc = bus_dmamap_load_mbuf_sg(txq->packet_dma_tag, stmp->map,
				     mbuf, dma_seg, &n_dma_seg, 0);
	if (rc == EFBIG) {
		/* Try again. */
		struct mbuf *new_mbuf = m_collapse(mbuf, M_NOWAIT,
						   SFXGE_TX_MAPPING_MAX_SEG);
		if (new_mbuf == NULL)
			goto reject;
		++txq->collapses;
		mbuf = new_mbuf;
		rc = bus_dmamap_load_mbuf_sg(txq->packet_dma_tag,
					     stmp->map, mbuf,
					     dma_seg, &n_dma_seg, 0);
	}
	if (rc != 0)
		goto reject;

	/* Make the packet visible to the hardware. */
	bus_dmamap_sync(txq->packet_dma_tag, stmp->map, BUS_DMASYNC_PREWRITE);

	used_map = &stmp->map;

	vlan_tagged = sfxge_tx_maybe_insert_tag(txq, mbuf);
	if (vlan_tagged) {
		sfxge_next_stmp(txq, &stmp);
	}
	if (mbuf->m_pkthdr.csum_flags & CSUM_TSO) {
		rc = sfxge_tx_queue_tso(txq, mbuf, dma_seg, n_dma_seg, vlan_tagged);
		if (rc < 0)
			goto reject_mapped;
		stmp = &txq->stmp[(rc - 1) & txq->ptr_mask];
	} else {
		/* Add the mapping to the fragment list, and set flags
		 * for the buffer.
		 */

		i = 0;
		for (;;) {
			desc = &txq->pend_desc[i + vlan_tagged];
			eop = (i == n_dma_seg - 1);
			efx_tx_qdesc_dma_create(txq->common,
						dma_seg[i].ds_addr,
						dma_seg[i].ds_len,
						eop,
						desc);
			if (eop)
				break;
			i++;
			sfxge_next_stmp(txq, &stmp);
		}
		txq->n_pend_desc = n_dma_seg + vlan_tagged;
	}

	/*
	 * If the mapping required more than one descriptor
	 * then we need to associate the DMA map with the last
	 * descriptor, not the first.
	 */
	if (used_map != &stmp->map) {
		map = stmp->map;
		stmp->map = *used_map;
		*used_map = map;
	}

	stmp->u.mbuf = mbuf;
	stmp->flags = TX_BUF_UNMAP | TX_BUF_MBUF;

	/* Post the fragment list. */
	sfxge_tx_qlist_post(txq);

	return (0);

reject_mapped:
	bus_dmamap_unload(txq->packet_dma_tag, *used_map);
reject:
	/* Drop the packet on the floor. */
	m_freem(mbuf);
	++txq->drops;

	return (rc);
}

/*
 * Drain the deferred packet list into the transmit queue.
 */
static void
sfxge_tx_qdpl_drain(struct sfxge_txq *txq)
{
	struct sfxge_softc *sc;
	struct sfxge_tx_dpl *stdp;
	struct mbuf *mbuf, *next;
	unsigned int count;
	unsigned int non_tcp_count;
	unsigned int pushed;
	int rc;

	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	sc = txq->sc;
	stdp = &txq->dpl;
	pushed = txq->added;

	if (__predict_true(txq->init_state == SFXGE_TXQ_STARTED)) {
		prefetch_read_many(sc->enp);
		prefetch_read_many(txq->common);
	}

	mbuf = stdp->std_get;
	count = stdp->std_get_count;
	non_tcp_count = stdp->std_get_non_tcp_count;

	if (count > stdp->std_get_hiwat)
		stdp->std_get_hiwat = count;

	while (count != 0) {
		KASSERT(mbuf != NULL, ("mbuf == NULL"));

		next = mbuf->m_nextpkt;
		mbuf->m_nextpkt = NULL;

		ETHER_BPF_MTAP(sc->ifnet, mbuf); /* packet capture */

		if (next != NULL)
			prefetch_read_many(next);

		rc = sfxge_tx_queue_mbuf(txq, mbuf);
		--count;
		non_tcp_count -= sfxge_is_mbuf_non_tcp(mbuf);
		mbuf = next;
		if (rc != 0)
			continue;

		if (txq->blocked)
			break;

		/* Push the fragments to the hardware in batches. */
		if (txq->added - pushed >= SFXGE_TX_BATCH) {
			efx_tx_qpush(txq->common, txq->added, pushed);
			pushed = txq->added;
		}
	}

	if (count == 0) {
		KASSERT(mbuf == NULL, ("mbuf != NULL"));
		KASSERT(non_tcp_count == 0,
			("inconsistent TCP/non-TCP detection"));
		stdp->std_get = NULL;
		stdp->std_get_count = 0;
		stdp->std_get_non_tcp_count = 0;
		stdp->std_getp = &stdp->std_get;
	} else {
		stdp->std_get = mbuf;
		stdp->std_get_count = count;
		stdp->std_get_non_tcp_count = non_tcp_count;
	}

	if (txq->added != pushed)
		efx_tx_qpush(txq->common, txq->added, pushed);

	KASSERT(txq->blocked || stdp->std_get_count == 0,
		("queue unblocked but count is non-zero"));
}

#define	SFXGE_TX_QDPL_PENDING(_txq)	((_txq)->dpl.std_put != 0)

/*
 * Service the deferred packet list.
 *
 * NOTE: drops the txq mutex!
 */
static void
sfxge_tx_qdpl_service(struct sfxge_txq *txq)
{
	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	do {
		if (SFXGE_TX_QDPL_PENDING(txq))
			sfxge_tx_qdpl_swizzle(txq);

		if (!txq->blocked)
			sfxge_tx_qdpl_drain(txq);

		SFXGE_TXQ_UNLOCK(txq);
	} while (SFXGE_TX_QDPL_PENDING(txq) &&
		 SFXGE_TXQ_TRYLOCK(txq));
}

/*
 * Put a packet on the deferred packet get-list.
 */
static int
sfxge_tx_qdpl_put_locked(struct sfxge_txq *txq, struct mbuf *mbuf)
{
	struct sfxge_tx_dpl *stdp;

	stdp = &txq->dpl;

	KASSERT(mbuf->m_nextpkt == NULL, ("mbuf->m_nextpkt != NULL"));

	SFXGE_TXQ_LOCK_ASSERT_OWNED(txq);

	if (stdp->std_get_count >= stdp->std_get_max) {
		txq->get_overflow++;
		return (ENOBUFS);
	}
	if (sfxge_is_mbuf_non_tcp(mbuf)) {
		if (stdp->std_get_non_tcp_count >=
		    stdp->std_get_non_tcp_max) {
			txq->get_non_tcp_overflow++;
			return (ENOBUFS);
		}
		stdp->std_get_non_tcp_count++;
	}

	*(stdp->std_getp) = mbuf;
	stdp->std_getp = &mbuf->m_nextpkt;
	stdp->std_get_count++;

	return (0);
}

/*
 * Put a packet on the deferred packet put-list.
 *
 * We overload the csum_data field in the mbuf to keep track of this length
 * because there is no cheap alternative to avoid races.
 */
static int
sfxge_tx_qdpl_put_unlocked(struct sfxge_txq *txq, struct mbuf *mbuf)
{
	struct sfxge_tx_dpl *stdp;
	volatile uintptr_t *putp;
	uintptr_t old;
	uintptr_t new;
	unsigned old_len;

	KASSERT(mbuf->m_nextpkt == NULL, ("mbuf->m_nextpkt != NULL"));

