numam-dpdk/drivers/net/sfc/sfc_ef100_tx.c

/* SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright(c) 2019-2021 Xilinx, Inc.
 * Copyright(c) 2018-2019 Solarflare Communications Inc.
 *
 * This software was jointly developed between OKTET Labs (under contract
 * for Solarflare) and Solarflare Communications, Inc.
 */

#include <stdbool.h>

#include <rte_mbuf.h>
#include <rte_io.h>
#include <rte_net.h>

#include "efx.h"
#include "efx_types.h"
#include "efx_regs.h"
#include "efx_regs_ef100.h"

#include "sfc_debug.h"
#include "sfc_dp_tx.h"
#include "sfc_tweak.h"
#include "sfc_kvargs.h"
#include "sfc_ef100.h"


#define sfc_ef100_tx_err(_txq, ...) \
	SFC_DP_LOG(SFC_KVARG_DATAPATH_EF100, ERR, &(_txq)->dp.dpq, __VA_ARGS__)

#define sfc_ef100_tx_debug(_txq, ...) \
	SFC_DP_LOG(SFC_KVARG_DATAPATH_EF100, DEBUG, &(_txq)->dp.dpq, \
		   __VA_ARGS__)


/** Maximum length of the send descriptor data */
#define SFC_EF100_TX_SEND_DESC_LEN_MAX \
	((1u << ESF_GZ_TX_SEND_LEN_WIDTH) - 1)

/** Maximum length of the segment descriptor data */
#define SFC_EF100_TX_SEG_DESC_LEN_MAX \
	((1u << ESF_GZ_TX_SEG_LEN_WIDTH) - 1)

/**
 * Maximum number of descriptors/buffers in the Tx ring.
 * It should guarantee that corresponding event queue never overfill.
 * EF100 native datapath uses event queue of the same size as Tx queue.
 * Maximum number of events on datapath can be estimated as number of
 * Tx queue entries (one event per Tx buffer in the worst case) plus
 * Tx error and flush events.
 */
#define SFC_EF100_TXQ_LIMIT(_ndesc) \
	((_ndesc) - 1 /* head must not step on tail */ - \
	 1 /* Rx error */ - 1 /* flush */)

struct sfc_ef100_tx_sw_desc {
	struct rte_mbuf			*mbuf;
};

struct sfc_ef100_txq {
	unsigned int			flags;
#define SFC_EF100_TXQ_STARTED		0x1
#define SFC_EF100_TXQ_NOT_RUNNING	0x2
#define SFC_EF100_TXQ_EXCEPTION		0x4

	unsigned int			ptr_mask;
	unsigned int			added;
	unsigned int			completed;
	unsigned int			max_fill_level;
	unsigned int			free_thresh;
	struct sfc_ef100_tx_sw_desc	*sw_ring;
	efx_oword_t			*txq_hw_ring;
	volatile void			*doorbell;

	/* Completion/reap */
	unsigned int			evq_read_ptr;
	unsigned int			evq_phase_bit_shift;
	volatile efx_qword_t		*evq_hw_ring;

	uint16_t			tso_tcp_header_offset_limit;
	uint16_t			tso_max_nb_header_descs;
	uint16_t			tso_max_header_len;
	uint16_t			tso_max_nb_payload_descs;
	uint32_t			tso_max_payload_len;
	uint32_t			tso_max_nb_outgoing_frames;

	/* Datapath transmit queue anchor */
	struct sfc_dp_txq		dp;
};

static inline struct sfc_ef100_txq *
sfc_ef100_txq_by_dp_txq(struct sfc_dp_txq *dp_txq)
{
	return container_of(dp_txq, struct sfc_ef100_txq, dp);
}

static int
sfc_ef100_tx_prepare_pkt_tso(struct sfc_ef100_txq * const txq,
			     struct rte_mbuf *m)
{
	size_t header_len = ((m->ol_flags & PKT_TX_TUNNEL_MASK) ?
			     m->outer_l2_len + m->outer_l3_len : 0) +
			    m->l2_len + m->l3_len + m->l4_len;
	size_t payload_len = m->pkt_len - header_len;
	unsigned long mss_conformant_max_payload_len;
	unsigned int nb_payload_descs;

#ifdef RTE_LIBRTE_SFC_EFX_DEBUG
	switch (m->ol_flags & PKT_TX_TUNNEL_MASK) {
	case 0:
		/* FALLTHROUGH */
	case PKT_TX_TUNNEL_VXLAN:
		/* FALLTHROUGH */
	case PKT_TX_TUNNEL_GENEVE:
		break;
	default:
		return ENOTSUP;
	}
#endif

	mss_conformant_max_payload_len =
		m->tso_segsz * txq->tso_max_nb_outgoing_frames;

	/*
	 * Don't really want to know exact number of payload segments.
	 * Just use total number of segments as upper limit. Practically
	 * maximum number of payload segments is significantly bigger
	 * than maximum number header segments, so we can neglect header
	 * segments excluded total number of segments to estimate number
	 * of payload segments required.
	 */
	nb_payload_descs = m->nb_segs;

