Initial file dump from open source releaseHEADmaster

1 files changed, 1103 insertions, 0 deletions

diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
new file mode 100644
index 00000000..5e090e54
--- /dev/null
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -0,0 +1,1103 @@
+/****************************************************************************
+ * Driver for Solarflare Solarstorm network controllers and boards
+ * Copyright 2005-2006 Fen Systems Ltd.
+ * Copyright 2005-2010 Solarflare Communications Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation, incorporated herein by reference.
+ */
+
+#include <linux/pci.h>
+#include <linux/tcp.h>
+#include <linux/ip.h>
+#include <linux/in.h>
+#include <linux/ipv6.h>
+#include <linux/slab.h>
+#include <net/ipv6.h>
+#include <linux/if_ether.h>
+#include <linux/highmem.h>
+#include "net_driver.h"
+#include "efx.h"
+#include "nic.h"
+#include "workarounds.h"
+
+static void efx_dequeue_buffer(struct efx_tx_queue *tx_queue,
+			       struct efx_tx_buffer *buffer,
+			       unsigned int *pkts_compl,
+			       unsigned int *bytes_compl)
+{
+	if (buffer->unmap_len) {
+		struct device *dma_dev = &tx_queue->efx->pci_dev->dev;
+		dma_addr_t unmap_addr = (buffer->dma_addr + buffer->len -
+					 buffer->unmap_len);
+		if (buffer->flags & EFX_TX_BUF_MAP_SINGLE)
+			dma_unmap_single(dma_dev, unmap_addr, buffer->unmap_len,
+					 DMA_TO_DEVICE);
+		else
+			dma_unmap_page(dma_dev, unmap_addr, buffer->unmap_len,
+				       DMA_TO_DEVICE);
+		buffer->unmap_len = 0;
+	}
+
+	if (buffer->flags & EFX_TX_BUF_SKB) {
+		(*pkts_compl)++;
+		(*bytes_compl) += buffer->skb->len;
+		dev_kfree_skb_any((struct sk_buff *) buffer->skb);
+		netif_vdbg(tx_queue->efx, tx_done, tx_queue->efx->net_dev,
+			   "TX queue %d transmission id %x complete\n",
+			   tx_queue->queue, tx_queue->read_count);
+	} else if (buffer->flags & EFX_TX_BUF_HEAP) {
+		kfree(buffer->heap_buf);
+	}
+
+	buffer->len = 0;
+	buffer->flags = 0;
+}
+
+static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
+			       struct sk_buff *skb);
+
+static inline unsigned
+efx_max_tx_len(struct efx_nic *efx, dma_addr_t dma_addr)
+{
+	/* Depending on the NIC revision, we can use descriptor
+	 * lengths up to 8K or 8K-1.  However, since PCI Express
+	 * devices must split read requests at 4K boundaries, there is
+	 * little benefit from using descriptors that cross those
+	 * boundaries and we keep things simple by not doing so.
+	 */
+	unsigned len = (~dma_addr & (EFX_PAGE_SIZE - 1)) + 1;
+
+	/* Work around hardware bug for unaligned buffers. */
+	if (EFX_WORKAROUND_5391(efx) && (dma_addr & 0xf))
+		len = min_t(unsigned, len, 512 - (dma_addr & 0xf));
+
+	return len;
+}
+
+unsigned int efx_tx_max_skb_descs(struct efx_nic *efx)
+{
+	/* Header and payload descriptor for each output segment, plus
+	 * one for every input fragment boundary within a segment
+	 */
+	unsigned int max_descs = EFX_TSO_MAX_SEGS * 2 + MAX_SKB_FRAGS;
+
+	/* Possibly one more per segment for the alignment workaround */
+	if (EFX_WORKAROUND_5391(efx))
+		max_descs += EFX_TSO_MAX_SEGS;
+
+	/* Possibly more for PCIe page boundaries within input fragments */
+	if (PAGE_SIZE > EFX_PAGE_SIZE)
+		max_descs += max_t(unsigned int, MAX_SKB_FRAGS,
+				   DIV_ROUND_UP(GSO_MAX_SIZE, EFX_PAGE_SIZE));
+
+	return max_descs;
+}
+
+/* Get partner of a TX queue, seen as part of the same net core queue */
+static struct efx_tx_queue *efx_tx_queue_partner(struct efx_tx_queue *tx_queue)
+{
+	if (tx_queue->queue & EFX_TXQ_TYPE_OFFLOAD)
+		return tx_queue - EFX_TXQ_TYPE_OFFLOAD;
+	else
+		return tx_queue + EFX_TXQ_TYPE_OFFLOAD;
+}
+
+static void efx_tx_maybe_stop_queue(struct efx_tx_queue *txq1)
+{
+	/* We need to consider both queues that the net core sees as one */
+	struct efx_tx_queue *txq2 = efx_tx_queue_partner(txq1);
+	struct efx_nic *efx = txq1->efx;
+	unsigned int fill_level;
+
+	fill_level = max(txq1->insert_count - txq1->old_read_count,
+			 txq2->insert_count - txq2->old_read_count);
+	if (likely(fill_level < efx->txq_stop_thresh))
+		return;
+
+	/* We used the stale old_read_count above, which gives us a
+	 * pessimistic estimate of the fill level (which may even
+	 * validly be >= efx->txq_entries).  Now try again using
+	 * read_count (more likely to be a cache miss).