	SFXGE_TXQ_LOCK_ASSERT_NOTOWNED(txq);

	stdp = &txq->dpl;
	putp = &stdp->std_put;
	new = (uintptr_t)mbuf;

	do {
		old = *putp;
		if (old != 0) {
			struct mbuf *mp = (struct mbuf *)old;
			old_len = mp->m_pkthdr.csum_data;
		} else
			old_len = 0;
		if (old_len >= stdp->std_put_max) {
			atomic_add_long(&txq->put_overflow, 1);
			return (ENOBUFS);
		}
		mbuf->m_pkthdr.csum_data = old_len + 1;
		mbuf->m_nextpkt = (void *)old;
	} while (atomic_cmpset_ptr(putp, old, new) == 0);

	return (0);
}

/*
 * Called from if_transmit - will try to grab the txq lock and enqueue to the
 * put list if it succeeds, otherwise try to push onto the defer list if space.
 */
static int
sfxge_tx_packet_add(struct sfxge_txq *txq, struct mbuf *m)
{
	int rc;

	if (!SFXGE_LINK_UP(txq->sc)) {
		atomic_add_long(&txq->netdown_drops, 1);
		return (ENETDOWN);
	}

	/*
	 * Try to grab the txq lock.  If we are able to get the lock,
	 * the packet will be appended to the "get list" of the deferred
	 * packet list.  Otherwise, it will be pushed on the "put list".
	 */
	if (SFXGE_TXQ_TRYLOCK(txq)) {
		/* First swizzle put-list to get-list to keep order */
		sfxge_tx_qdpl_swizzle(txq);

		rc = sfxge_tx_qdpl_put_locked(txq, m);

		/* Try to service the list. */
		sfxge_tx_qdpl_service(txq);
		/* Lock has been dropped. */
	} else {
		rc = sfxge_tx_qdpl_put_unlocked(txq, m);

		/*
		 * Try to grab the lock again.
		 *
		 * If we are able to get the lock, we need to process
		 * the deferred packet list.  If we are not able to get
		 * the lock, another thread is processing the list.
		 */
		if ((rc == 0) && SFXGE_TXQ_TRYLOCK(txq)) {
			sfxge_tx_qdpl_service(txq);
			/* Lock has been dropped. */
		}
	}

	SFXGE_TXQ_LOCK_ASSERT_NOTOWNED(txq);

	return (rc);
}

static void
sfxge_tx_qdpl_flush(struct sfxge_txq *txq)
{
	struct sfxge_tx_dpl *stdp = &txq->dpl;
	struct mbuf *mbuf, *next;

	SFXGE_TXQ_LOCK(txq);

	sfxge_tx_qdpl_swizzle(txq);
	for (mbuf = stdp->std_get; mbuf != NULL; mbuf = next) {
		next = mbuf->m_nextpkt;
		m_freem(mbuf);
	}
	stdp->std_get = NULL;
	stdp->std_get_count = 0;
	stdp->std_get_non_tcp_count = 0;
	stdp->std_getp = &stdp->std_get;

	SFXGE_TXQ_UNLOCK(txq);
}

void
sfxge_if_qflush(struct ifnet *ifp)
{
	struct sfxge_softc *sc;
	unsigned int i;

	sc = ifp->if_softc;

	for (i = 0; i < sc->txq_count; i++)
		sfxge_tx_qdpl_flush(sc->txq[i]);
}

#if SFXGE_TX_PARSE_EARLY

/* There is little space for user data in mbuf pkthdr, so we
 * use l*hlen fields which are not used by the driver otherwise
 * to store header offsets.
 * The fields are 8-bit, but it's ok, no header may be longer than 255 bytes.
 */


#define TSO_MBUF_PROTO(_mbuf)    ((_mbuf)->m_pkthdr.PH_loc.sixteen[0])
/* We abuse l5hlen here because PH_loc can hold only 64 bits of data */
#define TSO_MBUF_FLAGS(_mbuf)    ((_mbuf)->m_pkthdr.l5hlen)
#define TSO_MBUF_PACKETID(_mbuf) ((_mbuf)->m_pkthdr.PH_loc.sixteen[1])
#define TSO_MBUF_SEQNUM(_mbuf)   ((_mbuf)->m_pkthdr.PH_loc.thirtytwo[1])

static void sfxge_parse_tx_packet(struct mbuf *mbuf)
{
	struct ether_header *eh = mtod(mbuf, struct ether_header *);
	const struct tcphdr *th;
	struct tcphdr th_copy;

	/* Find network protocol and header */
	TSO_MBUF_PROTO(mbuf) = eh->ether_type;
	if (TSO_MBUF_PROTO(mbuf) == htons(ETHERTYPE_VLAN)) {
		struct ether_vlan_header *veh =
			mtod(mbuf, struct ether_vlan_header *);
		TSO_MBUF_PROTO(mbuf) = veh->evl_proto;
		mbuf->m_pkthdr.l2hlen = sizeof(*veh);
	} else {
		mbuf->m_pkthdr.l2hlen = sizeof(*eh);
	}

	/* Find TCP header */
	if (TSO_MBUF_PROTO(mbuf) == htons(ETHERTYPE_IP)) {
		const struct ip *iph = (const struct ip *)mtodo(mbuf, mbuf->m_pkthdr.l2hlen);

		KASSERT(iph->ip_p == IPPROTO_TCP,
			("TSO required on non-TCP packet"));
		mbuf->m_pkthdr.l3hlen = mbuf->m_pkthdr.l2hlen + 4 * iph->ip_hl;
		TSO_MBUF_PACKETID(mbuf) = iph->ip_id;
	} else {
		KASSERT(TSO_MBUF_PROTO(mbuf) == htons(ETHERTYPE_IPV6),
			("TSO required on non-IP packet"));
		KASSERT(((const struct ip6_hdr *)mtodo(mbuf, mbuf->m_pkthdr.l2hlen))->ip6_nxt ==
			IPPROTO_TCP,
			("TSO required on non-TCP packet"));
		mbuf->m_pkthdr.l3hlen = mbuf->m_pkthdr.l2hlen + sizeof(struct ip6_hdr);
		TSO_MBUF_PACKETID(mbuf) = 0;
	}

	KASSERT(mbuf->m_len >= mbuf->m_pkthdr.l3hlen,
		("network header is fragmented in mbuf"));

	/* We need TCP header including flags (window is the next) */
	if (mbuf->m_len < mbuf->m_pkthdr.l3hlen + offsetof(struct tcphdr, th_win)) {
		m_copydata(mbuf, mbuf->m_pkthdr.l3hlen, sizeof(th_copy),
			   (caddr_t)&th_copy);
		th = &th_copy;
	} else {
		th = (const struct tcphdr *)mtodo(mbuf, mbuf->m_pkthdr.l3hlen);
	}

	mbuf->m_pkthdr.l4hlen = mbuf->m_pkthdr.l3hlen + 4 * th->th_off;
	TSO_MBUF_SEQNUM(mbuf) = ntohl(th->th_seq);

	/* These flags must not be duplicated */
	/*
	 * RST should not be duplicated as well, but FreeBSD kernel
	 * generates TSO packets with RST flag. So, do not assert
	 * its absence.
	 */
	KASSERT(!(th->th_flags & (TH_URG | TH_SYN)),
		("incompatible TCP flag 0x%x on TSO packet",
		 th->th_flags & (TH_URG | TH_SYN)));
	TSO_MBUF_FLAGS(mbuf) = th->th_flags;
}
#endif

