sfc: Firmware-Assisted TSO version 2

Add support for FATSOv2 to the driver. FATSOv2 offloads far more of the task
 of TCP segmentation to the firmware, such that we now just pass a single
 super-packet to the NIC. This means TSO has a great deal in common with a
 normal DMA transmit, apart from adding a couple of option descriptors.
 NIC-specific checks have been moved off the fast path and in to
 initialisation where possible.

This also moves FATSOv1/SWTSO to a new file (tx_tso.c).  The end of transmit
 and some error handling is now outside TSO, since it is common with other
 code.

Signed-off-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sfc/Makefile

@@ -1,7 +1,7 @@
 sfc-y			+= efx.o nic.o farch.o falcon.o siena.o ef10.o tx.o \
 			   rx.o selftest.o ethtool.o qt202x_phy.o mdio_10g.o \
 			   tenxpress.o txc43128_phy.o falcon_boards.o \
-			   mcdi.o mcdi_port.o mcdi_mon.o ptp.o
+			   mcdi.o mcdi_port.o mcdi_mon.o ptp.o tx_tso.o
 sfc-$(CONFIG_SFC_MTD)	+= mtd.o
 sfc-$(CONFIG_SFC_SRIOV)	+= sriov.o siena_sriov.o ef10_sriov.o
 

drivers/net/ethernet/sfc/ef10.c

@@ -2086,6 +2086,78 @@ static inline void efx_ef10_push_tx_desc(struct efx_tx_queue *tx_queue,
 			ER_DZ_TX_DESC_UPD, tx_queue->queue);
 }
 
+/* Add Firmware-Assisted TSO v2 option descriptors to a queue.
+ */
+static int efx_ef10_tx_tso_desc(struct efx_tx_queue *tx_queue,
+				struct sk_buff *skb,
+				bool *data_mapped)
+{
+	struct efx_tx_buffer *buffer;
+	struct tcphdr *tcp;
+	struct iphdr *ip;
+
+	u16 ipv4_id;
+	u32 seqnum;
+	u32 mss;
+
+	EFX_BUG_ON_PARANOID(tx_queue->tso_version != 2);
+
+	mss = skb_shinfo(skb)->gso_size;
+
+	if (unlikely(mss < 4)) {
+		WARN_ONCE(1, "MSS of %u is too small for TSO v2\n", mss);
+		return -EINVAL;
+	}
+
+	ip = ip_hdr(skb);
+	if (ip->version == 4) {
+		/* Modify IPv4 header if needed. */
+		ip->tot_len = 0;
+		ip->check = 0;
+		ipv4_id = ip->id;
+	} else {
+		/* Modify IPv6 header if needed. */
+		struct ipv6hdr *ipv6 = ipv6_hdr(skb);
+
+		ipv6->payload_len = 0;
+		ipv4_id = 0;
+	}
+
+	tcp = tcp_hdr(skb);
+	seqnum = ntohl(tcp->seq);
+
+	buffer = efx_tx_queue_get_insert_buffer(tx_queue);
+
+	buffer->flags = EFX_TX_BUF_OPTION;
+	buffer->len = 0;
+	buffer->unmap_len = 0;
+	EFX_POPULATE_QWORD_5(buffer->option,
+			ESF_DZ_TX_DESC_IS_OPT, 1,
+			ESF_DZ_TX_OPTION_TYPE, ESE_DZ_TX_OPTION_DESC_TSO,
+			ESF_DZ_TX_TSO_OPTION_TYPE,
+			ESE_DZ_TX_TSO_OPTION_DESC_FATSO2A,
+			ESF_DZ_TX_TSO_IP_ID, ipv4_id,
+			ESF_DZ_TX_TSO_TCP_SEQNO, seqnum
+			);
+	++tx_queue->insert_count;
+
+	buffer = efx_tx_queue_get_insert_buffer(tx_queue);
+
+	buffer->flags = EFX_TX_BUF_OPTION;
+	buffer->len = 0;
+	buffer->unmap_len = 0;
+	EFX_POPULATE_QWORD_4(buffer->option,
+			ESF_DZ_TX_DESC_IS_OPT, 1,
+			ESF_DZ_TX_OPTION_TYPE, ESE_DZ_TX_OPTION_DESC_TSO,
+			ESF_DZ_TX_TSO_OPTION_TYPE,
+			ESE_DZ_TX_TSO_OPTION_DESC_FATSO2B,
+			ESF_DZ_TX_TSO_TCP_MSS, mss
+			);
+	++tx_queue->insert_count;
+
+	return 0;
+}
+
 static void efx_ef10_tx_init(struct efx_tx_queue *tx_queue)
 {
 	MCDI_DECLARE_BUF(inbuf, MC_CMD_INIT_TXQ_IN_LEN(EFX_MAX_DMAQ_SIZE * 8 /
@@ -2095,6 +2167,7 @@ static void efx_ef10_tx_init(struct efx_tx_queue *tx_queue)
 	struct efx_channel *channel = tx_queue->channel;
 	struct efx_nic *efx = tx_queue->efx;
 	struct efx_ef10_nic_data *nic_data = efx->nic_data;
+	bool tso_v2 = false;
 	size_t inlen;
 	dma_addr_t dma_addr;
 	efx_qword_t *txd;
@@ -2102,13 +2175,33 @@ static void efx_ef10_tx_init(struct efx_tx_queue *tx_queue)
 	int i;
 	BUILD_BUG_ON(MC_CMD_INIT_TXQ_OUT_LEN != 0);
 