+	 *
+	 * If we read read_count and then conditionally stop the
+	 * queue, it is possible for the completion path to race with
+	 * us and complete all outstanding descriptors in the middle,
+	 * after which there will be no more completions to wake it.
+	 * Therefore we stop the queue first, then read read_count
+	 * (with a memory barrier to ensure the ordering), then
+	 * restart the queue if the fill level turns out to be low
+	 * enough.
+	 */
+	netif_tx_stop_queue(txq1->core_txq);
+	smp_mb();
+	txq1->old_read_count = ACCESS_ONCE(txq1->read_count);
+	txq2->old_read_count = ACCESS_ONCE(txq2->read_count);
+
+	fill_level = max(txq1->insert_count - txq1->old_read_count,
+			 txq2->insert_count - txq2->old_read_count);
+	EFX_BUG_ON_PARANOID(fill_level >= efx->txq_entries);
+	if (likely(fill_level < efx->txq_stop_thresh)) {
+		smp_mb();
+		if (likely(!efx->loopback_selftest))
+			netif_tx_start_queue(txq1->core_txq);
+	}
+}
+
+/*
+ * Add a socket buffer to a TX queue
+ *
+ * This maps all fragments of a socket buffer for DMA and adds them to
+ * the TX queue.  The queue's insert pointer will be incremented by
+ * the number of fragments in the socket buffer.
+ *
+ * If any DMA mapping fails, any mapped fragments will be unmapped,
+ * the queue's insert pointer will be restored to its original value.
+ *
+ * This function is split out from efx_hard_start_xmit to allow the
+ * loopback test to direct packets via specific TX queues.
+ *
+ * Returns NETDEV_TX_OK.
+ * You must hold netif_tx_lock() to call this function.
+ */
+netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
+{
+	struct efx_nic *efx = tx_queue->efx;
+	struct device *dma_dev = &efx->pci_dev->dev;
+	struct efx_tx_buffer *buffer;
+	skb_frag_t *fragment;
+	unsigned int len, unmap_len = 0, insert_ptr;
+	dma_addr_t dma_addr, unmap_addr = 0;
+	unsigned int dma_len;
+	unsigned short dma_flags;
+	int i = 0;
+
+	EFX_BUG_ON_PARANOID(tx_queue->write_count != tx_queue->insert_count);
+
+	if (skb_shinfo(skb)->gso_size)
+		return efx_enqueue_skb_tso(tx_queue, skb);
+
+	/* Get size of the initial fragment */
+	len = skb_headlen(skb);
+
+	/* Pad if necessary */
+	if (EFX_WORKAROUND_15592(efx) && skb->len <= 32) {
+		EFX_BUG_ON_PARANOID(skb->data_len);
+		len = 32 + 1;
+		if (skb_pad(skb, len - skb->len))
+			return NETDEV_TX_OK;
+	}
+
+	/* Map for DMA.  Use dma_map_single rather than dma_map_page
+	 * since this is more efficient on machines with sparse
+	 * memory.
+	 */
+	dma_flags = EFX_TX_BUF_MAP_SINGLE;
+	dma_addr = dma_map_single(dma_dev, skb->data, len, PCI_DMA_TODEVICE);
+
+	/* Process all fragments */
+	while (1) {
+		if (unlikely(dma_mapping_error(dma_dev, dma_addr)))
+			goto dma_err;
+
+		/* Store fields for marking in the per-fragment final
+		 * descriptor */
+		unmap_len = len;
+		unmap_addr = dma_addr;
+
+		/* Add to TX queue, splitting across DMA boundaries */
+		do {
+			insert_ptr = tx_queue->insert_count & tx_queue->ptr_mask;
+			buffer = &tx_queue->buffer[insert_ptr];
+			EFX_BUG_ON_PARANOID(buffer->flags);
+			EFX_BUG_ON_PARANOID(buffer->len);
+			EFX_BUG_ON_PARANOID(buffer->unmap_len);
+
+			dma_len = efx_max_tx_len(efx, dma_addr);
+			if (likely(dma_len >= len))
+				dma_len = len;
+
+			/* Fill out per descriptor fields */
+			buffer->len = dma_len;
+			buffer->dma_addr = dma_addr;
+			buffer->flags = EFX_TX_BUF_CONT;
+			len -= dma_len;
+			dma_addr += dma_len;
+			++tx_queue->insert_count;
+		} while (len);
+
+		/* Transfer ownership of the unmapping to the final buffer */
+		buffer->flags = EFX_TX_BUF_CONT | dma_flags;
+		buffer->unmap_len = unmap_len;
+		unmap_len = 0;
+
+		/* Get address and size of next fragment */
+		if (i >= skb_shinfo(skb)->nr_frags)
+			break;
+		fragment = &skb_shinfo(skb)->frags[i];
+		len = skb_frag_size(fragment);
+		i++;
+		/* Map for DMA */
+		dma_flags = 0;
+		dma_addr = skb_frag_dma_map(dma_dev, fragment, 0, len,
+					    DMA_TO_DEVICE);
+	}
+
+	/* Transfer ownership of the skb to the final buffer */
+	buffer->skb = skb;
+	buffer->flags = EFX_TX_BUF_SKB | dma_flags;
+
+	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);
+
+	/* Pass off to hardware */
+	efx_nic_push_buffers(tx_queue);
+
+	efx_tx_maybe_stop_queue(tx_queue);
+
+	return NETDEV_TX_OK;
+
+ dma_err:
+	netif_err(efx, tx_err, efx->net_dev,
+		  " TX queue %d could not map skb with %d bytes %d "
+		  "fragments for DMA\n", tx_queue->queue, skb->len,
+		  skb_shinfo(skb)->nr_frags + 1);
+
+	/* Mark the packet as transmitted, and free the SKB ourselves */
+	dev_kfree_skb_any(skb);
+
+	/* Work backwards until we hit the original insert pointer value */
+	while (tx_queue->insert_count != tx_queue->write_count) {
+		unsigned int pkts_compl = 0, bytes_compl = 0;
+		--tx_queue->insert_count;
+		insert_ptr = tx_queue->insert_count & tx_queue->ptr_mask;
+		buffer = &tx_queue->buffer[insert_ptr];
+		efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
+	}
+
+	/* Free the fragment we were mid-way through pushing */
+	if (unmap_len) {
+		if (dma_flags & EFX_TX_BUF_MAP_SINGLE)
+			dma_unmap_single(dma_dev, unmap_addr, unmap_len,
+					 DMA_TO_DEVICE);
+		else
+			dma_unmap_page(dma_dev, unmap_addr, unmap_len,
+				       DMA_TO_DEVICE);
+	}
+
+	return NETDEV_TX_OK;
+}
+
+/* Remove packets from the TX queue
+ *
+ * This removes packets from the TX queue, up to and including the
+ * specified index.