/*
 * TX start -- called by the stack.
 */
int
sfxge_if_transmit(struct ifnet *ifp, struct mbuf *m)
{
	struct sfxge_softc *sc;
	struct sfxge_txq *txq;
	int rc;

	sc = (struct sfxge_softc *)ifp->if_softc;

	/*
	 * Transmit may be called when interface is up from the kernel
	 * point of view, but not yet up (in progress) from the driver
	 * point of view. I.e. link aggregation bring up.
	 * Transmit may be called when interface is up from the driver
	 * point of view, but already down from the kernel point of
	 * view. I.e. Rx when interface shutdown is in progress.
	 */
	KASSERT((ifp->if_flags & IFF_UP) || (sc->if_flags & IFF_UP),
		("interface not up"));

	/* Pick the desired transmit queue. */
	if (m->m_pkthdr.csum_flags &
	    (CSUM_DELAY_DATA | CSUM_TCP_IPV6 | CSUM_UDP_IPV6 | CSUM_TSO)) {
		int index = 0;

		/* check if flowid is set */
		if (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) {
			uint32_t hash = m->m_pkthdr.flowid;

			index = sc->rx_indir_table[hash % SFXGE_RX_SCALE_MAX];
		}
#if SFXGE_TX_PARSE_EARLY
		if (m->m_pkthdr.csum_flags & CSUM_TSO)
			sfxge_parse_tx_packet(m);
#endif
		txq = sc->txq[SFXGE_TXQ_IP_TCP_UDP_CKSUM + index];
	} else if (m->m_pkthdr.csum_flags & CSUM_DELAY_IP) {
		txq = sc->txq[SFXGE_TXQ_IP_CKSUM];
	} else {
		txq = sc->txq[SFXGE_TXQ_NON_CKSUM];
	}

	rc = sfxge_tx_packet_add(txq, m);
	if (rc != 0)
		m_freem(m);

	return (rc);
}

/*
 * Software "TSO".  Not quite as good as doing it in hardware, but
 * still faster than segmenting in the stack.
 */

struct sfxge_tso_state {
	/* Output position */
	unsigned out_len;	/* Remaining length in current segment */
	unsigned seqnum;	/* Current sequence number */
	unsigned packet_space;	/* Remaining space in current packet */
	unsigned segs_space;	/* Remaining number of DMA segments
				   for the packet (FATSOv2 only) */

	/* Input position */
	uint64_t dma_addr;	/* DMA address of current position */
	unsigned in_len;	/* Remaining length in current mbuf */

	const struct mbuf *mbuf; /* Input mbuf (head of chain) */
	u_short protocol;	/* Network protocol (after VLAN decap) */
	ssize_t nh_off;		/* Offset of network header */
	ssize_t tcph_off;	/* Offset of TCP header */
	unsigned header_len;	/* Number of bytes of header */
	unsigned seg_size;	/* TCP segment size */
	int fw_assisted;	/* Use FW-assisted TSO */
	u_short packet_id;	/* IPv4 packet ID from the original packet */
	uint8_t tcp_flags;	/* TCP flags */
	efx_desc_t header_desc; /* Precomputed header descriptor for
				 * FW-assisted TSO */
};

#if !SFXGE_TX_PARSE_EARLY
static const struct ip *tso_iph(const struct sfxge_tso_state *tso)
{
	KASSERT(tso->protocol == htons(ETHERTYPE_IP),
		("tso_iph() in non-IPv4 state"));
	return (const struct ip *)(tso->mbuf->m_data + tso->nh_off);
}

static __unused const struct ip6_hdr *tso_ip6h(const struct sfxge_tso_state *tso)
{
	KASSERT(tso->protocol == htons(ETHERTYPE_IPV6),
		("tso_ip6h() in non-IPv6 state"));
	return (const struct ip6_hdr *)(tso->mbuf->m_data + tso->nh_off);
}

static const struct tcphdr *tso_tcph(const struct sfxge_tso_state *tso)
{
	return (const struct tcphdr *)(tso->mbuf->m_data + tso->tcph_off);
}
#endif


/* Size of preallocated TSO header buffers.  Larger blocks must be
 * allocated from the heap.
 */
#define	TSOH_STD_SIZE	128

/* At most half the descriptors in the queue at any time will refer to
 * a TSO header buffer, since they must always be followed by a
 * payload descriptor referring to an mbuf.
 */
#define	TSOH_COUNT(_txq_entries)	((_txq_entries) / 2u)
#define	TSOH_PER_PAGE	(PAGE_SIZE / TSOH_STD_SIZE)
#define	TSOH_PAGE_COUNT(_txq_entries)	\
	howmany(TSOH_COUNT(_txq_entries), TSOH_PER_PAGE)

static int tso_init(struct sfxge_txq *txq)
{
	struct sfxge_softc *sc = txq->sc;
	unsigned int tsoh_page_count = TSOH_PAGE_COUNT(sc->txq_entries);
	int i, rc;

	/* Allocate TSO header buffers */
	txq->tsoh_buffer = malloc(tsoh_page_count * sizeof(txq->tsoh_buffer[0]),
				  M_SFXGE, M_WAITOK);

	for (i = 0; i < tsoh_page_count; i++) {
		rc = sfxge_dma_alloc(sc, PAGE_SIZE, &txq->tsoh_buffer[i]);
		if (rc != 0)
			goto fail;
	}

	return (0);

fail:
	while (i-- > 0)
		sfxge_dma_free(&txq->tsoh_buffer[i]);
	free(txq->tsoh_buffer, M_SFXGE);
	txq->tsoh_buffer = NULL;
	return (rc);
}

static void tso_fini(struct sfxge_txq *txq)
{
	int i;

	if (txq->tsoh_buffer != NULL) {
		for (i = 0; i < TSOH_PAGE_COUNT(txq->sc->txq_entries); i++)
			sfxge_dma_free(&txq->tsoh_buffer[i]);
		free(txq->tsoh_buffer, M_SFXGE);
	}
}

static void tso_start(struct sfxge_txq *txq, struct sfxge_tso_state *tso,
		      const bus_dma_segment_t *hdr_dma_seg,
		      struct mbuf *mbuf)
{
	const efx_nic_cfg_t *encp = efx_nic_cfg_get(txq->sc->enp);
#if !SFXGE_TX_PARSE_EARLY
	struct ether_header *eh = mtod(mbuf, struct ether_header *);
	const struct tcphdr *th;
	struct tcphdr th_copy;
#endif

	tso->fw_assisted = txq->tso_fw_assisted;
	tso->mbuf = mbuf;

	/* Find network protocol and header */
#if !SFXGE_TX_PARSE_EARLY
	tso->protocol = eh->ether_type;
	if (tso->protocol == htons(ETHERTYPE_VLAN)) {
		struct ether_vlan_header *veh =
			mtod(mbuf, struct ether_vlan_header *);
		tso->protocol = veh->evl_proto;
		tso->nh_off = sizeof(*veh);
	} else {
		tso->nh_off = sizeof(*eh);
	}
#else
	tso->protocol = TSO_MBUF_PROTO(mbuf);
	tso->nh_off = mbuf->m_pkthdr.l2hlen;
	tso->tcph_off = mbuf->m_pkthdr.l3hlen;
	tso->packet_id = TSO_MBUF_PACKETID(mbuf);
#endif

