[PATCH v4 01/10] net: eth: altera: tse_start_xmit ignores tx_buffer call response

Ooi, Joyce
2020-07-08T07:24:49Z

From: Dalon Westergreen <dalon.westergreen@intel.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@intel.com>
Signed-off-by: Joyce Ooi <joyce.ooi@intel.com>
---
v2: no change
v3: queue is stopped before returning NETDEV_TX_BUSY
v4: no change
---
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 907125abef2c..ec2b36e05c3f 100644
--- a/drivers/net/ethernet/altera/altera_tse_main.c
+++ b/drivers/net/ethernet/altera/altera_tse_main.c
@@ -595,7 +595,9 @@ static netdev_tx_t 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