	/*
	 * Carry out multiple independent checks using bitwise OR
	 * to avoid unnecessary conditional branching.
	 */
	if (unlikely((header_len > txq->tso_max_header_len) |
		     (nb_payload_descs > txq->tso_max_nb_payload_descs) |
		     (payload_len > txq->tso_max_payload_len) |
		     (payload_len > mss_conformant_max_payload_len) |
		     (m->pkt_len == header_len)))
		return EINVAL;

	return 0;
}

static uint16_t
sfc_ef100_tx_prepare_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
			  uint16_t nb_pkts)
{
	struct sfc_ef100_txq * const txq = sfc_ef100_txq_by_dp_txq(tx_queue);
	uint16_t i;

	for (i = 0; i < nb_pkts; i++) {
		struct rte_mbuf *m = tx_pkts[i];
		unsigned int max_nb_header_segs = 0;
		bool calc_phdr_cksum = false;
		int ret;

		/*
		 * Partial checksum offload is used in the case of
		 * inner TCP/UDP checksum offload. It requires
		 * pseudo-header checksum which is calculated below,
		 * but requires contiguous packet headers.
		 */
		if ((m->ol_flags & PKT_TX_TUNNEL_MASK) &&
		    (m->ol_flags & PKT_TX_L4_MASK)) {
			calc_phdr_cksum = true;
			max_nb_header_segs = 1;
		} else if (m->ol_flags & PKT_TX_TCP_SEG) {
			max_nb_header_segs = txq->tso_max_nb_header_descs;
		}

		ret = sfc_dp_tx_prepare_pkt(m, max_nb_header_segs, 0,
					    txq->tso_tcp_header_offset_limit,
					    txq->max_fill_level, 1, 0);
		if (unlikely(ret != 0)) {
			rte_errno = ret;
			break;
		}

		if (m->ol_flags & PKT_TX_TCP_SEG) {
			ret = sfc_ef100_tx_prepare_pkt_tso(txq, m);
			if (unlikely(ret != 0)) {
				rte_errno = ret;
				break;
			}
		} else if (m->nb_segs > EFX_MASK32(ESF_GZ_TX_SEND_NUM_SEGS)) {
			rte_errno = EINVAL;
			break;
		}

		if (calc_phdr_cksum) {
			/*
			 * Full checksum offload does IPv4 header checksum
			 * and does not require any assistance.
			 */
			ret = rte_net_intel_cksum_flags_prepare(m,
					m->ol_flags & ~PKT_TX_IP_CKSUM);
			if (unlikely(ret != 0)) {
				rte_errno = -ret;
				break;
			}
		}
	}

	return i;
}

static bool
sfc_ef100_tx_get_event(struct sfc_ef100_txq *txq, efx_qword_t *ev)
{
	volatile efx_qword_t *evq_hw_ring = txq->evq_hw_ring;

	/*
	 * Exception flag is set when reap is done.
	 * It is never done twice per packet burst get, and absence of
	 * the flag is checked on burst get entry.
	 */
	SFC_ASSERT((txq->flags & SFC_EF100_TXQ_EXCEPTION) == 0);

	*ev = evq_hw_ring[txq->evq_read_ptr & txq->ptr_mask];

	if (!sfc_ef100_ev_present(ev,
			(txq->evq_read_ptr >> txq->evq_phase_bit_shift) & 1))
		return false;

	if (unlikely(!sfc_ef100_ev_type_is(ev,
					   ESE_GZ_EF100_EV_TX_COMPLETION))) {
		/*
		 * Do not move read_ptr to keep the event for exception
		 * handling by the control path.
		 */
		txq->flags |= SFC_EF100_TXQ_EXCEPTION;
		sfc_ef100_tx_err(txq,
			"TxQ exception at EvQ ptr %u(%#x), event %08x:%08x",
			txq->evq_read_ptr, txq->evq_read_ptr & txq->ptr_mask,
			EFX_QWORD_FIELD(*ev, EFX_DWORD_1),
			EFX_QWORD_FIELD(*ev, EFX_DWORD_0));
		return false;
	}

	sfc_ef100_tx_debug(txq, "TxQ got event %08x:%08x at %u (%#x)",
			   EFX_QWORD_FIELD(*ev, EFX_DWORD_1),
			   EFX_QWORD_FIELD(*ev, EFX_DWORD_0),
			   txq->evq_read_ptr,
			   txq->evq_read_ptr & txq->ptr_mask);

	txq->evq_read_ptr++;
	return true;
}

static unsigned int
sfc_ef100_tx_process_events(struct sfc_ef100_txq *txq)
{
	unsigned int num_descs = 0;
	efx_qword_t tx_ev;

	while (sfc_ef100_tx_get_event(txq, &tx_ev))
		num_descs += EFX_QWORD_FIELD(tx_ev, ESF_GZ_EV_TXCMPL_NUM_DESC);