#if !SFXGE_TX_PARSE_EARLY
	/* Find TCP header */
	if (tso->protocol == htons(ETHERTYPE_IP)) {
		KASSERT(tso_iph(tso)->ip_p == IPPROTO_TCP,
			("TSO required on non-TCP packet"));
		tso->tcph_off = tso->nh_off + 4 * tso_iph(tso)->ip_hl;
		tso->packet_id = tso_iph(tso)->ip_id;
	} else {
		KASSERT(tso->protocol == htons(ETHERTYPE_IPV6),
			("TSO required on non-IP packet"));
		KASSERT(tso_ip6h(tso)->ip6_nxt == IPPROTO_TCP,
			("TSO required on non-TCP packet"));
		tso->tcph_off = tso->nh_off + sizeof(struct ip6_hdr);
		tso->packet_id = 0;
	}
#endif


	if (tso->fw_assisted &&
	    __predict_false(tso->tcph_off >
			    encp->enc_tx_tso_tcp_header_offset_limit)) {
		tso->fw_assisted = 0;
	}


#if !SFXGE_TX_PARSE_EARLY
	KASSERT(mbuf->m_len >= tso->tcph_off,
		("network header is fragmented in mbuf"));
	/* We need TCP header including flags (window is the next) */
	if (mbuf->m_len < tso->tcph_off + offsetof(struct tcphdr, th_win)) {
		m_copydata(tso->mbuf, tso->tcph_off, sizeof(th_copy),
			   (caddr_t)&th_copy);
		th = &th_copy;
	} else {
		th = tso_tcph(tso);
	}
	tso->header_len = tso->tcph_off + 4 * th->th_off;
#else
	tso->header_len = mbuf->m_pkthdr.l4hlen;
#endif
	tso->seg_size = mbuf->m_pkthdr.tso_segsz;

#if !SFXGE_TX_PARSE_EARLY
	tso->seqnum = ntohl(th->th_seq);

	/* These flags must not be duplicated */
	/*
	 * RST should not be duplicated as well, but FreeBSD kernel
	 * generates TSO packets with RST flag. So, do not assert
	 * its absence.
	 */
	KASSERT(!(th->th_flags & (TH_URG | TH_SYN)),
		("incompatible TCP flag 0x%x on TSO packet",
		 th->th_flags & (TH_URG | TH_SYN)));
	tso->tcp_flags = th->th_flags;
#else
	tso->seqnum = TSO_MBUF_SEQNUM(mbuf);
	tso->tcp_flags = TSO_MBUF_FLAGS(mbuf);
#endif

	tso->out_len = mbuf->m_pkthdr.len - tso->header_len;

	if (tso->fw_assisted) {
		if (hdr_dma_seg->ds_len >= tso->header_len)
			efx_tx_qdesc_dma_create(txq->common,
						hdr_dma_seg->ds_addr,
						tso->header_len,
						B_FALSE,
						&tso->header_desc);
		else
			tso->fw_assisted = 0;
	}
}

/*
 * tso_fill_packet_with_fragment - form descriptors for the current fragment
 *
 * Form descriptors for the current fragment, until we reach the end
 * of fragment or end-of-packet.  Return 0 on success, 1 if not enough
 * space.
 */
static void tso_fill_packet_with_fragment(struct sfxge_txq *txq,
					  struct sfxge_tso_state *tso)
{
	efx_desc_t *desc;
	int n;
	uint64_t dma_addr = tso->dma_addr;
	boolean_t eop;

	if (tso->in_len == 0 || tso->packet_space == 0)
		return;

	KASSERT(tso->in_len > 0, ("TSO input length went negative"));
	KASSERT(tso->packet_space > 0, ("TSO packet space went negative"));

	if (tso->fw_assisted & SFXGE_FATSOV2) {
		n = tso->in_len;
		tso->out_len -= n;
		tso->seqnum += n;
		tso->in_len = 0;
		if (n < tso->packet_space) {
			tso->packet_space -= n;
			tso->segs_space--;
		} else {
			tso->packet_space = tso->seg_size -
			    (n - tso->packet_space) % tso->seg_size;
			tso->segs_space =
			    EFX_TX_FATSOV2_DMA_SEGS_PER_PKT_MAX - 1 -
			    (tso->packet_space != tso->seg_size);
		}
	} else {
		n = min(tso->in_len, tso->packet_space);
		tso->packet_space -= n;
		tso->out_len -= n;
		tso->dma_addr += n;
		tso->in_len -= n;
	}

	/*
	 * It is OK to use binary OR below to avoid extra branching
	 * since all conditions may always be checked.
	 */
	eop = (tso->out_len == 0) | (tso->packet_space == 0) |
	    (tso->segs_space == 0);

	desc = &txq->pend_desc[txq->n_pend_desc++];
	efx_tx_qdesc_dma_create(txq->common, dma_addr, n, eop, desc);
}

/* Callback from bus_dmamap_load() for long TSO headers. */
static void tso_map_long_header(void *dma_addr_ret,
				bus_dma_segment_t *segs, int nseg,
				int error)
{
	*(uint64_t *)dma_addr_ret = ((__predict_true(error == 0) &&
				      __predict_true(nseg == 1)) ?
				     segs->ds_addr : 0);
}

/*
 * tso_start_new_packet - generate a new header and prepare for the new packet
 *
 * Generate a new header and prepare for the new packet.  Return 0 on
 * success, or an error code if failed to alloc header.
 */
static int tso_start_new_packet(struct sfxge_txq *txq,
				struct sfxge_tso_state *tso,
				unsigned int *idp)
{
	unsigned int id = *idp;
	struct tcphdr *tsoh_th;
	unsigned ip_length;
	caddr_t header;
	uint64_t dma_addr;
	bus_dmamap_t map;
	efx_desc_t *desc;
	int rc;

	if (tso->fw_assisted) {
		if (tso->fw_assisted & SFXGE_FATSOV2) {
			/* Add 2 FATSOv2 option descriptors */
			desc = &txq->pend_desc[txq->n_pend_desc];
			efx_tx_qdesc_tso2_create(txq->common,
						 tso->packet_id,
						 tso->seqnum,
						 tso->seg_size,
						 desc,
						 EFX_TX_FATSOV2_OPT_NDESCS);
			desc += EFX_TX_FATSOV2_OPT_NDESCS;
			txq->n_pend_desc += EFX_TX_FATSOV2_OPT_NDESCS;
			KASSERT(txq->stmp[id].flags == 0, ("stmp flags are not 0"));
			id = (id + EFX_TX_FATSOV2_OPT_NDESCS) & txq->ptr_mask;

			tso->segs_space =
			    EFX_TX_FATSOV2_DMA_SEGS_PER_PKT_MAX - 1;
		} else {
			uint8_t tcp_flags = tso->tcp_flags;

			if (tso->out_len > tso->seg_size)
				tcp_flags &= ~(TH_FIN | TH_PUSH);

			/* Add FATSOv1 option descriptor */
			desc = &txq->pend_desc[txq->n_pend_desc++];
			efx_tx_qdesc_tso_create(txq->common,
						tso->packet_id,
						tso->seqnum,
						tcp_flags,
						desc++);
			KASSERT(txq->stmp[id].flags == 0, ("stmp flags are not 0"));
			id = (id + 1) & txq->ptr_mask;

			tso->seqnum += tso->seg_size;
			tso->segs_space = UINT_MAX;
		}

		/* Header DMA descriptor */
		*desc = tso->header_desc;
		txq->n_pend_desc++;
		KASSERT(txq->stmp[id].flags == 0, ("stmp flags are not 0"));
		id = (id + 1) & txq->ptr_mask;
	} else {
		/* Allocate a DMA-mapped header buffer. */
		if (__predict_true(tso->header_len <= TSOH_STD_SIZE)) {
			unsigned int page_index = (id / 2) / TSOH_PER_PAGE;
			unsigned int buf_index = (id / 2) % TSOH_PER_PAGE;

			header = (txq->tsoh_buffer[page_index].esm_base +
				  buf_index * TSOH_STD_SIZE);
			dma_addr = (txq->tsoh_buffer[page_index].esm_addr +
				    buf_index * TSOH_STD_SIZE);
			map = txq->tsoh_buffer[page_index].esm_map;