+	/* TSOv2 is a limited resource that can only be configured on a limited
+	 * number of queues. TSO without checksum offload is not really a thing,
+	 * so we only enable it for those queues.
+	 *
+	 * TODO: handle failure to allocate this in the case where we've used
+	 * all the queues.
+	 */
+	if (csum_offload && (nic_data->datapath_caps2 &
+			(1 << MC_CMD_GET_CAPABILITIES_V2_OUT_TX_TSO_V2_LBN))) {
+		tso_v2 = true;
+		netif_dbg(efx, hw, efx->net_dev, "Using TSOv2 for channel %u\n",
+				channel->channel);
+	}
+
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_SIZE, tx_queue->ptr_mask + 1);
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_TARGET_EVQ, channel->channel);
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_LABEL, tx_queue->queue);
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_INSTANCE, tx_queue->queue);
-	MCDI_POPULATE_DWORD_2(inbuf, INIT_TXQ_IN_FLAGS,
+	MCDI_POPULATE_DWORD_3(inbuf, INIT_TXQ_IN_FLAGS,
+			      /* This flag was removed from mcdi_pcol.h for
+			       * the non-_EXT version of INIT_TXQ.  However,
+			       * firmware still honours it.
+			       */
+			      INIT_TXQ_EXT_IN_FLAG_TSOV2_EN, tso_v2,
 			      INIT_TXQ_IN_FLAG_IP_CSUM_DIS, !csum_offload,
 			      INIT_TXQ_IN_FLAG_TCP_CSUM_DIS, !csum_offload);
+
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_OWNER_ID, 0);
 	MCDI_SET_DWORD(inbuf, INIT_TXQ_IN_PORT_ID, nic_data->vport_id);
 
@@ -2146,8 +2239,11 @@ static void efx_ef10_tx_init(struct efx_tx_queue *tx_queue)
 			     ESF_DZ_TX_OPTION_IP_CSUM, csum_offload);
 	tx_queue->write_count = 1;
 
-	if (nic_data->datapath_caps &
-	    (1 << MC_CMD_GET_CAPABILITIES_OUT_TX_TSO_LBN)) {
+	if (tso_v2) {
+		tx_queue->handle_tso = efx_ef10_tx_tso_desc;
+		tx_queue->tso_version = 2;
+	} else if (nic_data->datapath_caps &
+			(1 << MC_CMD_GET_CAPABILITIES_OUT_TX_TSO_LBN)) {
 		tx_queue->tso_version = 1;
 	}
 
@@ -2202,6 +2298,25 @@ static inline void efx_ef10_notify_tx_desc(struct efx_tx_queue *tx_queue)
 			ER_DZ_TX_DESC_UPD_DWORD, tx_queue->queue);
 }
 