+ */
+static void efx_dequeue_buffers(struct efx_tx_queue *tx_queue,
+				unsigned int index,
+				unsigned int *pkts_compl,
+				unsigned int *bytes_compl)
+{
+	struct efx_nic *efx = tx_queue->efx;
+	unsigned int stop_index, read_ptr;
+
+	stop_index = (index + 1) & tx_queue->ptr_mask;
+	read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
+
+	while (read_ptr != stop_index) {
+		struct efx_tx_buffer *buffer = &tx_queue->buffer[read_ptr];
+		if (unlikely(buffer->len == 0)) {
+			netif_err(efx, tx_err, efx->net_dev,
+				  "TX queue %d spurious TX completion id %x\n",
+				  tx_queue->queue, read_ptr);
+			efx_schedule_reset(efx, RESET_TYPE_TX_SKIP);
+			return;
+		}
+
+		efx_dequeue_buffer(tx_queue, buffer, pkts_compl, bytes_compl);
+
+		++tx_queue->read_count;
+		read_ptr = tx_queue->read_count & tx_queue->ptr_mask;
+	}
+}
+
+/* Initiate a packet transmission.  We use one channel per CPU
+ * (sharing when we have more CPUs than channels).  On Falcon, the TX
+ * completion events will be directed back to the CPU that transmitted
+ * the packet, which should be cache-efficient.
+ *
+ * Context: non-blocking.
+ * Note that returning anything other than NETDEV_TX_OK will cause the
+ * OS to free the skb.
+ */
+netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
+				struct net_device *net_dev)
+{
+	struct efx_nic *efx = netdev_priv(net_dev);
+	struct efx_tx_queue *tx_queue;
+	unsigned index, type;
+
+	EFX_WARN_ON_PARANOID(!netif_device_present(net_dev));
+
+	/* PTP "event" packet */
+	if (unlikely(efx_xmit_with_hwtstamp(skb)) &&
+	    unlikely(efx_ptp_is_ptp_tx(efx, skb))) {
+		return efx_ptp_tx(efx, skb);
+	}
+
+	index = skb_get_queue_mapping(skb);
+	type = skb->ip_summed == CHECKSUM_PARTIAL ? EFX_TXQ_TYPE_OFFLOAD : 0;
+	if (index >= efx->n_tx_channels) {
+		index -= efx->n_tx_channels;
+		type |= EFX_TXQ_TYPE_HIGHPRI;
+	}
+	tx_queue = efx_get_tx_queue(efx, index, type);
+
+	return efx_enqueue_skb(tx_queue, skb);
+}
+
+void efx_init_tx_queue_core_txq(struct efx_tx_queue *tx_queue)
+{
+	struct efx_nic *efx = tx_queue->efx;
+
+	/* Must be inverse of queue lookup in efx_hard_start_xmit() */
+	tx_queue->core_txq =
+		netdev_get_tx_queue(efx->net_dev,
+				    tx_queue->queue / EFX_TXQ_TYPES +
+				    ((tx_queue->queue & EFX_TXQ_TYPE_HIGHPRI) ?