			KASSERT(txq->stmp[id].flags == 0,
				("stmp flags are not 0"));
		} else {
			struct sfxge_tx_mapping *stmp = &txq->stmp[id];

			/* We cannot use bus_dmamem_alloc() as that may sleep */
			header = malloc(tso->header_len, M_SFXGE, M_NOWAIT);
			if (__predict_false(!header))
				return (ENOMEM);
			rc = bus_dmamap_load(txq->packet_dma_tag, stmp->map,
					     header, tso->header_len,
					     tso_map_long_header, &dma_addr,
					     BUS_DMA_NOWAIT);
			if (__predict_false(dma_addr == 0)) {
				if (rc == 0) {
					/* Succeeded but got >1 segment */
					bus_dmamap_unload(txq->packet_dma_tag,
							  stmp->map);
					rc = EINVAL;
				}
				free(header, M_SFXGE);
				return (rc);
			}
			map = stmp->map;

			txq->tso_long_headers++;
			stmp->u.heap_buf = header;
			stmp->flags = TX_BUF_UNMAP;
		}

		tsoh_th = (struct tcphdr *)(header + tso->tcph_off);

		/* Copy and update the headers. */
		m_copydata(tso->mbuf, 0, tso->header_len, header);

		tsoh_th->th_seq = htonl(tso->seqnum);
		tso->seqnum += tso->seg_size;
		if (tso->out_len > tso->seg_size) {
			/* This packet will not finish the TSO burst. */
			ip_length = tso->header_len - tso->nh_off + tso->seg_size;
			tsoh_th->th_flags &= ~(TH_FIN | TH_PUSH);
		} else {
			/* This packet will be the last in the TSO burst. */
			ip_length = tso->header_len - tso->nh_off + tso->out_len;
		}

		if (tso->protocol == htons(ETHERTYPE_IP)) {
			struct ip *tsoh_iph = (struct ip *)(header + tso->nh_off);
			tsoh_iph->ip_len = htons(ip_length);
			/* XXX We should increment ip_id, but FreeBSD doesn't
			 * currently allocate extra IDs for multiple segments.
			 */
		} else {
			struct ip6_hdr *tsoh_iph =
				(struct ip6_hdr *)(header + tso->nh_off);
			tsoh_iph->ip6_plen = htons(ip_length - sizeof(*tsoh_iph));
		}

		/* Make the header visible to the hardware. */
		bus_dmamap_sync(txq->packet_dma_tag, map, BUS_DMASYNC_PREWRITE);

		/* Form a descriptor for this header. */
		desc = &txq->pend_desc[txq->n_pend_desc++];
		efx_tx_qdesc_dma_create(txq->common,
					dma_addr,
					tso->header_len,
					0,
					desc);
		id = (id + 1) & txq->ptr_mask;

		tso->segs_space = UINT_MAX;
	}
	tso->packet_space = tso->seg_size;
	txq->tso_packets++;
	*idp = id;

	return (0);
}

static int
sfxge_tx_queue_tso(struct sfxge_txq *txq, struct mbuf *mbuf,
		   const bus_dma_segment_t *dma_seg, int n_dma_seg,
		   int vlan_tagged)
{
	struct sfxge_tso_state tso;
	unsigned int id;
	unsigned skipped = 0;

	tso_start(txq, &tso, dma_seg, mbuf);

	while (dma_seg->ds_len + skipped <= tso.header_len) {
		skipped += dma_seg->ds_len;
		--n_dma_seg;
		KASSERT(n_dma_seg, ("no payload found in TSO packet"));
		++dma_seg;
	}
	tso.in_len = dma_seg->ds_len - (tso.header_len - skipped);
	tso.dma_addr = dma_seg->ds_addr + (tso.header_len - skipped);

	id = (txq->added + vlan_tagged) & txq->ptr_mask;
	if (__predict_false(tso_start_new_packet(txq, &tso, &id)))
		return (-1);

	while (1) {
		tso_fill_packet_with_fragment(txq, &tso);
		/* Exactly one DMA descriptor is added */
		KASSERT(txq->stmp[id].flags == 0, ("stmp flags are not 0"));
		id = (id + 1) & txq->ptr_mask;

		/* Move onto the next fragment? */
		if (tso.in_len == 0) {
			--n_dma_seg;
			if (n_dma_seg == 0)
				break;
			++dma_seg;
			tso.in_len = dma_seg->ds_len;
			tso.dma_addr = dma_seg->ds_addr;
		}

		/* End of packet? */
		if ((tso.packet_space == 0) | (tso.segs_space == 0)) {
			unsigned int n_fatso_opt_desc =
			    (tso.fw_assisted & SFXGE_FATSOV2) ?
			    EFX_TX_FATSOV2_OPT_NDESCS :
			    (tso.fw_assisted & SFXGE_FATSOV1) ? 1 : 0;

			/* If the queue is now full due to tiny MSS,
			 * or we can't create another header, discard
			 * the remainder of the input mbuf but do not
			 * roll back the work we have done.
			 */
			if (txq->n_pend_desc + n_fatso_opt_desc +
			    1 /* header */ + n_dma_seg > txq->max_pkt_desc) {
				txq->tso_pdrop_too_many++;
				break;
			}
			if (__predict_false(tso_start_new_packet(txq, &tso,
								 &id))) {
				txq->tso_pdrop_no_rsrc++;
				break;
			}
		}
	}

	txq->tso_bursts++;
	return (id);
}

static void
sfxge_tx_qunblock(struct sfxge_txq *txq)
{
	struct sfxge_softc *sc;
	struct sfxge_evq *evq;

	sc = txq->sc;
	evq = sc->evq[txq->evq_index];

	SFXGE_EVQ_LOCK_ASSERT_OWNED(evq);

	if (__predict_false(txq->init_state != SFXGE_TXQ_STARTED))
		return;

	SFXGE_TXQ_LOCK(txq);

	if (txq->blocked) {
		unsigned int level;

		level = txq->added - txq->completed;
		if (level <= SFXGE_TXQ_UNBLOCK_LEVEL(txq->entries)) {
			/* reaped must be in sync with blocked */
			sfxge_tx_qreap(txq);
			txq->blocked = 0;
		}
	}

	sfxge_tx_qdpl_service(txq);
	/* note: lock has been dropped */
}

void
sfxge_tx_qflush_done(struct sfxge_txq *txq)
{

	txq->flush_state = SFXGE_FLUSH_DONE;
}

static void
sfxge_tx_qstop(struct sfxge_softc *sc, unsigned int index)
{
	struct sfxge_txq *txq;
	struct sfxge_evq *evq;
	unsigned int count;

	SFXGE_ADAPTER_LOCK_ASSERT_OWNED(sc);

	txq = sc->txq[index];
	evq = sc->evq[txq->evq_index];

	SFXGE_EVQ_LOCK(evq);
	SFXGE_TXQ_LOCK(txq);