	return num_descs;
}

static void
sfc_ef100_tx_reap_num_descs(struct sfc_ef100_txq *txq, unsigned int num_descs)
{
	if (num_descs > 0) {
		unsigned int completed = txq->completed;
		unsigned int pending = completed + num_descs;
		struct rte_mbuf *bulk[SFC_TX_REAP_BULK_SIZE];
		unsigned int nb = 0;

		do {
			struct sfc_ef100_tx_sw_desc *txd;
			struct rte_mbuf *m;

			txd = &txq->sw_ring[completed & txq->ptr_mask];
			if (txd->mbuf == NULL)
				continue;

			m = rte_pktmbuf_prefree_seg(txd->mbuf);
			if (m == NULL)
				continue;

			txd->mbuf = NULL;

			if (nb == RTE_DIM(bulk) ||
			    (nb != 0 && m->pool != bulk[0]->pool)) {
				rte_mempool_put_bulk(bulk[0]->pool,
						     (void *)bulk, nb);
				nb = 0;
			}

			bulk[nb++] = m;
		} while (++completed != pending);

		if (nb != 0)
			rte_mempool_put_bulk(bulk[0]->pool, (void *)bulk, nb);

		txq->completed = completed;
	}
}

static void
sfc_ef100_tx_reap(struct sfc_ef100_txq *txq)
{
	sfc_ef100_tx_reap_num_descs(txq, sfc_ef100_tx_process_events(txq));
}

static uint8_t
sfc_ef100_tx_qdesc_cso_inner_l3(uint64_t tx_tunnel)
{
	uint8_t inner_l3;

	switch (tx_tunnel) {
	case PKT_TX_TUNNEL_VXLAN:
		inner_l3 = ESE_GZ_TX_DESC_CS_INNER_L3_VXLAN;
		break;
	case PKT_TX_TUNNEL_GENEVE:
		inner_l3 = ESE_GZ_TX_DESC_CS_INNER_L3_GENEVE;
		break;
	default:
		inner_l3 = ESE_GZ_TX_DESC_CS_INNER_L3_OFF;
		break;
	}
	return inner_l3;
}

static void
sfc_ef100_tx_qdesc_send_create(const struct rte_mbuf *m, efx_oword_t *tx_desc)
{
	bool outer_l3;
	bool outer_l4;
	uint8_t inner_l3;
	uint8_t partial_en;
	uint16_t part_cksum_w;
	uint16_t l4_offset_w;

	if ((m->ol_flags & PKT_TX_TUNNEL_MASK) == 0) {
		outer_l3 = (m->ol_flags & PKT_TX_IP_CKSUM);
		outer_l4 = (m->ol_flags & PKT_TX_L4_MASK);
		inner_l3 = ESE_GZ_TX_DESC_CS_INNER_L3_OFF;
		partial_en = ESE_GZ_TX_DESC_CSO_PARTIAL_EN_OFF;
		part_cksum_w = 0;
		l4_offset_w = 0;
	} else {
		outer_l3 = (m->ol_flags & PKT_TX_OUTER_IP_CKSUM);
		outer_l4 = (m->ol_flags & PKT_TX_OUTER_UDP_CKSUM);
		inner_l3 = sfc_ef100_tx_qdesc_cso_inner_l3(m->ol_flags &
							   PKT_TX_TUNNEL_MASK);

		switch (m->ol_flags & PKT_TX_L4_MASK) {
		case PKT_TX_TCP_CKSUM:
			partial_en = ESE_GZ_TX_DESC_CSO_PARTIAL_EN_TCP;
			part_cksum_w = offsetof(struct rte_tcp_hdr, cksum) >> 1;
			break;
		case PKT_TX_UDP_CKSUM:
			partial_en = ESE_GZ_TX_DESC_CSO_PARTIAL_EN_UDP;
			part_cksum_w = offsetof(struct rte_udp_hdr,
						dgram_cksum) >> 1;
			break;
		default:
			partial_en = ESE_GZ_TX_DESC_CSO_PARTIAL_EN_OFF;
			part_cksum_w = 0;
			break;
		}
		l4_offset_w = (m->outer_l2_len + m->outer_l3_len +
				m->l2_len + m->l3_len) >> 1;
	}

	EFX_POPULATE_OWORD_10(*tx_desc,
			ESF_GZ_TX_SEND_ADDR, rte_mbuf_data_iova(m),
			ESF_GZ_TX_SEND_LEN, rte_pktmbuf_data_len(m),
			ESF_GZ_TX_SEND_NUM_SEGS, m->nb_segs,
			ESF_GZ_TX_SEND_CSO_PARTIAL_START_W, l4_offset_w,
			ESF_GZ_TX_SEND_CSO_PARTIAL_CSUM_W, part_cksum_w,
			ESF_GZ_TX_SEND_CSO_PARTIAL_EN, partial_en,
			ESF_GZ_TX_SEND_CSO_INNER_L3, inner_l3,
			ESF_GZ_TX_SEND_CSO_OUTER_L3, outer_l3,
			ESF_GZ_TX_SEND_CSO_OUTER_L4, outer_l4,
			ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_SEND);

	if (m->ol_flags & PKT_TX_VLAN_PKT) {
		efx_oword_t tx_desc_extra_fields;