+				     efx->n_tx_channels : 0));
+}
+
+int efx_setup_tc(struct net_device *net_dev, u8 num_tc)
+{
+	struct efx_nic *efx = netdev_priv(net_dev);
+	struct efx_channel *channel;
+	struct efx_tx_queue *tx_queue;
+	unsigned tc;
+	int rc;
+
+	if (efx_nic_rev(efx) < EFX_REV_FALCON_B0 || num_tc > EFX_MAX_TX_TC)
+		return -EINVAL;
+
+	if (num_tc == net_dev->num_tc)
+		return 0;
+
+	for (tc = 0; tc < num_tc; tc++) {
+		net_dev->tc_to_txq[tc].offset = tc * efx->n_tx_channels;
+		net_dev->tc_to_txq[tc].count = efx->n_tx_channels;
+	}
+
+	if (num_tc > net_dev->num_tc) {
+		/* Initialise high-priority queues as necessary */
+		efx_for_each_channel(channel, efx) {
+			efx_for_each_possible_channel_tx_queue(tx_queue,
+							       channel) {
+				if (!(tx_queue->queue & EFX_TXQ_TYPE_HIGHPRI))
+					continue;
+				if (!tx_queue->buffer) {
+					rc = efx_probe_tx_queue(tx_queue);
+					if (rc)
+						return rc;
+				}
+				if (!tx_queue->initialised)
+					efx_init_tx_queue(tx_queue);
+				efx_init_tx_queue_core_txq(tx_queue);
+			}
+		}
+	} else {
+		/* Reduce number of classes before number of queues */
+		net_dev->num_tc = num_tc;
+	}
+
+	rc = netif_set_real_num_tx_queues(net_dev,
+					  max_t(int, num_tc, 1) *
+					  efx->n_tx_channels);
+	if (rc)
+		return rc;
+
+	/* Do not destroy high-priority queues when they become
+	 * unused.  We would have to flush them first, and it is
+	 * fairly difficult to flush a subset of TX queues.  Leave
+	 * it to efx_fini_channels().
+	 */
+
+	net_dev->num_tc = num_tc;
+	return 0;
+}
+
+void efx_xmit_done(struct efx_tx_queue *tx_queue, unsigned int index)
+{
+	unsigned fill_level;
+	struct efx_nic *efx = tx_queue->efx;
+	struct efx_tx_queue *txq2;
+	unsigned int pkts_compl = 0, bytes_compl = 0;
+
+	EFX_BUG_ON_PARANOID(index > tx_queue->ptr_mask);
+
+	efx_dequeue_buffers(tx_queue, index, &pkts_compl, &bytes_compl);
+	netdev_tx_completed_queue(tx_queue->core_txq, pkts_compl, bytes_compl);
+
+	/* See if we need to restart the netif queue.  This memory
+	 * barrier ensures that we write read_count (inside
+	 * efx_dequeue_buffers()) before reading the queue status.
+	 */
+	smp_mb();
+	if (unlikely(netif_tx_queue_stopped(tx_queue->core_txq)) &&
+	    likely(efx->port_enabled) &&
+	    likely(netif_device_present(efx->net_dev))) {
+		txq2 = efx_tx_queue_partner(tx_queue);
+		fill_level = max(tx_queue->insert_count - tx_queue->read_count,
+				 txq2->insert_count - txq2->read_count);
+		if (fill_level <= efx->txq_wake_thresh)
+			netif_tx_wake_queue(tx_queue->core_txq);
+	}
+
+	/* Check whether the hardware queue is now empty */
+	if ((int)(tx_queue->read_count - tx_queue->old_write_count) >= 0) {
+		tx_queue->old_write_count = ACCESS_ONCE(tx_queue->write_count);
+		if (tx_queue->read_count == tx_queue->old_write_count) {
+			smp_mb();
+			tx_queue->empty_read_count =
+				tx_queue->read_count | EFX_EMPTY_COUNT_VALID;
+		}
+	}
+}
+
+/* Size of page-based TSO header buffers.  Larger blocks must be
+ * allocated from the heap.
+ */
+#define TSOH_STD_SIZE	128
+#define TSOH_PER_PAGE	(PAGE_SIZE / TSOH_STD_SIZE)
+
+/* 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 skb.
+ */
+static unsigned int efx_tsoh_page_count(struct efx_tx_queue *tx_queue)
+{
+	return DIV_ROUND_UP(tx_queue->ptr_mask + 1, 2 * TSOH_PER_PAGE);
+}
+
+int efx_probe_tx_queue(struct efx_tx_queue *tx_queue)
+{
+	struct efx_nic *efx = tx_queue->efx;
+	unsigned int entries;
+	int rc;
+
+	/* Create the smallest power-of-two aligned ring */
+	entries = max(roundup_pow_of_two(efx->txq_entries), EFX_MIN_DMAQ_SIZE);
+	EFX_BUG_ON_PARANOID(entries > EFX_MAX_DMAQ_SIZE);
+	tx_queue->ptr_mask = entries - 1;
+
+	netif_dbg(efx, probe, efx->net_dev,
+		  "creating TX queue %d size %#x mask %#x\n",
+		  tx_queue->queue, efx->txq_entries, tx_queue->ptr_mask);
+
+	/* Allocate software ring */
+	tx_queue->buffer = kcalloc(entries, sizeof(*tx_queue->buffer),
+				   GFP_KERNEL);
+	if (!tx_queue->buffer)
+		return -ENOMEM;
+
+	if (tx_queue->queue & EFX_TXQ_TYPE_OFFLOAD) {
+		tx_queue->tsoh_page =
+			kcalloc(efx_tsoh_page_count(tx_queue),
+				sizeof(tx_queue->tsoh_page[0]), GFP_KERNEL);