	KASSERT(txq->init_state == SFXGE_TXQ_STARTED,
	    ("txq->init_state != SFXGE_TXQ_STARTED"));

	txq->init_state = SFXGE_TXQ_INITIALIZED;

	if (txq->flush_state != SFXGE_FLUSH_DONE) {
		txq->flush_state = SFXGE_FLUSH_PENDING;

		SFXGE_EVQ_UNLOCK(evq);
		SFXGE_TXQ_UNLOCK(txq);

		/* Flush the transmit queue. */
		if (efx_tx_qflush(txq->common) != 0) {
			log(LOG_ERR, "%s: Flushing Tx queue %u failed\n",
			    device_get_nameunit(sc->dev), index);
			txq->flush_state = SFXGE_FLUSH_DONE;
		} else {
			count = 0;
			do {
				/* Spin for 100ms. */
				DELAY(100000);
				if (txq->flush_state != SFXGE_FLUSH_PENDING)
					break;
			} while (++count < 20);
		}
		SFXGE_EVQ_LOCK(evq);
		SFXGE_TXQ_LOCK(txq);

		KASSERT(txq->flush_state != SFXGE_FLUSH_FAILED,
		    ("txq->flush_state == SFXGE_FLUSH_FAILED"));

		if (txq->flush_state != SFXGE_FLUSH_DONE) {
			/* Flush timeout */
			log(LOG_ERR, "%s: Cannot flush Tx queue %u\n",
			    device_get_nameunit(sc->dev), index);
			txq->flush_state = SFXGE_FLUSH_DONE;
		}
	}

	txq->blocked = 0;
	txq->pending = txq->added;

	sfxge_tx_qcomplete(txq, evq);
	KASSERT(txq->completed == txq->added,
	    ("txq->completed != txq->added"));

	sfxge_tx_qreap(txq);
	KASSERT(txq->reaped == txq->completed,
	    ("txq->reaped != txq->completed"));

	txq->added = 0;
	txq->pending = 0;
	txq->completed = 0;
	txq->reaped = 0;

	/* Destroy the common code transmit queue. */
	efx_tx_qdestroy(txq->common);
	txq->common = NULL;

	efx_sram_buf_tbl_clear(sc->enp, txq->buf_base_id,
	    EFX_TXQ_NBUFS(sc->txq_entries));

	SFXGE_EVQ_UNLOCK(evq);
	SFXGE_TXQ_UNLOCK(txq);
}

/*
 * Estimate maximum number of Tx descriptors required for TSO packet.
 * With minimum MSS and maximum mbuf length we might need more (even
 * than a ring-ful of descriptors), but this should not happen in
 * practice except due to deliberate attack.  In that case we will
 * truncate the output at a packet boundary.
 */
static unsigned int
sfxge_tx_max_pkt_desc(const struct sfxge_softc *sc, enum sfxge_txq_type type,
		      unsigned int tso_fw_assisted)
{
	/* One descriptor for every input fragment */
	unsigned int max_descs = SFXGE_TX_MAPPING_MAX_SEG;
	unsigned int sw_tso_max_descs;
	unsigned int fa_tso_v1_max_descs = 0;
	unsigned int fa_tso_v2_max_descs = 0;

	/* VLAN tagging Tx option descriptor may be required */
	if (efx_nic_cfg_get(sc->enp)->enc_hw_tx_insert_vlan_enabled)
		max_descs++;

	if (type == SFXGE_TXQ_IP_TCP_UDP_CKSUM) {
		/*
		 * Plus header and payload descriptor for each output segment.
		 * Minus one since header fragment is already counted.
		 * Even if FATSO is used, we should be ready to fallback
		 * to do it in the driver.
		 */
		sw_tso_max_descs = SFXGE_TSO_MAX_SEGS * 2 - 1;

		/* FW assisted TSOv1 requires one more descriptor per segment
		 * in comparison to SW TSO */
		if (tso_fw_assisted & SFXGE_FATSOV1)
			fa_tso_v1_max_descs =
			    sw_tso_max_descs + SFXGE_TSO_MAX_SEGS;

		/* FW assisted TSOv2 requires 3 (2 FATSO plus header) extra
		 * descriptors per superframe limited by number of DMA fetches
		 * per packet. The first packet header is already counted.
		 */
		if (tso_fw_assisted & SFXGE_FATSOV2) {
			fa_tso_v2_max_descs =
			    howmany(SFXGE_TX_MAPPING_MAX_SEG,
				    EFX_TX_FATSOV2_DMA_SEGS_PER_PKT_MAX - 1) *
			    (EFX_TX_FATSOV2_OPT_NDESCS + 1) - 1;
		}

		max_descs += MAX(sw_tso_max_descs,
				 MAX(fa_tso_v1_max_descs, fa_tso_v2_max_descs));
	}

	return (max_descs);
}

static int
sfxge_tx_qstart(struct sfxge_softc *sc, unsigned int index)
{
	struct sfxge_txq *txq;
	efsys_mem_t *esmp;
	uint16_t flags;
	unsigned int tso_fw_assisted;
	struct sfxge_evq *evq;
	unsigned int desc_index;
	int rc;

	SFXGE_ADAPTER_LOCK_ASSERT_OWNED(sc);

	txq = sc->txq[index];
	esmp = &txq->mem;
	evq = sc->evq[txq->evq_index];

	KASSERT(txq->init_state == SFXGE_TXQ_INITIALIZED,
	    ("txq->init_state != SFXGE_TXQ_INITIALIZED"));
	KASSERT(evq->init_state == SFXGE_EVQ_STARTED,
	    ("evq->init_state != SFXGE_EVQ_STARTED"));

	/* Program the buffer table. */
	if ((rc = efx_sram_buf_tbl_set(sc->enp, txq->buf_base_id, esmp,
	    EFX_TXQ_NBUFS(sc->txq_entries))) != 0)
		return (rc);

	/* Determine the kind of queue we are creating. */
	tso_fw_assisted = 0;
	switch (txq->type) {
	case SFXGE_TXQ_NON_CKSUM:
		flags = 0;
		break;
	case SFXGE_TXQ_IP_CKSUM:
		flags = EFX_TXQ_CKSUM_IPV4;
		break;
	case SFXGE_TXQ_IP_TCP_UDP_CKSUM:
		flags = EFX_TXQ_CKSUM_IPV4 | EFX_TXQ_CKSUM_TCPUDP;
		tso_fw_assisted = sc->tso_fw_assisted;
		if (tso_fw_assisted & SFXGE_FATSOV2)
			flags |= EFX_TXQ_FATSOV2;
		break;
	default:
		KASSERT(0, ("Impossible TX queue"));
		flags = 0;
		break;
	}

	/* Create the common code transmit queue. */
	if ((rc = efx_tx_qcreate(sc->enp, index, txq->type, esmp,
	    sc->txq_entries, txq->buf_base_id, flags, evq->common,
	    &txq->common, &desc_index)) != 0) {
		/* Retry if no FATSOv2 resources, otherwise fail */
		if ((rc != ENOSPC) || (~flags & EFX_TXQ_FATSOV2))
			goto fail;

		/* Looks like all FATSOv2 contexts are used */
		flags &= ~EFX_TXQ_FATSOV2;
		tso_fw_assisted &= ~SFXGE_FATSOV2;
		if ((rc = efx_tx_qcreate(sc->enp, index, txq->type, esmp,
		    sc->txq_entries, txq->buf_base_id, flags, evq->common,
		    &txq->common, &desc_index)) != 0)
			goto fail;
	}

