[PATCH net v3 1/3] net: bcmgenet: fix off-by-one in bcmgenet_put_txcb

[Justin Chen <justin.chen@broadcom.com>]

The write_ptr points to the next open tx_cb. We want to return the
tx_cb that gets rewinded, so we must rewind the pointer first then
return the tx_cb that it points to. That way the txcb can be correctly
cleaned up.

Fixes: 876dbadd53a7 ("net: bcmgenet: Fix unmapping of fragments in bcmgenet_xmit()")
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
---
 drivers/net/ethernet/broadcom/genet/bcmgenet.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 482a31e7b72b..0f6e4baba25b 100644
--- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
+++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
@@ -1819,15 +1819,15 @@ static struct enet_cb *bcmgenet_put_txcb(struct bcmgenet_priv *priv,
 {
 	struct enet_cb *tx_cb_ptr;
 
-	tx_cb_ptr = ring->cbs;
-	tx_cb_ptr += ring->write_ptr - ring->cb_ptr;
-
 	/* Rewinding local write pointer */
 	if (ring->write_ptr == ring->cb_ptr)
 		ring->write_ptr = ring->end_ptr;
 	else
 		ring->write_ptr--;
 
+	tx_cb_ptr = ring->cbs;
+	tx_cb_ptr += ring->write_ptr - ring->cb_ptr;
+
 	return tx_cb_ptr;
 }
 
-- 
2.34.1