On Mon, 2020-10-19 at 16:57 +0800, Dylan Hung wrote:
> These rules must be followed when accessing the TX descriptor:
>
> 1. A TX descriptor is "cleanable" only when its value is non-zero
> and the owner bit is set to "software"
Can you elaborate ? What is the point of that change ? The owner bit
should be sufficient, why do we need to check other fields ?
> 2. A TX descriptor is "writable" only when its value is zero
> regardless the edotr mask.
Again, why is that ? Can you elaborate ? What race are you trying to
address here ?
Cheers,
Ben.
> Fixes: 52c0cae87465 ("ftgmac100: Remove tx descriptor accessors")
> Signed-off-by: Dylan Hung <dylan_h...@aspeedtech.com>
> Signed-off-by: Joel Stanley <j...@jms.id.au>
> ---
> drivers/net/ethernet/faraday/ftgmac100.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/net/ethernet/faraday/ftgmac100.c
> b/drivers/net/ethernet/faraday/ftgmac100.c
> index 00024dd41147..7cacbe4aecb7 100644
> --- a/drivers/net/ethernet/faraday/ftgmac100.c
> +++ b/drivers/net/ethernet/faraday/ftgmac100.c
> @@ -647,6 +647,9 @@ static bool ftgmac100_tx_complete_packet(struct
> ftgmac100 *priv)
> if (ctl_stat & FTGMAC100_TXDES0_TXDMA_OWN)
> return false;
>
> + if ((ctl_stat & ~(priv->txdes0_edotr_mask)) == 0)
> + return false;
> +
> skb = priv->tx_skbs[pointer];
> netdev->stats.tx_packets++;
> netdev->stats.tx_bytes += skb->len;
> @@ -756,6 +759,9 @@ static netdev_tx_t
> ftgmac100_hard_start_xmit(struct sk_buff *skb,
> pointer = priv->tx_pointer;
> txdes = first = &priv->txdes[pointer];
>
> + if (le32_to_cpu(txdes->txdes0) & ~priv->txdes0_edotr_mask)
> + goto drop;
> +
> /* Setup it up with the packet head. Don't write the head to
> the
> * ring just yet
> */
> @@ -787,6 +793,10 @@ static netdev_tx_t
> ftgmac100_hard_start_xmit(struct sk_buff *skb,
> /* Setup descriptor */
> priv->tx_skbs[pointer] = skb;
> txdes = &priv->txdes[pointer];
> +
> + if (le32_to_cpu(txdes->txdes0) & ~priv-
> >txdes0_edotr_mask)
> + goto dma_err;
> +
> ctl_stat = ftgmac100_base_tx_ctlstat(priv, pointer);
> ctl_stat |= FTGMAC100_TXDES0_TXDMA_OWN;
> ctl_stat |= FTGMAC100_TXDES0_TXBUF_SIZE(len);