	/* Initialise queue descriptor indexes */
	txq->added = txq->pending = txq->completed = txq->reaped = desc_index;

	SFXGE_TXQ_LOCK(txq);

	/* Enable the transmit queue. */
	efx_tx_qenable(txq->common);

	txq->init_state = SFXGE_TXQ_STARTED;
	txq->flush_state = SFXGE_FLUSH_REQUIRED;
	txq->tso_fw_assisted = tso_fw_assisted;

	txq->max_pkt_desc = sfxge_tx_max_pkt_desc(sc, txq->type,
						  tso_fw_assisted);

	SFXGE_TXQ_UNLOCK(txq);

	return (0);

fail:
	efx_sram_buf_tbl_clear(sc->enp, txq->buf_base_id,
	    EFX_TXQ_NBUFS(sc->txq_entries));
	return (rc);
}

void
sfxge_tx_stop(struct sfxge_softc *sc)
{
	int index;

	index = sc->txq_count;
	while (--index >= 0)
		sfxge_tx_qstop(sc, index);

	/* Tear down the transmit module */
	efx_tx_fini(sc->enp);
}

int
sfxge_tx_start(struct sfxge_softc *sc)
{
	int index;
	int rc;

	/* Initialize the common code transmit module. */
	if ((rc = efx_tx_init(sc->enp)) != 0)
		return (rc);

	for (index = 0; index < sc->txq_count; index++) {
		if ((rc = sfxge_tx_qstart(sc, index)) != 0)
			goto fail;
	}

	return (0);

fail:
	while (--index >= 0)
		sfxge_tx_qstop(sc, index);

	efx_tx_fini(sc->enp);

	return (rc);
}

static int
sfxge_txq_stat_init(struct sfxge_txq *txq, struct sysctl_oid *txq_node)
{
	struct sysctl_ctx_list *ctx = device_get_sysctl_ctx(txq->sc->dev);
	struct sysctl_oid *stat_node;
	unsigned int id;

	stat_node = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(txq_node), OID_AUTO,
				    "stats", CTLFLAG_RD, NULL,
				    "Tx queue statistics");
	if (stat_node == NULL)
		return (ENOMEM);

	for (id = 0; id < nitems(sfxge_tx_stats); id++) {
		SYSCTL_ADD_ULONG(
		    ctx, SYSCTL_CHILDREN(stat_node), OID_AUTO,
		    sfxge_tx_stats[id].name, CTLFLAG_RD | CTLFLAG_STATS,
		    (unsigned long *)((caddr_t)txq + sfxge_tx_stats[id].offset),
		    "");
	}

	return (0);
}

/**
 * Destroy a transmit queue.
 */
static void
sfxge_tx_qfini(struct sfxge_softc *sc, unsigned int index)
{
	struct sfxge_txq *txq;
	unsigned int nmaps;

	txq = sc->txq[index];

	KASSERT(txq->init_state == SFXGE_TXQ_INITIALIZED,
	    ("txq->init_state != SFXGE_TXQ_INITIALIZED"));

	if (txq->type == SFXGE_TXQ_IP_TCP_UDP_CKSUM)
		tso_fini(txq);

	/* Free the context arrays. */
	free(txq->pend_desc, M_SFXGE);
	nmaps = sc->txq_entries;
	while (nmaps-- != 0)
		bus_dmamap_destroy(txq->packet_dma_tag, txq->stmp[nmaps].map);
	free(txq->stmp, M_SFXGE);

	/* Release DMA memory mapping. */
	sfxge_dma_free(&txq->mem);

	sc->txq[index] = NULL;

	SFXGE_TXQ_LOCK_DESTROY(txq);

	free(txq, M_SFXGE);
}

static int
sfxge_tx_qinit(struct sfxge_softc *sc, unsigned int txq_index,
	       enum sfxge_txq_type type, unsigned int evq_index)
{
	char name[16];
	struct sysctl_ctx_list *ctx = device_get_sysctl_ctx(sc->dev);
	struct sysctl_oid *txq_node;
	struct sfxge_txq *txq;
	struct sfxge_evq *evq;
	struct sfxge_tx_dpl *stdp;
	struct sysctl_oid *dpl_node;
	efsys_mem_t *esmp;
	unsigned int nmaps;
	int rc;

	txq = malloc(sizeof(struct sfxge_txq), M_SFXGE, M_ZERO | M_WAITOK);
	txq->sc = sc;
	txq->entries = sc->txq_entries;
	txq->ptr_mask = txq->entries - 1;

	sc->txq[txq_index] = txq;
	esmp = &txq->mem;

	evq = sc->evq[evq_index];

	/* Allocate and zero DMA space for the descriptor ring. */
	if ((rc = sfxge_dma_alloc(sc, EFX_TXQ_SIZE(sc->txq_entries), esmp)) != 0)
		return (rc);

	/* Allocate buffer table entries. */
	sfxge_sram_buf_tbl_alloc(sc, EFX_TXQ_NBUFS(sc->txq_entries),
				 &txq->buf_base_id);

	/* Create a DMA tag for packet mappings. */
	if (bus_dma_tag_create(sc->parent_dma_tag, 1, 0x1000,
	    MIN(0x3FFFFFFFFFFFUL, BUS_SPACE_MAXADDR), BUS_SPACE_MAXADDR, NULL,
	    NULL, 0x11000, SFXGE_TX_MAPPING_MAX_SEG, 0x1000, 0, NULL, NULL,
	    &txq->packet_dma_tag) != 0) {
		device_printf(sc->dev, "Couldn't allocate txq DMA tag\n");
		rc = ENOMEM;
		goto fail;
	}

	/* Allocate pending descriptor array for batching writes. */
	txq->pend_desc = malloc(sizeof(efx_desc_t) * sc->txq_entries,
				M_SFXGE, M_ZERO | M_WAITOK);

	/* Allocate and initialise mbuf DMA mapping array. */
	txq->stmp = malloc(sizeof(struct sfxge_tx_mapping) * sc->txq_entries,
	    M_SFXGE, M_ZERO | M_WAITOK);
	for (nmaps = 0; nmaps < sc->txq_entries; nmaps++) {
		rc = bus_dmamap_create(txq->packet_dma_tag, 0,
				       &txq->stmp[nmaps].map);
		if (rc != 0)
			goto fail2;
	}

	snprintf(name, sizeof(name), "%u", txq_index);
	txq_node = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(sc->txqs_node),
				   OID_AUTO, name, CTLFLAG_RD, NULL, "");
	if (txq_node == NULL) {
		rc = ENOMEM;
		goto fail_txq_node;
	}

	if (type == SFXGE_TXQ_IP_TCP_UDP_CKSUM &&
	    (rc = tso_init(txq)) != 0)
		goto fail3;

	if (sfxge_tx_dpl_get_max <= 0) {
		log(LOG_ERR, "%s=%d must be greater than 0",
		    SFXGE_PARAM_TX_DPL_GET_MAX, sfxge_tx_dpl_get_max);
		rc = EINVAL;
		goto fail_tx_dpl_get_max;
	}
	if (sfxge_tx_dpl_get_non_tcp_max <= 0) {
		log(LOG_ERR, "%s=%d must be greater than 0",
		    SFXGE_PARAM_TX_DPL_GET_NON_TCP_MAX,
		    sfxge_tx_dpl_get_non_tcp_max);
		rc = EINVAL;
		goto fail_tx_dpl_get_max;
	}
	if (sfxge_tx_dpl_put_max < 0) {
		log(LOG_ERR, "%s=%d must be greater or equal to 0",
		    SFXGE_PARAM_TX_DPL_PUT_MAX, sfxge_tx_dpl_put_max);
		rc = EINVAL;
		goto fail_tx_dpl_put_max;
	}

