netdev - [PATCH v2 net-next 2/6] sfc: make ef100 xmit_more handling look more like ef10's

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Date:   Thu, 3 Sep 2020 22:34:42 +0100
From:   Edward Cree <ecree@...arflare.com>
To:     <linux-net-drivers@...arflare.com>, <davem@...emloft.net>
CC:     <netdev@...r.kernel.org>
Subject: [PATCH v2 net-next 2/6] sfc: make ef100 xmit_more handling look more
 like ef10's

This should cause no functional change; merely make there only be one
 design of xmit_more handling to understand.  As with the EF10/Siena
 version, we set tx_queue->xmit_pending when we queue up a TX, and
 clear it when we ring the doorbell (in ef100_notify_tx_desc).
While we're at it, make ef100_notify_tx_desc static since nothing
 outside of ef100_tx.c uses it.

Signed-off-by: Edward Cree <ecree@...arflare.com>
---
 drivers/net/ethernet/sfc/ef100_tx.c | 22 +++++++++++-----------
 drivers/net/ethernet/sfc/ef100_tx.h |  1 -
 2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/sfc/ef100_tx.c b/drivers/net/ethernet/sfc/ef100_tx.c
index 8d478c5e720e..ce1b462efd17 100644
--- a/drivers/net/ethernet/sfc/ef100_tx.c
+++ b/drivers/net/ethernet/sfc/ef100_tx.c
@@ -117,11 +117,13 @@ static efx_oword_t *ef100_tx_desc(struct efx_tx_queue *tx_queue, unsigned int in
 		return NULL;
 }
 
-void ef100_notify_tx_desc(struct efx_tx_queue *tx_queue)
+static void ef100_notify_tx_desc(struct efx_tx_queue *tx_queue)
 {
 	unsigned int write_ptr;
 	efx_dword_t reg;
 
+	tx_queue->xmit_pending = false;
+
 	if (unlikely(tx_queue->notify_count == tx_queue->write_count))
 		return;
 
@@ -131,7 +133,6 @@ void ef100_notify_tx_desc(struct efx_tx_queue *tx_queue)
 	efx_writed_page(tx_queue->efx, &reg,
 			ER_GZ_TX_RING_DOORBELL, tx_queue->queue);
 	tx_queue->notify_count = tx_queue->write_count;
-	tx_queue->xmit_pending = false;
 }
 
 static void ef100_tx_push_buffers(struct efx_tx_queue *tx_queue)
@@ -372,15 +373,14 @@ int ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
 			netif_tx_start_queue(tx_queue->core_txq);
 	}
 
-	if (__netdev_tx_sent_queue(tx_queue->core_txq, skb->len, xmit_more))
-		tx_queue->xmit_pending = false; /* push doorbell */
-	else if (tx_queue->write_count - tx_queue->notify_count > 255)
-		/* Ensure we never push more than 256 packets at once */
-		tx_queue->xmit_pending = false; /* push */
-	else
-		tx_queue->xmit_pending = true; /* don't push yet */
+	tx_queue->xmit_pending = true;
 
-	if (!tx_queue->xmit_pending)
+	/* If xmit_more then we don't need to push the doorbell, unless there
+	 * are 256 descriptors already queued in which case we have to push to
+	 * ensure we never push more than 256 at once.
+	 */
+	if (__netdev_tx_sent_queue(tx_queue->core_txq, skb->len, xmit_more) ||
+	    tx_queue->write_count - tx_queue->notify_count > 255)
 		ef100_tx_push_buffers(tx_queue);
 
 	if (segments) {
@@ -399,7 +399,7 @@ int ef100_enqueue_skb(struct efx_tx_queue *tx_queue, struct sk_buff *skb)
 
 	/* If we're not expecting another transmit and we had something to push
 	 * on this queue then we need to push here to get the previous packets
-	 * out.  We only enter this branch from before the 'Update BQL' section
+	 * out.  We only enter this branch from before the xmit_more handling
 	 * above, so xmit_pending still refers to the old state.
 	 */
 	if (tx_queue->xmit_pending && !xmit_more)
diff --git a/drivers/net/ethernet/sfc/ef100_tx.h b/drivers/net/ethernet/sfc/ef100_tx.h
index fa23e430bdd7..ddc4b98fa6db 100644
--- a/drivers/net/ethernet/sfc/ef100_tx.h
+++ b/drivers/net/ethernet/sfc/ef100_tx.h
@@ -17,7 +17,6 @@
 int ef100_tx_probe(struct efx_tx_queue *tx_queue);
 void ef100_tx_init(struct efx_tx_queue *tx_queue);
 void ef100_tx_write(struct efx_tx_queue *tx_queue);
-void ef100_notify_tx_desc(struct efx_tx_queue *tx_queue);
 unsigned int ef100_tx_max_skb_descs(struct efx_nic *efx);
 
 void ef100_ev_tx(struct efx_channel *channel, const efx_qword_t *p_event);