+		if (!tx_queue->tsoh_page) {
+			rc = -ENOMEM;
+			goto fail1;
+		}
+	}
+
+	/* Allocate hardware ring */
+	rc = efx_nic_probe_tx(tx_queue);
+	if (rc)
+		goto fail2;
+
+	return 0;
+
+fail2:
+	kfree(tx_queue->tsoh_page);
+	tx_queue->tsoh_page = NULL;
+fail1:
+	kfree(tx_queue->buffer);
+	tx_queue->buffer = NULL;
+	return rc;
+}
+
+void efx_init_tx_queue(struct efx_tx_queue *tx_queue)
+{
+	netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
+		  "initialising TX queue %d\n", tx_queue->queue);
+
+	tx_queue->insert_count = 0;
+	tx_queue->write_count = 0;
+	tx_queue->old_write_count = 0;
+	tx_queue->read_count = 0;
+	tx_queue->old_read_count = 0;
+	tx_queue->empty_read_count = 0 | EFX_EMPTY_COUNT_VALID;
+
+	/* Set up TX descriptor ring */
+	efx_nic_init_tx(tx_queue);
+
+	tx_queue->initialised = true;
+}
+
+void efx_release_tx_buffers(struct efx_tx_queue *tx_queue)
+{
+	struct efx_tx_buffer *buffer;
+
+	if (!tx_queue->buffer)
+		return;
+
+	/* Free any buffers left in the ring */
+	while (tx_queue->read_count != tx_queue->write_count) {
+		unsigned int pkts_compl = 0, bytes_compl = 0;
+		buffer = &tx_queue->buffer[tx_queue->read_count & tx_queue->ptr_mask];
+		efx_dequeue_buffer(tx_queue, buffer, &pkts_compl, &bytes_compl);
+
+		++tx_queue->read_count;
+	}
+	netdev_tx_reset_queue(tx_queue->core_txq);
+}
+
+void efx_fini_tx_queue(struct efx_tx_queue *tx_queue)
+{
+	if (!tx_queue->initialised)
+		return;
+
+	netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
+		  "shutting down TX queue %d\n", tx_queue->queue);
+
+	tx_queue->initialised = false;
+
+	/* Flush TX queue, remove descriptor ring */
+	efx_nic_fini_tx(tx_queue);
+
+	efx_release_tx_buffers(tx_queue);
+}
+
+void efx_remove_tx_queue(struct efx_tx_queue *tx_queue)
+{
+	int i;
+
+	if (!tx_queue->buffer)
+		return;
+
+	netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
+		  "destroying TX queue %d\n", tx_queue->queue);
+	efx_nic_remove_tx(tx_queue);
+
+	if (tx_queue->tsoh_page) {
+		for (i = 0; i < efx_tsoh_page_count(tx_queue); i++)
+			efx_nic_free_buffer(tx_queue->efx,
+					    &tx_queue->tsoh_page[i]);
+		kfree(tx_queue->tsoh_page);
+		tx_queue->tsoh_page = NULL;
+	}
+
+	kfree(tx_queue->buffer);
+	tx_queue->buffer = NULL;
+}
+
+
+/* Efx TCP segmentation acceleration.
+ *
+ * Why?  Because by doing it here in the driver we can go significantly
+ * faster than the GSO.
+ *
+ * Requires TX checksum offload support.
+ */
+
+/* Number of bytes inserted at the start of a TSO header buffer,
+ * similar to NET_IP_ALIGN.
+ */
+#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
+#define TSOH_OFFSET	0
+#else
+#define TSOH_OFFSET	NET_IP_ALIGN
+#endif
+
+#define PTR_DIFF(p1, p2)  ((u8 *)(p1) - (u8 *)(p2))
+
+/**
+ * struct tso_state - TSO state for an SKB
+ * @out_len: Remaining length in current segment
+ * @seqnum: Current sequence number
+ * @ipv4_id: Current IPv4 ID, host endian
+ * @packet_space: Remaining space in current packet
+ * @dma_addr: DMA address of current position
+ * @in_len: Remaining length in current SKB fragment
+ * @unmap_len: Length of SKB fragment
+ * @unmap_addr: DMA address of SKB fragment
+ * @dma_flags: TX buffer flags for DMA mapping - %EFX_TX_BUF_MAP_SINGLE or 0
+ * @protocol: Network protocol (after any VLAN header)
+ * @ip_off: Offset of IP header
+ * @tcp_off: Offset of TCP header
+ * @header_len: Number of bytes of header
+ * @ip_base_len: IPv4 tot_len or IPv6 payload_len, before TCP payload
+ *
+ * The state used during segmentation.  It is put into this data structure
+ * just to make it easy to pass into inline functions.
+ */
+struct tso_state {
+	/* Output position */
+	unsigned out_len;
+	unsigned seqnum;
+	unsigned ipv4_id;
+	unsigned packet_space;
+
+	/* Input position */
+	dma_addr_t dma_addr;
+	unsigned in_len;
+	unsigned unmap_len;
+	dma_addr_t unmap_addr;
+	unsigned short dma_flags;
+
+	__be16 protocol;
+	unsigned int ip_off;
+	unsigned int tcp_off;
+	unsigned header_len;
+	unsigned int ip_base_len;
+};
+
+
+/*
+ * Verify that our various assumptions about sk_buffs and the conditions
+ * under which TSO will be attempted hold true.  Return the protocol number.