		EFX_POPULATE_OWORD_2(tx_desc_extra_fields,
				ESF_GZ_TX_SEND_VLAN_INSERT_EN, 1,
				ESF_GZ_TX_SEND_VLAN_INSERT_TCI, m->vlan_tci);

		EFX_OR_OWORD(*tx_desc, tx_desc_extra_fields);
	}
}

static void
sfc_ef100_tx_qdesc_seg_create(rte_iova_t addr, uint16_t len,
			      efx_oword_t *tx_desc)
{
	EFX_POPULATE_OWORD_3(*tx_desc,
			ESF_GZ_TX_SEG_ADDR, addr,
			ESF_GZ_TX_SEG_LEN, len,
			ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_SEG);
}

static void
sfc_ef100_tx_qdesc_tso_create(const struct rte_mbuf *m,
			      uint16_t nb_header_descs,
			      uint16_t nb_payload_descs,
			      size_t header_len, size_t payload_len,
			      size_t outer_iph_off, size_t outer_udph_off,
			      size_t iph_off, size_t tcph_off,
			      efx_oword_t *tx_desc)
{
	efx_oword_t tx_desc_extra_fields;
	int ed_outer_udp_len = (outer_udph_off != 0) ? 1 : 0;
	int ed_outer_ip_len = (outer_iph_off != 0) ? 1 : 0;
	int ed_outer_ip_id = (outer_iph_off != 0) ?
		ESE_GZ_TX_DESC_IP4_ID_INC_MOD16 : 0;
	/*
	 * If no tunnel encapsulation is present, then the ED_INNER
	 * fields should be used.
	 */
	int ed_inner_ip_id = ESE_GZ_TX_DESC_IP4_ID_INC_MOD16;
	uint8_t inner_l3 = sfc_ef100_tx_qdesc_cso_inner_l3(
					m->ol_flags & PKT_TX_TUNNEL_MASK);

	EFX_POPULATE_OWORD_10(*tx_desc,
			ESF_GZ_TX_TSO_MSS, m->tso_segsz,
			ESF_GZ_TX_TSO_HDR_NUM_SEGS, nb_header_descs,
			ESF_GZ_TX_TSO_PAYLOAD_NUM_SEGS, nb_payload_descs,
			ESF_GZ_TX_TSO_ED_OUTER_IP4_ID, ed_outer_ip_id,
			ESF_GZ_TX_TSO_ED_INNER_IP4_ID, ed_inner_ip_id,
			ESF_GZ_TX_TSO_ED_OUTER_IP_LEN, ed_outer_ip_len,
			ESF_GZ_TX_TSO_ED_INNER_IP_LEN, 1,
			ESF_GZ_TX_TSO_ED_OUTER_UDP_LEN, ed_outer_udp_len,
			ESF_GZ_TX_TSO_HDR_LEN_W, header_len >> 1,
			ESF_GZ_TX_TSO_PAYLOAD_LEN, payload_len);

	EFX_POPULATE_OWORD_9(tx_desc_extra_fields,
			/*
			 * Outer offsets are required for outer IPv4 ID
			 * and length edits in the case of tunnel TSO.
			 */
			ESF_GZ_TX_TSO_OUTER_L3_OFF_W, outer_iph_off >> 1,
			ESF_GZ_TX_TSO_OUTER_L4_OFF_W, outer_udph_off >> 1,
			/*
			 * Inner offsets are required for inner IPv4 ID
			 * and IP length edits and partial checksum
			 * offload in the case of tunnel TSO.
			 */
			ESF_GZ_TX_TSO_INNER_L3_OFF_W, iph_off >> 1,
			ESF_GZ_TX_TSO_INNER_L4_OFF_W, tcph_off >> 1,
			ESF_GZ_TX_TSO_CSO_INNER_L4,
				inner_l3 != ESE_GZ_TX_DESC_CS_INNER_L3_OFF,
			ESF_GZ_TX_TSO_CSO_INNER_L3, inner_l3,
			/*
			 * Use outer full checksum offloads which do
			 * not require any extra information.
			 */
			ESF_GZ_TX_TSO_CSO_OUTER_L3, 1,
			ESF_GZ_TX_TSO_CSO_OUTER_L4, 1,
			ESF_GZ_TX_DESC_TYPE, ESE_GZ_TX_DESC_TYPE_TSO);