+#define EFX_EF10_MAX_TX_DESCRIPTOR_LEN 0x3fff
+
+static unsigned int efx_ef10_tx_limit_len(struct efx_tx_queue *tx_queue,
+					  dma_addr_t dma_addr, unsigned int len)
+{
+	if (len > EFX_EF10_MAX_TX_DESCRIPTOR_LEN) {
+		/* If we need to break across multiple descriptors we should
+		 * stop at a page boundary. This assumes the length limit is
+		 * greater than the page size.
+		 */
+		dma_addr_t end = dma_addr + EFX_EF10_MAX_TX_DESCRIPTOR_LEN;
+
+		BUILD_BUG_ON(EFX_EF10_MAX_TX_DESCRIPTOR_LEN < EFX_PAGE_SIZE);
+		len = (end & (~(EFX_PAGE_SIZE - 1))) - dma_addr;
+	}
+
+	return len;
+}
+
 static void efx_ef10_tx_write(struct efx_tx_queue *tx_queue)
 {
 	unsigned int old_write_count = tx_queue->write_count;
@@ -5469,6 +5584,7 @@ const struct efx_nic_type efx_hunt_a0_vf_nic_type = {
 	.tx_init = efx_ef10_tx_init,
 	.tx_remove = efx_ef10_tx_remove,
 	.tx_write = efx_ef10_tx_write,
+	.tx_limit_len = efx_ef10_tx_limit_len,
 	.rx_push_rss_config = efx_ef10_vf_rx_push_rss_config,
 	.rx_probe = efx_ef10_rx_probe,
 	.rx_init = efx_ef10_rx_init,
@@ -5575,6 +5691,7 @@ const struct efx_nic_type efx_hunt_a0_nic_type = {
 	.tx_init = efx_ef10_tx_init,
 	.tx_remove = efx_ef10_tx_remove,
 	.tx_write = efx_ef10_tx_write,
+	.tx_limit_len = efx_ef10_tx_limit_len,
 	.rx_push_rss_config = efx_ef10_pf_rx_push_rss_config,
 	.rx_probe = efx_ef10_rx_probe,
 	.rx_init = efx_ef10_rx_init,

drivers/net/ethernet/sfc/ethtool.c

@@ -71,6 +71,7 @@ static const struct efx_sw_stat_desc efx_sw_stat_desc[] = {
 	EFX_ETHTOOL_UINT_TXQ_STAT(tso_packets),
 	EFX_ETHTOOL_UINT_TXQ_STAT(pushes),
 	EFX_ETHTOOL_UINT_TXQ_STAT(pio_packets),
+	EFX_ETHTOOL_UINT_TXQ_STAT(cb_packets),
 	EFX_ETHTOOL_ATOMIC_NIC_ERROR_STAT(rx_reset),
 	EFX_ETHTOOL_UINT_CHANNEL_STAT(rx_tobe_disc),
 	EFX_ETHTOOL_UINT_CHANNEL_STAT(rx_ip_hdr_chksum_err),

drivers/net/ethernet/sfc/falcon.c

@@ -2750,6 +2750,7 @@ const struct efx_nic_type falcon_a1_nic_type = {
 	.tx_init = efx_farch_tx_init,
 	.tx_remove = efx_farch_tx_remove,
 	.tx_write = efx_farch_tx_write,
+	.tx_limit_len = efx_farch_tx_limit_len,
 	.rx_push_rss_config = dummy_rx_push_rss_config,
 	.rx_probe = efx_farch_rx_probe,
 	.rx_init = efx_farch_rx_init,
@@ -2849,6 +2850,7 @@ const struct efx_nic_type falcon_b0_nic_type = {
 	.tx_init = efx_farch_tx_init,
 	.tx_remove = efx_farch_tx_remove,
 	.tx_write = efx_farch_tx_write,
+	.tx_limit_len = efx_farch_tx_limit_len,
 	.rx_push_rss_config = falcon_b0_rx_push_rss_config,
 	.rx_probe = efx_farch_rx_probe,
 	.rx_init = efx_farch_rx_init,

drivers/net/ethernet/sfc/farch.c

@@ -356,6 +356,21 @@ void efx_farch_tx_write(struct efx_tx_queue *tx_queue)
 	}
 }
 
