Subject: [PATCH net-next 1/8] net: eth: altera: tse_start_xmit ignores tx_buffer call response

From: Dalon Westergreen <[email-masked]>
Date: Wed, 14 Nov 2018 16:50:40 -0800

From: Dalon Westergreen <[email-masked]>

The return from tx_buffer call in tse_start_xmit is
inapropriately ignored.  tse_buffer calls should return
0 for success or NETDEV_TX_BUSY.  tse_start_xmit should
return not report a successful transmit when the tse_buffer
call returns an error condition.

In addition to the above, the msgdma and sgdma do not return
the same value on success or failure.  The sgdma_tx_buffer
returned 0 on failure and a positive number of transmitted
packets on success.  Given that it only ever sends 1 packet,
this made no sense.  The msgdma implementation msgdma_tx_buffer
returns 0 on success.

  -> Don't ignore the return from tse_buffer calls
  -> Fix sgdma tse_buffer call to return 0 on success
     and NETDEV_TX_BUSY on failure.

Signed-off-by: Dalon Westergreen <[email-masked]>
---
 drivers/net/ethernet/altera/altera_sgdma.c    | 14 ++++++++------
 drivers/net/ethernet/altera/altera_tse_main.c |  4 +++-
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/altera/altera_sgdma.c b/drivers/net/ethernet/altera/altera_sgdma.c
index 88ef67a998b4..eb47b9b820bb 100644
--- a/drivers/net/ethernet/altera/altera_sgdma.c
+++ b/drivers/net/ethernet/altera/altera_sgdma.c
@@ -15,6 +15,7 @@
  */
 
 #include <linux/list.h>
+#include <linux/netdevice.h>
 #include "altera_utils.h"
 #include "altera_tse.h"
 #include "altera_sgdmahw.h"
@@ -170,10 +171,11 @@ void sgdma_clear_txirq(struct altera_tse_private *priv)
 		    SGDMA_CTRLREG_CLRINT);
 }
 
-/* transmits buffer through SGDMA. Returns number of buffers
- * transmitted, 0 if not possible.
- *
- * tx_lock is held by the caller
+/* transmits buffer through SGDMA.
+ *   original behavior returned the number of transmitted packets (always 1) &
+ *   returned 0 on error.  This differs from the msgdma.  the calling function
+ *   will now actually look at the code, so from now, 0 is good and return
+ *   NETDEV_TX_BUSY when busy.
  */
 int sgdma_tx_buffer(struct altera_tse_private *priv, struct tse_buffer *buffer)
 {
@@ -185,7 +187,7 @@ int sgdma_tx_buffer(struct altera_tse_private *priv, struct tse_buffer *buffer)
 
 	/* wait 'til the tx sgdma is ready for the next transmit request */
 	if (sgdma_txbusy(priv))
-		return 0;
+		return NETDEV_TX_BUSY;
 
 	sgdma_setup_descrip(cdesc,			/* current descriptor */
 			    ndesc,			/* next descriptor */
@@ -202,7 +204,7 @@ int sgdma_tx_buffer(struct altera_tse_private *priv, struct tse_buffer *buffer)
 	/* enqueue the request to the pending transmit queue */
 	queue_tx(priv, buffer);
 
-	return 1;
+	return 0;
 }

diff --git a/drivers/net/ethernet/altera/altera_tse_main.c b/drivers/net/ethernet/altera/altera_tse_main.c
index baca8f704a45..dcb330129e23 100644
--- a/drivers/net/ethernet/altera/altera_tse_main.c
+++ b/drivers/net/ethernet/altera/altera_tse_main.c
@@ -606,7 +606,9 @@ static int tse_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	buffer->dma_addr = dma_addr;
 	buffer->len = nopaged_len;
 
-	priv->dmaops->tx_buffer(priv, buffer);
+	ret = priv->dmaops->tx_buffer(priv, buffer);
+	if (ret)
+		goto out;
 
 	skb_tx_timestamp(skb);
 
-- 
2.19.1