linux-kernel - [PATCH 3.16 013/294] net: bcmgenet: update ring producer index and buffer count in xmit

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Date:   Mon, 06 Nov 2017 23:03:02 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Florian Fainelli" <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        "Petri Gynther" <pgynther@...gle.com>
Subject: [PATCH 3.16 013/294] net: bcmgenet: update ring producer index
 and buffer count in xmit

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Fainelli <f.fainelli@...il.com>

commit ae67bf0188cbb9d1786bdfcca9e1976cb36ee327 upstream.

There is no need to have both bcmgenet_xmit_single() and
bcmgenet_xmit_frag() perform a free_bds decrement and a prod_index
increment by one. In case one of these functions fails to map a SKB or
fragment for transmit, we will return and exit bcmgenet_xmit() with an
error.

We can therefore safely use our local copy of nr_frags to know by how
much we should decrement the number of free buffers available, and by
how much the producer count must be incremented and do this in the tail
of bcmgenet_xmit().

Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
Acked-by: Petri Gynther <pgynther@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 18 +++++-------------
 1 file changed, 5 insertions(+), 13 deletions(-)

--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1071,11 +1071,6 @@ static int bcmgenet_xmit_single(struct n
 
 	dmadesc_set(priv, tx_cb_ptr->bd_addr, mapping, length_status);
 
-	/* Decrement total BD count and advance our write pointer */
-	ring->free_bds -= 1;
-	ring->prod_index += 1;
-	ring->prod_index &= DMA_P_INDEX_MASK;
-
 	return 0;
 }
 
@@ -1113,11 +1108,6 @@ static int bcmgenet_xmit_frag(struct net
 			(frag->size << DMA_BUFLENGTH_SHIFT) | dma_desc_flags |
 			(priv->hw_params->qtag_mask << DMA_TX_QTAG_SHIFT));
 
-
-	ring->free_bds -= 1;
-	ring->prod_index += 1;
-	ring->prod_index &= DMA_P_INDEX_MASK;
-
 	return 0;
 }
 
@@ -1258,9 +1248,11 @@ static netdev_tx_t bcmgenet_xmit(struct
 
 	skb_tx_timestamp(skb);
 
-	/* we kept a software copy of how much we should advance the TDMA
-	 * producer index, now write it down to the hardware
-	 */
+	/* Decrement total BD count and advance our write pointer */
+	ring->free_bds -= nr_frags + 1;
+	ring->prod_index += nr_frags + 1;
+	ring->prod_index &= DMA_P_INDEX_MASK;
+
 	bcmgenet_tdma_ring_writel(priv, ring->index,
 			ring->prod_index, TDMA_PROD_INDEX);