+ */
+static __be16 efx_tso_check_protocol(struct sk_buff *skb)
+{
+	__be16 protocol = skb->protocol;
+
+	EFX_BUG_ON_PARANOID(((struct ethhdr *)skb->data)->h_proto !=
+			    protocol);
+	if (protocol == htons(ETH_P_8021Q)) {
+		struct vlan_ethhdr *veh = (struct vlan_ethhdr *)skb->data;
+		protocol = veh->h_vlan_encapsulated_proto;
+	}
+
+	if (protocol == htons(ETH_P_IP)) {
+		EFX_BUG_ON_PARANOID(ip_hdr(skb)->protocol != IPPROTO_TCP);
+	} else {
+		EFX_BUG_ON_PARANOID(protocol != htons(ETH_P_IPV6));
+		EFX_BUG_ON_PARANOID(ipv6_hdr(skb)->nexthdr != NEXTHDR_TCP);
+	}
+	EFX_BUG_ON_PARANOID((PTR_DIFF(tcp_hdr(skb), skb->data)
+			     + (tcp_hdr(skb)->doff << 2u)) >
+			    skb_headlen(skb));
+
+	return protocol;
+}
+
+static u8 *efx_tsoh_get_buffer(struct efx_tx_queue *tx_queue,
+			       struct efx_tx_buffer *buffer, unsigned int len)
+{
+	u8 *result;
+
+	EFX_BUG_ON_PARANOID(buffer->len);
+	EFX_BUG_ON_PARANOID(buffer->flags);
+	EFX_BUG_ON_PARANOID(buffer->unmap_len);
+
+	if (likely(len <= TSOH_STD_SIZE - TSOH_OFFSET)) {
+		unsigned index =
+			(tx_queue->insert_count & tx_queue->ptr_mask) / 2;
+		struct efx_buffer *page_buf =
+			&tx_queue->tsoh_page[index / TSOH_PER_PAGE];
+		unsigned offset =
+			TSOH_STD_SIZE * (index % TSOH_PER_PAGE) + TSOH_OFFSET;
+
+		if (unlikely(!page_buf->addr) &&
+		    efx_nic_alloc_buffer(tx_queue->efx, page_buf, PAGE_SIZE))
+			return NULL;
+
+		result = (u8 *)page_buf->addr + offset;
+		buffer->dma_addr = page_buf->dma_addr + offset;
+		buffer->flags = EFX_TX_BUF_CONT;
+	} else {
+		tx_queue->tso_long_headers++;
+
+		buffer->heap_buf = kmalloc(TSOH_OFFSET + len, GFP_ATOMIC);
+		if (unlikely(!buffer->heap_buf))
+			return NULL;
+		result = (u8 *)buffer->heap_buf + TSOH_OFFSET;
+		buffer->flags = EFX_TX_BUF_CONT | EFX_TX_BUF_HEAP;
+	}
+
+	buffer->len = len;
+
+	return result;
+}
+
+/**
+ * efx_tx_queue_insert - push descriptors onto the TX queue
+ * @tx_queue:		Efx TX queue
+ * @dma_addr:		DMA address of fragment
+ * @len:		Length of fragment
+ * @final_buffer:	The final buffer inserted into the queue
+ *
+ * Push descriptors onto the TX queue.
+ */
+static void efx_tx_queue_insert(struct efx_tx_queue *tx_queue,
+				dma_addr_t dma_addr, unsigned len,
+				struct efx_tx_buffer **final_buffer)
+{
+	struct efx_tx_buffer *buffer;
+	struct efx_nic *efx = tx_queue->efx;
+	unsigned dma_len, insert_ptr;
+
+	EFX_BUG_ON_PARANOID(len <= 0);
+
+	while (1) {
+		insert_ptr = tx_queue->insert_count & tx_queue->ptr_mask;
+		buffer = &tx_queue->buffer[insert_ptr];
+		++tx_queue->insert_count;
+
+		EFX_BUG_ON_PARANOID(tx_queue->insert_count -
+				    tx_queue->read_count >=
+				    efx->txq_entries);
+
+		EFX_BUG_ON_PARANOID(buffer->len);
+		EFX_BUG_ON_PARANOID(buffer->unmap_len);
+		EFX_BUG_ON_PARANOID(buffer->flags);
+
+		buffer->dma_addr = dma_addr;
+
+		dma_len = efx_max_tx_len(efx, dma_addr);
+
+		/* If there is enough space to send then do so */
+		if (dma_len >= len)
+			break;
+
+		buffer->len = dma_len;
+		buffer->flags = EFX_TX_BUF_CONT;
+		dma_addr += dma_len;
+		len -= dma_len;
+	}
+
+	EFX_BUG_ON_PARANOID(!len);
+	buffer->len = len;
+	*final_buffer = buffer;
+}
+
+
+/*
+ * Put a TSO header into the TX queue.
+ *
+ * This is special-cased because we know that it is small enough to fit in
+ * a single fragment, and we know it doesn't cross a page boundary.  It
+ * also allows us to not worry about end-of-packet etc.
+ */
+static int efx_tso_put_header(struct efx_tx_queue *tx_queue,
+			      struct efx_tx_buffer *buffer, u8 *header)
+{
+	if (unlikely(buffer->flags & EFX_TX_BUF_HEAP)) {
+		buffer->dma_addr = dma_map_single(&tx_queue->efx->pci_dev->dev,
+						  header, buffer->len,
+						  DMA_TO_DEVICE);
+		if (unlikely(dma_mapping_error(&tx_queue->efx->pci_dev->dev,
+					       buffer->dma_addr))) {
+			kfree(buffer->heap_buf);
+			buffer->len = 0;
+			buffer->flags = 0;
+			return -ENOMEM;
+		}
+		buffer->unmap_len = buffer->len;
+		buffer->flags |= EFX_TX_BUF_MAP_SINGLE;
+	}
+
+	++tx_queue->insert_count;
+	return 0;
+}
+
+
+/* Remove buffers put into a tx_queue.  None of the buffers must have
+ * an skb attached.