	EFX_OR_OWORD(*tx_desc, tx_desc_extra_fields);

	if (m->ol_flags & PKT_TX_VLAN_PKT) {
		EFX_POPULATE_OWORD_2(tx_desc_extra_fields,
				ESF_GZ_TX_TSO_VLAN_INSERT_EN, 1,
				ESF_GZ_TX_TSO_VLAN_INSERT_TCI, m->vlan_tci);

		EFX_OR_OWORD(*tx_desc, tx_desc_extra_fields);
	}
}

static inline void
sfc_ef100_tx_qpush(struct sfc_ef100_txq *txq, unsigned int added)
{
	efx_dword_t dword;

	EFX_POPULATE_DWORD_1(dword, ERF_GZ_TX_RING_PIDX, added & txq->ptr_mask);

	/* DMA sync to device is not required */

	/*
	 * rte_write32() has rte_io_wmb() which guarantees that the STORE
	 * operations (i.e. Rx and event descriptor updates) that precede
	 * the rte_io_wmb() call are visible to NIC before the STORE
	 * operations that follow it (i.e. doorbell write).
	 */
	rte_write32(dword.ed_u32[0], txq->doorbell);

	sfc_ef100_tx_debug(txq, "TxQ pushed doorbell at pidx %u (added=%u)",
			   EFX_DWORD_FIELD(dword, ERF_GZ_TX_RING_PIDX),
			   added);
}

static unsigned int
sfc_ef100_tx_pkt_descs_max(const struct rte_mbuf *m)
{
	unsigned int extra_descs = 0;

/** Maximum length of an mbuf segment data */
#define SFC_MBUF_SEG_LEN_MAX		UINT16_MAX
	RTE_BUILD_BUG_ON(sizeof(m->data_len) != 2);

	if (m->ol_flags & PKT_TX_TCP_SEG) {
		/* Tx TSO descriptor */
		extra_descs++;
		/*
		 * Extra Tx segment descriptor may be required if header
		 * ends in the middle of segment.
		 */
		extra_descs++;
	} else {
		/*
		 * mbuf segment cannot be bigger than maximum segment length
		 * and maximum packet length since TSO is not supported yet.
		 * Make sure that the first segment does not need fragmentation
		 * (split into many Tx descriptors).
		 */
		RTE_BUILD_BUG_ON(SFC_EF100_TX_SEND_DESC_LEN_MAX <
				 RTE_MIN((unsigned int)EFX_MAC_PDU_MAX,
				 SFC_MBUF_SEG_LEN_MAX));
	}

	/*
	 * Any segment of scattered packet cannot be bigger than maximum
	 * segment length. Make sure that subsequent segments do not need
	 * fragmentation (split into many Tx descriptors).
	 */
	RTE_BUILD_BUG_ON(SFC_EF100_TX_SEG_DESC_LEN_MAX < SFC_MBUF_SEG_LEN_MAX);

	return m->nb_segs + extra_descs;
}

static struct rte_mbuf *
sfc_ef100_xmit_tso_pkt(struct sfc_ef100_txq * const txq,
		       struct rte_mbuf *m, unsigned int *added)
{
	struct rte_mbuf *m_seg = m;
	unsigned int nb_hdr_descs;
	unsigned int nb_pld_descs;
	unsigned int seg_split = 0;
	unsigned int tso_desc_id;
	unsigned int id;
	size_t outer_iph_off;
	size_t outer_udph_off;
	size_t iph_off;
	size_t tcph_off;
	size_t header_len;
	size_t remaining_hdr_len;

	if (m->ol_flags & PKT_TX_TUNNEL_MASK) {
		outer_iph_off = m->outer_l2_len;
		outer_udph_off = outer_iph_off + m->outer_l3_len;
	} else {
		outer_iph_off = 0;
		outer_udph_off = 0;
	}
	iph_off = outer_udph_off + m->l2_len;
	tcph_off = iph_off + m->l3_len;
	header_len = tcph_off + m->l4_len;

	/*
	 * Remember ID of the TX_TSO descriptor to be filled in.
	 * We can't fill it in right now since we need to calculate
	 * number of header and payload segments first and don't want
	 * to traverse it twice here.
	 */
	tso_desc_id = (*added)++ & txq->ptr_mask;

	remaining_hdr_len = header_len;
	do {
		id = (*added)++ & txq->ptr_mask;
		if (rte_pktmbuf_data_len(m_seg) <= remaining_hdr_len) {
			/* The segment is fully header segment */
			sfc_ef100_tx_qdesc_seg_create(
				rte_mbuf_data_iova(m_seg),
				rte_pktmbuf_data_len(m_seg),
				&txq->txq_hw_ring[id]);
			remaining_hdr_len -= rte_pktmbuf_data_len(m_seg);
		} else {
			/*
			 * The segment must be split into header and
			 * payload segments
			 */
			sfc_ef100_tx_qdesc_seg_create(
				rte_mbuf_data_iova(m_seg),
				remaining_hdr_len,
				&txq->txq_hw_ring[id]);
			SFC_ASSERT(txq->sw_ring[id].mbuf == NULL);

			id = (*added)++ & txq->ptr_mask;
			sfc_ef100_tx_qdesc_seg_create(
				rte_mbuf_data_iova(m_seg) + remaining_hdr_len,
				rte_pktmbuf_data_len(m_seg) - remaining_hdr_len,
				&txq->txq_hw_ring[id]);
			remaining_hdr_len = 0;
			seg_split = 1;
		}
		txq->sw_ring[id].mbuf = m_seg;
		m_seg = m_seg->next;
	} while (remaining_hdr_len > 0);

