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Commit 70b33fb0 authored by Edward Cree's avatar Edward Cree Committed by David S. Miller
Browse files

sfc: add support for skb->xmit_more 



Don't ring the doorbell, and don't do PIO.  This will also prevent
 TX Push, because there will be more than one buffer waiting when
 the doorbell is rung.

Signed-off-by: default avatarEdward Cree <ecree@solarflare.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6cc69f2a

drivers/net/ethernet/sfc/nic.h

+24 −5
Original line number Diff line number Diff line
@@ -71,9 +71,17 @@ efx_tx_desc(struct efx_tx_queue *tx_queue, unsigned int index) 
	return ((efx_qword_t *) (tx_queue->txd.buf.addr)) + index;

}



/* Report whether the NIC considers this TX queue empty, given the

 * write_count used for the last doorbell push.  May return false

 * negative.

/* 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;

}



/* Report whether this TX queue would be empty for the given write_count.

 * May return false negative.

 */

static inline bool __efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue,

					 unsigned int write_count)
@@ -86,9 +94,18 @@ static inline bool __efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue, 
	return ((empty_read_count ^ write_count) & ~EFX_EMPTY_COUNT_VALID) == 0;

}



static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue)

/* Decide whether we can use TX PIO, ie. write packet data directly into

 * a buffer on the device.  This can reduce latency at the expense of

 * throughput, so we only do this if both hardware and software TX rings

 * are empty.  This also ensures that only one packet at a time can be

 * using the PIO buffer.

 */

static inline bool efx_nic_may_tx_pio(struct efx_tx_queue *tx_queue)

{

	return __efx_nic_tx_is_empty(tx_queue, tx_queue->write_count);

	struct efx_tx_queue *partner = efx_tx_queue_partner(tx_queue);

	return tx_queue->piobuf &&

	       __efx_nic_tx_is_empty(tx_queue, tx_queue->insert_count) &&

	       __efx_nic_tx_is_empty(partner, partner->insert_count);

}



/* Decide whether to push a TX descriptor to the NIC vs merely writing
@@ -96,6 +113,8 @@ static inline bool efx_nic_tx_is_empty(struct efx_tx_queue *tx_queue) 
 * descriptor to an empty queue, but is otherwise pointless.  Further,

 * Falcon and Siena have hardware bugs (SF bug 33851) that may be

 * triggered if we don't check this.

 * We use the write_count used for the last doorbell push, to get the

 * NIC's view of the tx queue.

 */

static inline bool efx_nic_may_push_tx_desc(struct efx_tx_queue *tx_queue,

					    unsigned int write_count)

drivers/net/ethernet/sfc/tx.c

+19 −24
Original line number Diff line number Diff line
@@ -132,15 +132,6 @@ unsigned int efx_tx_max_skb_descs(struct efx_nic *efx) 
	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 */
@@ -344,6 +335,7 @@ 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;

	unsigned int old_insert_count = tx_queue->insert_count;

	skb_frag_t *fragment;

	unsigned int len, unmap_len = 0;

	dma_addr_t dma_addr, unmap_addr = 0;
@@ -351,7 +343,7 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb) 
	unsigned short dma_flags;

	int i = 0;



	EFX_BUG_ON_PARANOID(tx_queue->write_count != tx_queue->insert_count);

	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);
@@ -369,9 +361,8 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb) 


	/* Consider using PIO for short packets */

#ifdef EFX_USE_PIO

	if (skb->len <= efx_piobuf_size && tx_queue->piobuf &&

	    efx_nic_tx_is_empty(tx_queue) &&

	    efx_nic_tx_is_empty(efx_tx_queue_partner(tx_queue))) {

	if (skb->len <= efx_piobuf_size && !skb->xmit_more &&

	    efx_nic_may_tx_pio(tx_queue)) {

		buffer = efx_enqueue_skb_pio(tx_queue, skb);

		dma_flags = EFX_TX_BUF_OPTION;

		goto finish_packet;
@@ -439,13 +430,14 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb) 


	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);



	efx_tx_maybe_stop_queue(tx_queue);



	/* Pass off to hardware */

	if (!skb->xmit_more || netif_xmit_stopped(tx_queue->core_txq))

		efx_nic_push_buffers(tx_queue);



	tx_queue->tx_packets++;



	efx_tx_maybe_stop_queue(tx_queue);



	return NETDEV_TX_OK;



 dma_err:
@@ -458,7 +450,7 @@ netdev_tx_t efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb) 
	dev_kfree_skb_any(skb);



	/* Work backwards until we hit the original insert pointer value */

	while (tx_queue->insert_count != tx_queue->write_count) {

	while (tx_queue->insert_count != old_insert_count) {

		unsigned int pkts_compl = 0, bytes_compl = 0;

		--tx_queue->insert_count;

		buffer = __efx_tx_queue_get_insert_buffer(tx_queue);
@@ -989,12 +981,13 @@ static int efx_tso_put_header(struct efx_tx_queue *tx_queue, 
/* 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)

static void efx_enqueue_unwind(struct efx_tx_queue *tx_queue,

			       unsigned int insert_count)

{

	struct efx_tx_buffer *buffer;



	/* Work backwards until we hit the original insert pointer value */

	while (tx_queue->insert_count != tx_queue->write_count) {

	while (tx_queue->insert_count != insert_count) {

		--tx_queue->insert_count;

		buffer = __efx_tx_queue_get_insert_buffer(tx_queue);

		efx_dequeue_buffer(tx_queue, buffer, NULL, NULL);
@@ -1258,13 +1251,14 @@ static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, 
			       struct sk_buff *skb)

{

	struct efx_nic *efx = tx_queue->efx;

	unsigned int old_insert_count = tx_queue->insert_count;

	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);

	EFX_BUG_ON_PARANOID(tx_queue->write_count > tx_queue->insert_count);



	rc = tso_start(&state, efx, skb);

	if (rc)
@@ -1308,11 +1302,12 @@ static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, 


	netdev_tx_sent_queue(tx_queue->core_txq, skb->len);



	efx_tx_maybe_stop_queue(tx_queue);



	/* Pass off to hardware */

	if (!skb->xmit_more || netif_xmit_stopped(tx_queue->core_txq))

		efx_nic_push_buffers(tx_queue);



	efx_tx_maybe_stop_queue(tx_queue);



	tx_queue->tso_bursts++;

	return NETDEV_TX_OK;
@@ -1336,6 +1331,6 @@ static int efx_enqueue_skb_tso(struct efx_tx_queue *tx_queue, 
		dma_unmap_single(&efx->pci_dev->dev, state.header_dma_addr,

				 state.header_unmap_len, DMA_TO_DEVICE);



	efx_enqueue_unwind(tx_queue);

	efx_enqueue_unwind(tx_queue, old_insert_count);

	return NETDEV_TX_OK;

}