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

Thor Thayer
2020-07-23T16:31:53Z

On 7/8/20 2:23 AM, Ooi, Joyce wrote:
> 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);
>
>
Reviewed-by: Thor Thayer <thor.thayer@linux.intel.com>