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Subject[PATCH net-next] net: stmmac: add BQL support
Date
Add support for Byte Queue Limits to the STMicro MAC driver.

Tested on a Amlogic S805 Cortex-A5 board, where the use of BQL
slightly decreases the ping latency from ~10ms to ~3ms when the
100Mbps link is saturated by TCP streams. No difference is
observed at 1Gbps.

Signed-off-by: Beniamino Galvani <b.galvani@gmail.com>
---
drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 118a427..c5af3d8 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1097,6 +1097,7 @@ static int init_dma_desc_rings(struct net_device *dev, gfp_t flags)

priv->dirty_tx = 0;
priv->cur_tx = 0;
+ netdev_reset_queue(priv->dev);

stmmac_clear_descriptors(priv);

@@ -1300,6 +1301,7 @@ static void stmmac_dma_operation_mode(struct stmmac_priv *priv)
static void stmmac_tx_clean(struct stmmac_priv *priv)
{
unsigned int txsize = priv->dma_tx_size;
+ unsigned int bytes_compl = 0, pkts_compl = 0;

spin_lock(&priv->tx_lock);

@@ -1356,6 +1358,8 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)
priv->hw->mode->clean_desc3(priv, p);

if (likely(skb != NULL)) {
+ pkts_compl++;
+ bytes_compl += skb->len;
dev_consume_skb_any(skb);
priv->tx_skbuff[entry] = NULL;
}
@@ -1364,6 +1368,9 @@ static void stmmac_tx_clean(struct stmmac_priv *priv)

priv->dirty_tx++;
}
+
+ netdev_completed_queue(priv->dev, pkts_compl, bytes_compl);
+
if (unlikely(netif_queue_stopped(priv->dev) &&
stmmac_tx_avail(priv) > STMMAC_TX_THRESH(priv))) {
netif_tx_lock(priv->dev);
@@ -1418,6 +1425,7 @@ static void stmmac_tx_err(struct stmmac_priv *priv)
(i == txsize - 1));
priv->dirty_tx = 0;
priv->cur_tx = 0;
+ netdev_reset_queue(priv->dev);
priv->hw->dma->start_tx(priv->ioaddr);

priv->dev->stats.tx_errors++;
@@ -2049,6 +2057,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
skb_tx_timestamp(skb);

priv->hw->dma->enable_dma_transmission(priv->ioaddr);
+ netdev_sent_queue(dev, skb->len);

spin_unlock(&priv->tx_lock);
return NETDEV_TX_OK;
--
2.1.4


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