+unsigned int efx_farch_tx_limit_len(struct efx_tx_queue *tx_queue,
+				    dma_addr_t dma_addr, unsigned int len)
+{
+	/* Don't cross 4K boundaries with descriptors. */
+	unsigned int limit = (~dma_addr & (EFX_PAGE_SIZE - 1)) + 1;
+
+	len = min(limit, len);
+
+	if (EFX_WORKAROUND_5391(tx_queue->efx) && (dma_addr & 0xf))
+		len = min_t(unsigned int, len, 512 - (dma_addr & 0xf));
+
+	return len;
+}
+
+
 /* Allocate hardware resources for a TX queue */
 int efx_farch_tx_probe(struct efx_tx_queue *tx_queue)
 {

drivers/net/ethernet/sfc/net_driver.h

@@ -189,13 +189,17 @@ struct efx_tx_buffer {
  * @channel: The associated channel
  * @core_txq: The networking core TX queue structure
  * @buffer: The software buffer ring
- * @tsoh_page: Array of pages of TSO header buffers
+ * @cb_page: Array of pages of copy buffers.  Carved up according to
+ *	%EFX_TX_CB_ORDER into %EFX_TX_CB_SIZE-sized chunks.
  * @txd: The hardware descriptor ring
  * @ptr_mask: The size of the ring minus 1.
  * @piobuf: PIO buffer region for this TX queue (shared with its partner).
  *	Size of the region is efx_piobuf_size.
  * @piobuf_offset: Buffer offset to be specified in PIO descriptors
  * @initialised: Has hardware queue been initialised?
+ * @tx_min_size: Minimum transmit size for this queue. Depends on HW.
+ * @handle_tso: TSO xmit preparation handler.  Sets up the TSO metadata and
+ *	may also map tx data, depending on the nature of the TSO implementation.
  * @read_count: Current read pointer.
  *	This is the number of buffers that have been removed from both rings.
  * @old_write_count: The value of @write_count when last checked.
@@ -224,6 +228,7 @@ struct efx_tx_buffer {
  * @pushes: Number of times the TX push feature has been used
  * @pio_packets: Number of times the TX PIO feature has been used
  * @xmit_more_available: Are any packets waiting to be pushed to the NIC
+ * @cb_packets: Number of times the TX copybreak feature has been used
  * @empty_read_count: If the completion path has seen the queue as empty
  *	and the transmission path has not yet checked this, the value of
  *	@read_count bitwise-added to %EFX_EMPTY_COUNT_VALID; otherwise 0.
@@ -236,12 +241,16 @@ struct efx_tx_queue {
 	struct efx_channel *channel;
 	struct netdev_queue *core_txq;
 	struct efx_tx_buffer *buffer;
-	struct efx_buffer *tsoh_page;
+	struct efx_buffer *cb_page;
 	struct efx_special_buffer txd;
 	unsigned int ptr_mask;
 	void __iomem *piobuf;
 	unsigned int piobuf_offset;
 	bool initialised;
+	unsigned int tx_min_size;
+
+	/* Function pointers used in the fast path. */
+	int (*handle_tso)(struct efx_tx_queue*, struct sk_buff*, bool *);
 
 	/* Members used mainly on the completion path */
 	unsigned int read_count ____cacheline_aligned_in_smp;
@@ -260,6 +269,7 @@ struct efx_tx_queue {
 	unsigned int pushes;
 	unsigned int pio_packets;
 	bool xmit_more_available;
+	unsigned int cb_packets;
 	/* Statistics to supplement MAC stats */
 	unsigned long tx_packets;
 
@@ -269,6 +279,9 @@ struct efx_tx_queue {
 	atomic_t flush_outstanding;
 };
 
