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Date:   Wed, 2 Sep 2020 15:35:53 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH net-next 1/5] sfc: add and use efx_tx_send_pending in tx.c

Instead of using efx_tx_queue_partner(), which relies on the assumption
 that tx_queues_per_channel is 2, efx_tx_send_pending() iterates over
 txqs with efx_for_each_channel_tx_queue().

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 drivers/net/ethernet/sfc/tx.c | 59 ++++++++++++++++++-----------------
 1 file changed, 31 insertions(+), 28 deletions(-)

diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index 727201d5eb24..71eb99db5439 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -268,6 +268,19 @@ static int efx_enqueue_skb_pio(struct efx_tx_queue *tx_queue,
 }
 #endif /* EFX_USE_PIO */
 
+/* Send any pending traffic for a channel. xmit_more is shared across all
+ * queues for a channel, so we must check all of them.
+ */
+static void efx_tx_send_pending(struct efx_channel *channel)
+{
+	struct efx_tx_queue *q;
+
+	efx_for_each_channel_tx_queue(q, channel) {
+		if (q->xmit_more_available)
+			efx_nic_push_buffers(q);
+	}
+}
+
 /*
  * Add a socket buffer to a TX queue
  *
@@ -336,21 +349,11 @@ netdev_tx_t __efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb
 
 	efx_tx_maybe_stop_queue(tx_queue);
 
-	/* Pass off to hardware */
-	if (__netdev_tx_sent_queue(tx_queue->core_txq, skb_len, xmit_more)) {
-		struct efx_tx_queue *txq2 = efx_tx_queue_partner(tx_queue);
-
-		/* There could be packets left on the partner queue if
-		 * xmit_more was set. If we do not push those they
-		 * could be left for a long time and cause a netdev watchdog.
-		 */
-		if (txq2->xmit_more_available)
-			efx_nic_push_buffers(txq2);
+	tx_queue->xmit_more_available = true;
 
-		efx_nic_push_buffers(tx_queue);
-	} else {
-		tx_queue->xmit_more_available = xmit_more;
-	}
+	/* Pass off to hardware */
+	if (__netdev_tx_sent_queue(tx_queue->core_txq, skb_len, xmit_more))
+		efx_tx_send_pending(tx_queue->channel);
 
 	if (segments) {
 		tx_queue->tso_bursts++;
@@ -371,14 +374,8 @@ netdev_tx_t __efx_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb
 	 * on this queue or a partner queue then we need to push here to get the
 	 * previous packets out.
 	 */
-	if (!xmit_more) {
-		struct efx_tx_queue *txq2 = efx_tx_queue_partner(tx_queue);
-
-		if (txq2->xmit_more_available)
-			efx_nic_push_buffers(txq2);
-
-		efx_nic_push_buffers(tx_queue);
-	}
+	if (!xmit_more)
+		efx_tx_send_pending(tx_queue->channel);
 
 	return NETDEV_TX_OK;
 }
@@ -489,18 +486,24 @@ netdev_tx_t efx_hard_start_xmit(struct sk_buff *skb,
 
 	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;
 	}
+
+	/* PTP "event" packet */
+	if (unlikely(efx_xmit_with_hwtstamp(skb)) &&
+	    unlikely(efx_ptp_is_ptp_tx(efx, skb))) {
+		/* There may be existing transmits on the channel that are
+		 * waiting for this packet to trigger the doorbell write.
+		 * We need to send the packets at this point.
+		 */
+		efx_tx_send_pending(efx_get_tx_channel(efx, index));
+		return efx_ptp_tx(efx, skb);
+	}
+
 	tx_queue = efx_get_tx_queue(efx, index, type);
 
 	return __efx_enqueue_skb(tx_queue, skb);

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