netdev - [PATCH v3 01/10] net: eth: altera: tse_start_xmit ignores tx

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Message-Id: <20200604073256.25702-2-joyce.ooi@intel.com>
Date:   Thu,  4 Jun 2020 15:32:47 +0800
From:   "Ooi, Joyce" <joyce.ooi@...el.com>
To:     Thor Thayer <thor.thayer@...ux.intel.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dalon Westergreen <dalon.westergreen@...ux.intel.com>,
        Joyce Ooi <joyce.ooi@...el.com>,
        Tan Ley Foon <ley.foon.tan@...el.com>,
        See Chin Liang <chin.liang.see@...el.com>,
        Dinh Nguyen <dinh.nguyen@...el.com>,
        Dalon Westergreen <dalon.westergreen@...el.com>
Subject: [PATCH v3 01/10] net: eth: altera: tse_start_xmit ignores tx_buffer call response

From: Dalon Westergreen <dalon.westergreen@...el.com>

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 <dalon.westergreen@...el.com>
Signed-off-by: Joyce Ooi <joyce.ooi@...el.com>
---
v2: no change
v3: queue is stopped before returning NETDEV_TX_BUSY
---
 drivers/net/ethernet/altera/altera_sgdma.c    | 19 ++++++++++++-------
 drivers/net/ethernet/altera/altera_tse_main.c |  4 +++-
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/altera/altera_sgdma.c b/drivers/net/ethernet/altera/altera_sgdma.c
index db97170da8c7..fe6276c7e4a3 100644
--- a/drivers/net/ethernet/altera/altera_sgdma.c
+++ b/drivers/net/ethernet/altera/altera_sgdma.c
@@ -4,6 +4,7 @@
  */
 
 #include <linux/list.h>
+#include <linux/netdevice.h>
 #include "altera_utils.h"
 #include "altera_tse.h"
 #include "altera_sgdmahw.h"
@@ -159,10 +160,11 @@ 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)
 {
@@ -173,8 +175,11 @@ int sgdma_tx_buffer(struct altera_tse_private *priv, struct tse_buffer *buffer)
 	struct sgdma_descrip __iomem *ndesc = &descbase[1];
 
 	/* wait 'til the tx sgdma is ready for the next transmit request */
-	if (sgdma_txbusy(priv))
-		return 0;
+	if (sgdma_txbusy(priv)) {
+		if (!netif_queue_stopped(priv->dev))
+			netif_stop_queue(priv->dev);
+		return NETDEV_TX_BUSY;
+	}
 
 	sgdma_setup_descrip(cdesc,			/* current descriptor */
 			    ndesc,			/* next descriptor */
@@ -191,7 +196,7 @@ 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 1671c1f36691..2a9e6157a8a1 100644
--- a/drivers/net/ethernet/altera/altera_tse_main.c
+++ b/drivers/net/ethernet/altera/altera_tse_main.c
@@ -595,7 +595,9 @@ 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);
 
-- 
2.13.0