	/*
	 * If a segment is split into header and payload segments, added
	 * pointer counts it twice and we should correct it.
	 */
	nb_hdr_descs = ((id - tso_desc_id) & txq->ptr_mask) - seg_split;
	nb_pld_descs = m->nb_segs - nb_hdr_descs + seg_split;

	sfc_ef100_tx_qdesc_tso_create(m, nb_hdr_descs, nb_pld_descs, header_len,
				      rte_pktmbuf_pkt_len(m) - header_len,
				      outer_iph_off, outer_udph_off,
				      iph_off, tcph_off,
				      &txq->txq_hw_ring[tso_desc_id]);

	return m_seg;
}

static uint16_t
sfc_ef100_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts)
{
	struct sfc_ef100_txq * const txq = sfc_ef100_txq_by_dp_txq(tx_queue);
	unsigned int added;
	unsigned int dma_desc_space;
	bool reap_done;
	struct rte_mbuf **pktp;
	struct rte_mbuf **pktp_end;

	if (unlikely(txq->flags &
		     (SFC_EF100_TXQ_NOT_RUNNING | SFC_EF100_TXQ_EXCEPTION)))
		return 0;

	added = txq->added;
	dma_desc_space = txq->max_fill_level - (added - txq->completed);

	reap_done = (dma_desc_space < txq->free_thresh);
	if (reap_done) {
		sfc_ef100_tx_reap(txq);
		dma_desc_space = txq->max_fill_level - (added - txq->completed);
	}

	for (pktp = &tx_pkts[0], pktp_end = &tx_pkts[nb_pkts];
	     pktp != pktp_end;
	     ++pktp) {
		struct rte_mbuf *m_seg = *pktp;
		unsigned int pkt_start = added;
		unsigned int id;

		if (likely(pktp + 1 != pktp_end))
			rte_mbuf_prefetch_part1(pktp[1]);

		if (sfc_ef100_tx_pkt_descs_max(m_seg) > dma_desc_space) {
			if (reap_done)
				break;

			/* Push already prepared descriptors before polling */
			if (added != txq->added) {
				sfc_ef100_tx_qpush(txq, added);
				txq->added = added;
			}

			sfc_ef100_tx_reap(txq);
			reap_done = true;
			dma_desc_space = txq->max_fill_level -
				(added - txq->completed);
			if (sfc_ef100_tx_pkt_descs_max(m_seg) > dma_desc_space)
				break;
		}

		if (m_seg->ol_flags & PKT_TX_TCP_SEG) {
			m_seg = sfc_ef100_xmit_tso_pkt(txq, m_seg, &added);
		} else {
			id = added++ & txq->ptr_mask;
			sfc_ef100_tx_qdesc_send_create(m_seg,
						       &txq->txq_hw_ring[id]);

			/*
			 * rte_pktmbuf_free() is commonly used in DPDK for
			 * recycling packets - the function checks every
			 * segment's reference counter and returns the
			 * buffer to its pool whenever possible;
			 * nevertheless, freeing mbuf segments one by one
			 * may entail some performance decline;
			 * from this point, sfc_efx_tx_reap() does the same job
			 * on its own and frees buffers in bulks (all mbufs
			 * within a bulk belong to the same pool);
			 * from this perspective, individual segment pointers
			 * must be associated with the corresponding SW
			 * descriptors independently so that only one loop
			 * is sufficient on reap to inspect all the buffers
			 */
			txq->sw_ring[id].mbuf = m_seg;
			m_seg = m_seg->next;
		}

		while (m_seg != NULL) {
			RTE_BUILD_BUG_ON(SFC_MBUF_SEG_LEN_MAX >
					 SFC_EF100_TX_SEG_DESC_LEN_MAX);

			id = added++ & txq->ptr_mask;
			sfc_ef100_tx_qdesc_seg_create(rte_mbuf_data_iova(m_seg),
					rte_pktmbuf_data_len(m_seg),
					&txq->txq_hw_ring[id]);
			txq->sw_ring[id].mbuf = m_seg;
			m_seg = m_seg->next;
		}

		dma_desc_space -= (added - pkt_start);
	}

	if (likely(added != txq->added)) {
		sfc_ef100_tx_qpush(txq, added);
		txq->added = added;
	}