+#define EFX_TX_CB_ORDER	7
+#define EFX_TX_CB_SIZE	(1 << EFX_TX_CB_ORDER) - NET_IP_ALIGN
+
 /**
  * struct efx_rx_buffer - An Efx RX data buffer
  * @dma_addr: DMA base address of the buffer
@@ -1288,6 +1301,8 @@ struct efx_nic_type {
 	void (*tx_init)(struct efx_tx_queue *tx_queue);
 	void (*tx_remove)(struct efx_tx_queue *tx_queue);
 	void (*tx_write)(struct efx_tx_queue *tx_queue);
+	unsigned int (*tx_limit_len)(struct efx_tx_queue *tx_queue,
+				     dma_addr_t dma_addr, unsigned int len);
 	int (*rx_push_rss_config)(struct efx_nic *efx, bool user,
 				  const u32 *rx_indir_table);
 	int (*rx_probe)(struct efx_rx_queue *rx_queue);
@@ -1545,4 +1560,32 @@ static inline netdev_features_t efx_supported_features(const struct efx_nic *efx
 	return net_dev->features | net_dev->hw_features;
 }
 
+/* Get the current TX queue insert index. */
+static inline unsigned int
+efx_tx_queue_get_insert_index(const struct efx_tx_queue *tx_queue)
+{
+	return tx_queue->insert_count & tx_queue->ptr_mask;
+}
+
+/* Get a TX buffer. */
+static inline struct efx_tx_buffer *
+__efx_tx_queue_get_insert_buffer(const struct efx_tx_queue *tx_queue)
+{
+	return &tx_queue->buffer[efx_tx_queue_get_insert_index(tx_queue)];
+}
+
+/* Get a TX buffer, checking it's not currently in use. */
+static inline struct efx_tx_buffer *
+efx_tx_queue_get_insert_buffer(const struct efx_tx_queue *tx_queue)
+{
+	struct efx_tx_buffer *buffer =
+		__efx_tx_queue_get_insert_buffer(tx_queue);
+
+	EFX_BUG_ON_PARANOID(buffer->len);
+	EFX_BUG_ON_PARANOID(buffer->flags);
+	EFX_BUG_ON_PARANOID(buffer->unmap_len);
+
+	return buffer;
+}
+
 #endif /* EFX_NET_DRIVER_H */

drivers/net/ethernet/sfc/nic.h

@@ -681,6 +681,8 @@ void efx_farch_tx_init(struct efx_tx_queue *tx_queue);
 void efx_farch_tx_fini(struct efx_tx_queue *tx_queue);
 void efx_farch_tx_remove(struct efx_tx_queue *tx_queue);
 void efx_farch_tx_write(struct efx_tx_queue *tx_queue);
+unsigned int efx_farch_tx_limit_len(struct efx_tx_queue *tx_queue,
+				    dma_addr_t dma_addr, unsigned int len);
 int efx_farch_rx_probe(struct efx_rx_queue *rx_queue);
 void efx_farch_rx_init(struct efx_rx_queue *rx_queue);
 void efx_farch_rx_fini(struct efx_rx_queue *rx_queue);

drivers/net/ethernet/sfc/siena.c

@@ -977,6 +977,7 @@ const struct efx_nic_type siena_a0_nic_type = {
 	.tx_init = efx_farch_tx_init,
 	.tx_remove = efx_farch_tx_remove,
 	.tx_write = efx_farch_tx_write,
+	.tx_limit_len = efx_farch_tx_limit_len,
 	.rx_push_rss_config = siena_rx_push_rss_config,
 	.rx_probe = efx_farch_rx_probe,
 	.rx_init = efx_farch_rx_init,

drivers/net/ethernet/sfc/tx.h

@@ -0,0 +1,27 @@
+/****************************************************************************
+ * Driver for Solarflare network controllers and boards
+ * Copyright 2005-2006 Fen Systems Ltd.
+ * Copyright 2006-2015 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.
+ */
+
+#ifndef EFX_TX_H
+#define EFX_TX_H
+
+#include <linux/types.h>
+
+/* Driver internal tx-path related declarations. */
+
+unsigned int efx_tx_limit_len(struct efx_tx_queue *tx_queue,
+			      dma_addr_t dma_addr, unsigned int len);
+
+u8 *efx_tx_get_copy_buffer_limited(struct efx_tx_queue *tx_queue,
+				   struct efx_tx_buffer *buffer, size_t len);
+
+int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, struct sk_buff *skb,
+			bool *data_mapped);
+
+#endif /* EFX_TX_H */