	/* Initialize the deferred packet list. */
	stdp = &txq->dpl;
	stdp->std_put_max = sfxge_tx_dpl_put_max;
	stdp->std_get_max = sfxge_tx_dpl_get_max;
	stdp->std_get_non_tcp_max = sfxge_tx_dpl_get_non_tcp_max;
	stdp->std_getp = &stdp->std_get;

	SFXGE_TXQ_LOCK_INIT(txq, device_get_nameunit(sc->dev), txq_index);

	dpl_node = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(txq_node), OID_AUTO,
				   "dpl", CTLFLAG_RD, NULL,
				   "Deferred packet list statistics");
	if (dpl_node == NULL) {
		rc = ENOMEM;
		goto fail_dpl_node;
	}

	SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(dpl_node), OID_AUTO,
			"get_count", CTLFLAG_RD | CTLFLAG_STATS,
			&stdp->std_get_count, 0, "");
	SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(dpl_node), OID_AUTO,
			"get_non_tcp_count", CTLFLAG_RD | CTLFLAG_STATS,
			&stdp->std_get_non_tcp_count, 0, "");
	SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(dpl_node), OID_AUTO,
			"get_hiwat", CTLFLAG_RD | CTLFLAG_STATS,
			&stdp->std_get_hiwat, 0, "");
	SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(dpl_node), OID_AUTO,
			"put_hiwat", CTLFLAG_RD | CTLFLAG_STATS,
			&stdp->std_put_hiwat, 0, "");

	rc = sfxge_txq_stat_init(txq, txq_node);
	if (rc != 0)
		goto fail_txq_stat_init;

	txq->type = type;
	txq->evq_index = evq_index;
	txq->txq_index = txq_index;
	txq->init_state = SFXGE_TXQ_INITIALIZED;
	txq->hw_vlan_tci = 0;

	return (0);

fail_txq_stat_init:
fail_dpl_node:
fail_tx_dpl_put_max:
fail_tx_dpl_get_max:
fail3:
fail_txq_node:
	free(txq->pend_desc, M_SFXGE);
fail2:
	while (nmaps-- != 0)
		bus_dmamap_destroy(txq->packet_dma_tag, txq->stmp[nmaps].map);
	free(txq->stmp, M_SFXGE);
	bus_dma_tag_destroy(txq->packet_dma_tag);

fail:
	sfxge_dma_free(esmp);

	return (rc);
}

static int
sfxge_tx_stat_handler(SYSCTL_HANDLER_ARGS)
{
	struct sfxge_softc *sc = arg1;
	unsigned int id = arg2;
	unsigned long sum;
	unsigned int index;

	/* Sum across all TX queues */
	sum = 0;
	for (index = 0; index < sc->txq_count; index++)
		sum += *(unsigned long *)((caddr_t)sc->txq[index] +
					  sfxge_tx_stats[id].offset);

	return (SYSCTL_OUT(req, &sum, sizeof(sum)));
}

static void
sfxge_tx_stat_init(struct sfxge_softc *sc)
{
	struct sysctl_ctx_list *ctx = device_get_sysctl_ctx(sc->dev);
	struct sysctl_oid_list *stat_list;
	unsigned int id;

	stat_list = SYSCTL_CHILDREN(sc->stats_node);

	for (id = 0; id < nitems(sfxge_tx_stats); id++) {
		SYSCTL_ADD_PROC(
			ctx, stat_list,
			OID_AUTO, sfxge_tx_stats[id].name,
			CTLTYPE_ULONG|CTLFLAG_RD,
			sc, id, sfxge_tx_stat_handler, "LU",
			"");
	}
}

uint64_t
sfxge_tx_get_drops(struct sfxge_softc *sc)
{
	unsigned int index;
	uint64_t drops = 0;
	struct sfxge_txq *txq;

	/* Sum across all TX queues */
	for (index = 0; index < sc->txq_count; index++) {
		txq = sc->txq[index];
		/*
		 * In theory, txq->put_overflow and txq->netdown_drops
		 * should use atomic operation and other should be
		 * obtained under txq lock, but it is just statistics.
		 */
		drops += txq->drops + txq->get_overflow +
			 txq->get_non_tcp_overflow +
			 txq->put_overflow + txq->netdown_drops +
			 txq->tso_pdrop_too_many + txq->tso_pdrop_no_rsrc;
	}
	return (drops);
}

void
sfxge_tx_fini(struct sfxge_softc *sc)
{
	int index;

	index = sc->txq_count;
	while (--index >= 0)
		sfxge_tx_qfini(sc, index);

	sc->txq_count = 0;
}


int
sfxge_tx_init(struct sfxge_softc *sc)
{
	const efx_nic_cfg_t *encp = efx_nic_cfg_get(sc->enp);
	struct sfxge_intr *intr;
	int index;
	int rc;

	intr = &sc->intr;

	KASSERT(intr->state == SFXGE_INTR_INITIALIZED,
	    ("intr->state != SFXGE_INTR_INITIALIZED"));

	sc->txq_count = SFXGE_TXQ_NTYPES - 1 + sc->intr.n_alloc;

	sc->tso_fw_assisted = sfxge_tso_fw_assisted;
	if ((~encp->enc_features & EFX_FEATURE_FW_ASSISTED_TSO) ||
	    (!encp->enc_fw_assisted_tso_enabled))
		sc->tso_fw_assisted &= ~SFXGE_FATSOV1;
	if ((~encp->enc_features & EFX_FEATURE_FW_ASSISTED_TSO_V2) ||
	    (!encp->enc_fw_assisted_tso_v2_enabled))
		sc->tso_fw_assisted &= ~SFXGE_FATSOV2;

	sc->txqs_node = SYSCTL_ADD_NODE(
		device_get_sysctl_ctx(sc->dev),
		SYSCTL_CHILDREN(device_get_sysctl_tree(sc->dev)),
		OID_AUTO, "txq", CTLFLAG_RD, NULL, "Tx queues");
	if (sc->txqs_node == NULL) {
		rc = ENOMEM;
		goto fail_txq_node;
	}

	/* Initialize the transmit queues */
	if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_NON_CKSUM,
	    SFXGE_TXQ_NON_CKSUM, 0)) != 0)
		goto fail;

	if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_IP_CKSUM,
	    SFXGE_TXQ_IP_CKSUM, 0)) != 0)
		goto fail2;

	for (index = 0;
	     index < sc->txq_count - SFXGE_TXQ_NTYPES + 1;
	     index++) {
		if ((rc = sfxge_tx_qinit(sc, SFXGE_TXQ_NTYPES - 1 + index,
		    SFXGE_TXQ_IP_TCP_UDP_CKSUM, index)) != 0)
			goto fail3;
	}

	sfxge_tx_stat_init(sc);

	return (0);

fail3:
	while (--index >= 0)
		sfxge_tx_qfini(sc, SFXGE_TXQ_IP_TCP_UDP_CKSUM + index);

	sfxge_tx_qfini(sc, SFXGE_TXQ_IP_CKSUM);

fail2:
	sfxge_tx_qfini(sc, SFXGE_TXQ_NON_CKSUM);

fail:
fail_txq_node:
	sc->txq_count = 0;
	return (rc);
}