+ */
+static void efx_enqueue_unwind(struct efx_tx_queue *tx_queue)
+{
+	struct efx_tx_buffer *buffer;
+
+	/* Work backwards until we hit the original insert pointer value */
+	while (tx_queue->insert_count != tx_queue->write_count) {
+		--tx_queue->insert_count;
+		buffer = &tx_queue->buffer[tx_queue->insert_count &
+					   tx_queue->ptr_mask];
+		efx_dequeue_buffer(tx_queue, buffer, NULL, NULL);
+	}
+}
+
+
+/* Parse the SKB header and initialise state. */
+static void tso_start(struct tso_state *st, const struct sk_buff *skb)
+{
+	st->ip_off = skb_network_header(skb) - skb->data;
+	st->tcp_off = skb_transport_header(skb) - skb->data;
+	st->header_len = st->tcp_off + (tcp_hdr(skb)->doff << 2u);
+	if (st->protocol == htons(ETH_P_IP)) {
+		st->ip_base_len = st->header_len - st->ip_off;
+		st->ipv4_id = ntohs(ip_hdr(skb)->id);
+	} else {
+		st->ip_base_len = st->header_len - st->tcp_off;
+		st->ipv4_id = 0;
+	}
+	st->seqnum = ntohl(tcp_hdr(skb)->seq);
+
+	EFX_BUG_ON_PARANOID(tcp_hdr(skb)->urg);
+	EFX_BUG_ON_PARANOID(tcp_hdr(skb)->syn);
+	EFX_BUG_ON_PARANOID(tcp_hdr(skb)->rst);
+
+	st->out_len = skb->len - st->header_len;
+	st->unmap_len = 0;
+	st->dma_flags = 0;
+}
+
+static int tso_get_fragment(struct tso_state *st, struct efx_nic *efx,
+			    skb_frag_t *frag)
+{
+	st->unmap_addr = skb_frag_dma_map(&efx->pci_dev->dev, frag, 0,
+					  skb_frag_size(frag), DMA_TO_DEVICE);
+	if (likely(!dma_mapping_error(&efx->pci_dev->dev, st->unmap_addr))) {
+		st->dma_flags = 0;
+		st->unmap_len = skb_frag_size(frag);
+		st->in_len = skb_frag_size(frag);
+		st->dma_addr = st->unmap_addr;
+		return 0;
+	}
+	return -ENOMEM;
+}
+
+static int tso_get_head_fragment(struct tso_state *st, struct efx_nic *efx,
+				 const struct sk_buff *skb)
+{
+	int hl = st->header_len;
+	int len = skb_headlen(skb) - hl;
+
+	st->unmap_addr = dma_map_single(&efx->pci_dev->dev, skb->data + hl,
+					len, DMA_TO_DEVICE);
+	if (likely(!dma_mapping_error(&efx->pci_dev->dev, st->unmap_addr))) {
+		st->dma_flags = EFX_TX_BUF_MAP_SINGLE;
+		st->unmap_len = len;
+		st->in_len = len;
+		st->dma_addr = st->unmap_addr;
+		return 0;
+	}
+	return -ENOMEM;
+}
+
+
+/**
+ * tso_fill_packet_with_fragment - form descriptors for the current fragment
+ * @tx_queue:		Efx TX queue
+ * @skb:		Socket buffer
+ * @st:			TSO state
+ *
+ * Form descriptors for the current fragment, until we reach the end
+ * of fragment or end-of-packet.
+ */
+static void tso_fill_packet_with_fragment(struct efx_tx_queue *tx_queue,
+					  const struct sk_buff *skb,
+					  struct tso_state *st)
+{
+	struct efx_tx_buffer *buffer;
+	int n;
+
+	if (st->in_len == 0)
+		return;
+	if (st->packet_space == 0)
+		return;
+
+	EFX_BUG_ON_PARANOID(st->in_len <= 0);
+	EFX_BUG_ON_PARANOID(st->packet_space <= 0);
+
+	n = min(st->in_len, st->packet_space);
+
+	st->packet_space -= n;
+	st->out_len -= n;
+	st->in_len -= n;
+
+	efx_tx_queue_insert(tx_queue, st->dma_addr, n, &buffer);
+
+	if (st->out_len == 0) {
+		/* Transfer ownership of the skb */
+		buffer->skb = skb;
+		buffer->flags = EFX_TX_BUF_SKB;
+	} else if (st->packet_space != 0) {
+		buffer->flags = EFX_TX_BUF_CONT;
+	}
+
+	if (st->in_len == 0) {
+		/* Transfer ownership of the DMA mapping */
+		buffer->unmap_len = st->unmap_len;
+		buffer->flags |= st->dma_flags;
+		st->unmap_len = 0;
+	}
+
+	st->dma_addr += n;
+}
+
+
+/**
+ * tso_start_new_packet - generate a new header and prepare for the new packet
+ * @tx_queue:		Efx TX queue
+ * @skb:		Socket buffer
+ * @st:			TSO state
+ *
+ * Generate a new header and prepare for the new packet.  Return 0 on
+ * success, or -%ENOMEM if failed to alloc header.