#if SFC_TX_XMIT_PKTS_REAP_AT_LEAST_ONCE
	if (!reap_done)
		sfc_ef100_tx_reap(txq);
#endif

	return pktp - &tx_pkts[0];
}

static sfc_dp_tx_get_dev_info_t sfc_ef100_get_dev_info;
static void
sfc_ef100_get_dev_info(struct rte_eth_dev_info *dev_info)
{
	/*
	 * Number of descriptors just defines maximum number of pushed
	 * descriptors (fill level).
	 */
	dev_info->tx_desc_lim.nb_min = 1;
	dev_info->tx_desc_lim.nb_align = 1;
}

static sfc_dp_tx_qsize_up_rings_t sfc_ef100_tx_qsize_up_rings;
static int
sfc_ef100_tx_qsize_up_rings(uint16_t nb_tx_desc,
			   struct sfc_dp_tx_hw_limits *limits,
			   unsigned int *txq_entries,
			   unsigned int *evq_entries,
			   unsigned int *txq_max_fill_level)
{
	/*
	 * rte_ethdev API guarantees that the number meets min, max and
	 * alignment requirements.
	 */
	if (nb_tx_desc <= limits->txq_min_entries)
		*txq_entries = limits->txq_min_entries;
	else
		*txq_entries = rte_align32pow2(nb_tx_desc);

	*evq_entries = *txq_entries;

	*txq_max_fill_level = RTE_MIN(nb_tx_desc,
				      SFC_EF100_TXQ_LIMIT(*evq_entries));
	return 0;
}

static sfc_dp_tx_qcreate_t sfc_ef100_tx_qcreate;
static int
sfc_ef100_tx_qcreate(uint16_t port_id, uint16_t queue_id,
		    const struct rte_pci_addr *pci_addr, int socket_id,
		    const struct sfc_dp_tx_qcreate_info *info,
		    struct sfc_dp_txq **dp_txqp)
{
	struct sfc_ef100_txq *txq;
	int rc;

	rc = EINVAL;
	if (info->txq_entries != info->evq_entries)
		goto fail_bad_args;

	rc = ENOMEM;
	txq = rte_zmalloc_socket("sfc-ef100-txq", sizeof(*txq),
				 RTE_CACHE_LINE_SIZE, socket_id);
	if (txq == NULL)
		goto fail_txq_alloc;

	sfc_dp_queue_init(&txq->dp.dpq, port_id, queue_id, pci_addr);

	rc = ENOMEM;
	txq->sw_ring = rte_calloc_socket("sfc-ef100-txq-sw_ring",
					 info->txq_entries,
					 sizeof(*txq->sw_ring),
					 RTE_CACHE_LINE_SIZE, socket_id);
	if (txq->sw_ring == NULL)
		goto fail_sw_ring_alloc;

	txq->flags = SFC_EF100_TXQ_NOT_RUNNING;
	txq->ptr_mask = info->txq_entries - 1;
	txq->max_fill_level = info->max_fill_level;
	txq->free_thresh = info->free_thresh;
	txq->evq_phase_bit_shift = rte_bsf32(info->evq_entries);
	txq->txq_hw_ring = info->txq_hw_ring;
	txq->doorbell = (volatile uint8_t *)info->mem_bar +
			ER_GZ_TX_RING_DOORBELL_OFST +
			(info->hw_index << info->vi_window_shift);
	txq->evq_hw_ring = info->evq_hw_ring;

	txq->tso_tcp_header_offset_limit = info->tso_tcp_header_offset_limit;
	txq->tso_max_nb_header_descs = info->tso_max_nb_header_descs;
	txq->tso_max_header_len = info->tso_max_header_len;
	txq->tso_max_nb_payload_descs = info->tso_max_nb_payload_descs;
	txq->tso_max_payload_len = info->tso_max_payload_len;
	txq->tso_max_nb_outgoing_frames = info->tso_max_nb_outgoing_frames;

	sfc_ef100_tx_debug(txq, "TxQ doorbell is %p", txq->doorbell);

	*dp_txqp = &txq->dp;
	return 0;

fail_sw_ring_alloc:
	rte_free(txq);

fail_txq_alloc:
fail_bad_args:
	return rc;
}

static sfc_dp_tx_qdestroy_t sfc_ef100_tx_qdestroy;
static void
sfc_ef100_tx_qdestroy(struct sfc_dp_txq *dp_txq)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);

	rte_free(txq->sw_ring);
	rte_free(txq);
}

static sfc_dp_tx_qstart_t sfc_ef100_tx_qstart;
static int
sfc_ef100_tx_qstart(struct sfc_dp_txq *dp_txq, unsigned int evq_read_ptr,
		   unsigned int txq_desc_index)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);

	txq->evq_read_ptr = evq_read_ptr;
	txq->added = txq->completed = txq_desc_index;

	txq->flags |= SFC_EF100_TXQ_STARTED;
	txq->flags &= ~(SFC_EF100_TXQ_NOT_RUNNING | SFC_EF100_TXQ_EXCEPTION);

	return 0;
}

static sfc_dp_tx_qstop_t sfc_ef100_tx_qstop;
static void
sfc_ef100_tx_qstop(struct sfc_dp_txq *dp_txq, unsigned int *evq_read_ptr)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);

	txq->flags |= SFC_EF100_TXQ_NOT_RUNNING;

