Currently we are always setting the tail address of descriptor list to the end of the pre-allocated list.
According to databook this is not correct. Tail address should point to the last available descriptor + 1, which means we have to update the tail address everytime we call the xmit function. This should make no impact in older versions of MAC but in newer versions there are some DMA features which allows the IP to fetch descriptors in advance and in a non sequential order so its critical that we set the tail address correctly. Signed-off-by: Jose Abreu <joab...@synopsys.com> Cc: David S. Miller <da...@davemloft.net> Cc: Joao Pinto <jpi...@synopsys.com> Cc: Giuseppe Cavallaro <peppe.cavall...@st.com> Cc: Alexandre Torgue <alexandre.tor...@st.com> --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index 1fca66ad6b17..14f890f2a970 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -2224,8 +2224,7 @@ static int stmmac_init_dma_engine(struct stmmac_priv *priv) stmmac_init_tx_chan(priv, priv->ioaddr, priv->plat->dma_cfg, tx_q->dma_tx_phy, chan); - tx_q->tx_tail_addr = tx_q->dma_tx_phy + - (DMA_TX_SIZE * sizeof(struct dma_desc)); + tx_q->tx_tail_addr = tx_q->dma_tx_phy; stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, chan); } @@ -3015,6 +3014,7 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev) netdev_tx_sent_queue(netdev_get_tx_queue(dev, queue), skb->len); + tx_q->tx_tail_addr = tx_q->dma_tx_phy + (tx_q->cur_tx * sizeof(*desc)); stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, queue); if (priv->tx_coal_timer && !tx_q->tx_timer_active) { @@ -3235,6 +3235,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev) stmmac_enable_dma_transmission(priv, priv->ioaddr); + tx_q->tx_tail_addr = tx_q->dma_tx_phy + (tx_q->cur_tx * sizeof(*desc)); stmmac_set_tx_tail_ptr(priv, priv->ioaddr, tx_q->tx_tail_addr, queue); if (priv->tx_coal_timer && !tx_q->tx_timer_active) { -- 2.7.4