+ */
+static int tso_start_new_packet(struct efx_tx_queue *tx_queue,
+				const struct sk_buff *skb,
+				struct tso_state *st)
+{
+	struct efx_tx_buffer *buffer =
+		&tx_queue->buffer[tx_queue->insert_count & tx_queue->ptr_mask];
+	struct tcphdr *tsoh_th;
+	unsigned ip_length;
+	u8 *header;
+	int rc;
+
+	/* Allocate and insert a DMA-mapped header buffer. */
+	header = efx_tsoh_get_buffer(tx_queue, buffer, st->header_len);
+	if (!header)
+		return -ENOMEM;
+
+	tsoh_th = (struct tcphdr *)(header + st->tcp_off);
+
+	/* Copy and update the headers. */
+	memcpy(header, skb->data, st->header_len);
+
+	tsoh_th->seq = htonl(st->seqnum);
+	st->seqnum += skb_shinfo(skb)->gso_size;
+	if (st->out_len > skb_shinfo(skb)->gso_size) {
+		/* This packet will not finish the TSO burst. */
+		st->packet_space = skb_shinfo(skb)->gso_size;
+		tsoh_th->fin = 0;
+		tsoh_th->psh = 0;
+	} else {
+		/* This packet will be the last in the TSO burst. */
+		st->packet_space = st->out_len;
+		tsoh_th->fin = tcp_hdr(skb)->fin;
+		tsoh_th->psh = tcp_hdr(skb)->psh;
+	}
+	ip_length = st->ip_base_len + st->packet_space;
+
+	if (st->protocol == htons(ETH_P_IP)) {
+		struct iphdr *tsoh_iph = (struct iphdr *)(header + st->ip_off);
+
+		tsoh_iph->tot_len = htons(ip_length);
+
+		/* Linux leaves suitable gaps in the IP ID space for us to fill. */
+		tsoh_iph->id = htons(st->ipv4_id);
+		st->ipv4_id++;
+	} else {
+		struct ipv6hdr *tsoh_iph =
+			(struct ipv6hdr *)(header + st->ip_off);
+
+		tsoh_iph->payload_len = htons(ip_length);
+	}
+
+	rc = efx_tso_put_header(tx_queue, buffer, header);
+	if (unlikely(rc))
+		return rc;
+
+	++tx_queue->tso_packets;
+
+	return 0;
+}
+
+
+/**
+ * efx_enqueue_skb_tso - segment and transmit a TSO socket buffer
+ * @tx_queue:		Efx TX queue
+ * @skb:		Socket buffer
+ *
+ * Context: You must hold netif_tx_lock() to call this function.
+ *
+ * Add socket buffer @skb to @tx_queue, doing TSO or return != 0 if
+ * @skb was not enqueued.  In all cases @skb is consumed.  Return
+ * %NETDEV_TX_OK.
+ */
+static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue,
+			       struct sk_buff *skb)
+{
+	struct efx_nic *efx = tx_queue->efx;
+	int frag_i, rc;
+	struct tso_state state;
+
+	/* Find the packet protocol and sanity-check it */
+	state.protocol = efx_tso_check_protocol(skb);
+
+	EFX_BUG_ON_PARANOID(tx_queue->write_count != tx_queue->insert_count);
+
+	tso_start(&state, skb);
+
+	/* Assume that skb header area contains exactly the headers, and
+	 * all payload is in the frag list.
+	 */
+	if (skb_headlen(skb) == state.header_len) {
+		/* Grab the first payload fragment. */
+		EFX_BUG_ON_PARANOID(skb_shinfo(skb)->nr_frags < 1);
+		frag_i = 0;
+		rc = tso_get_fragment(&state, efx,
+				      skb_shinfo(skb)->frags + frag_i);
+		if (rc)
+			goto mem_err;
+	} else {
+		rc = tso_get_head_fragment(&state, efx, skb);
+		if (rc)
+			goto mem_err;
+		frag_i = -1;
+	}
+
+	if (tso_start_new_packet(tx_queue, skb, &state) < 0)
+		goto mem_err;
+
+	while (1) {
+		tso_fill_packet_with_fragment(tx_queue, skb, &state);
+
+		/* Move onto the next fragment? */
+		if (state.in_len == 0) {
+			if (++frag_i >= skb_shinfo(skb)->nr_frags)
+				/* End of payload reached. */
+				break;
+			rc = tso_get_fragment(&state, efx,
+					      skb_shinfo(skb)->frags + frag_i);
+			if (rc)
+				goto mem_err;
+		}
+
+		/* Start at new packet? */
+		if (state.packet_space == 0 &&
+		    tso_start_new_packet(tx_queue, skb, &state) < 0)
+			goto mem_err;
+	}
+
+	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);
+
+	/* Pass off to hardware */
+	efx_nic_push_buffers(tx_queue);
+
+	efx_tx_maybe_stop_queue(tx_queue);
+
+	tx_queue->tso_bursts++;
+	return NETDEV_TX_OK;
+
+ mem_err:
+	netif_err(efx, tx_err, efx->net_dev,
+		  "Out of memory for TSO headers, or DMA mapping error\n");
+	dev_kfree_skb_any(skb);
+
+	/* Free the DMA mapping we were in the process of writing out */
+	if (state.unmap_len) {
+		if (state.dma_flags & EFX_TX_BUF_MAP_SINGLE)
+			dma_unmap_single(&efx->pci_dev->dev, state.unmap_addr,
+					 state.unmap_len, DMA_TO_DEVICE);
+		else
+			dma_unmap_page(&efx->pci_dev->dev, state.unmap_addr,
+				       state.unmap_len, DMA_TO_DEVICE);
+	}
+
+	efx_enqueue_unwind(tx_queue);
+	return NETDEV_TX_OK;
+}