	*evq_read_ptr = txq->evq_read_ptr;
}

static sfc_dp_tx_qtx_ev_t sfc_ef100_tx_qtx_ev;
static bool
sfc_ef100_tx_qtx_ev(struct sfc_dp_txq *dp_txq, unsigned int num_descs)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);

	SFC_ASSERT(txq->flags & SFC_EF100_TXQ_NOT_RUNNING);

	sfc_ef100_tx_reap_num_descs(txq, num_descs);

	return false;
}

static sfc_dp_tx_qreap_t sfc_ef100_tx_qreap;
static void
sfc_ef100_tx_qreap(struct sfc_dp_txq *dp_txq)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);
	unsigned int completed;

	for (completed = txq->completed; completed != txq->added; ++completed) {
		struct sfc_ef100_tx_sw_desc *txd;

		txd = &txq->sw_ring[completed & txq->ptr_mask];
		if (txd->mbuf != NULL) {
			rte_pktmbuf_free_seg(txd->mbuf);
			txd->mbuf = NULL;
		}
	}

	txq->flags &= ~SFC_EF100_TXQ_STARTED;
}

static unsigned int
sfc_ef100_tx_qdesc_npending(struct sfc_ef100_txq *txq)
{
	const unsigned int evq_old_read_ptr = txq->evq_read_ptr;
	unsigned int npending = 0;
	efx_qword_t tx_ev;

	if (unlikely(txq->flags &
		     (SFC_EF100_TXQ_NOT_RUNNING | SFC_EF100_TXQ_EXCEPTION)))
		return 0;

	while (sfc_ef100_tx_get_event(txq, &tx_ev))
		npending += EFX_QWORD_FIELD(tx_ev, ESF_GZ_EV_TXCMPL_NUM_DESC);

	/*
	 * The function does not process events, so return event queue read
	 * pointer to the original position to allow the events that were
	 * read to be processed later
	 */
	txq->evq_read_ptr = evq_old_read_ptr;

	return npending;
}

static sfc_dp_tx_qdesc_status_t sfc_ef100_tx_qdesc_status;
static int
sfc_ef100_tx_qdesc_status(struct sfc_dp_txq *dp_txq, uint16_t offset)
{
	struct sfc_ef100_txq *txq = sfc_ef100_txq_by_dp_txq(dp_txq);
	unsigned int pushed = txq->added - txq->completed;

	if (unlikely(offset > txq->ptr_mask))
		return -EINVAL;

	if (unlikely(offset >= txq->max_fill_level))
		return RTE_ETH_TX_DESC_UNAVAIL;

	return (offset >= pushed ||
		offset < sfc_ef100_tx_qdesc_npending(txq)) ?
		RTE_ETH_TX_DESC_DONE : RTE_ETH_TX_DESC_FULL;
}

struct sfc_dp_tx sfc_ef100_tx = {
	.dp = {
		.name		= SFC_KVARG_DATAPATH_EF100,
		.type		= SFC_DP_TX,
		.hw_fw_caps	= SFC_DP_HW_FW_CAP_EF100,
	},
	.features		= SFC_DP_TX_FEAT_MULTI_PROCESS,
	.dev_offload_capa	= 0,
	.queue_offload_capa	= DEV_TX_OFFLOAD_VLAN_INSERT |
				  DEV_TX_OFFLOAD_IPV4_CKSUM |
				  DEV_TX_OFFLOAD_OUTER_IPV4_CKSUM |
				  DEV_TX_OFFLOAD_OUTER_UDP_CKSUM |
				  DEV_TX_OFFLOAD_UDP_CKSUM |
				  DEV_TX_OFFLOAD_TCP_CKSUM |
				  DEV_TX_OFFLOAD_MULTI_SEGS |
				  DEV_TX_OFFLOAD_TCP_TSO |
				  DEV_TX_OFFLOAD_VXLAN_TNL_TSO |
				  DEV_TX_OFFLOAD_GENEVE_TNL_TSO,
	.get_dev_info		= sfc_ef100_get_dev_info,
	.qsize_up_rings		= sfc_ef100_tx_qsize_up_rings,
	.qcreate		= sfc_ef100_tx_qcreate,
	.qdestroy		= sfc_ef100_tx_qdestroy,
	.qstart			= sfc_ef100_tx_qstart,
	.qtx_ev			= sfc_ef100_tx_qtx_ev,
	.qstop			= sfc_ef100_tx_qstop,
	.qreap			= sfc_ef100_tx_qreap,
	.qdesc_status		= sfc_ef100_tx_qdesc_status,
	.pkt_prepare		= sfc_ef100_tx_prepare_pkts,
	.pkt_burst		= sfc_ef100_xmit_pkts,
};