[PATCH AUTOSEL 4.4 5/6] sis900: fix TX completion

From: Sasha Levin
Date: Tue Jul 02 2019 - 22:19:26 EST


From: Sergej Benilov <sergej.benilov@xxxxxxxxxxxxxx>

[ Upstream commit 8ac8a01092b2added0749ef937037bf1912e13e3 ]

Since commit 605ad7f184b60cfaacbc038aa6c55ee68dee3c89 "tcp: refine TSO autosizing",
outbound throughput is dramatically reduced for some connections, as sis900
is doing TX completion within idle states only.

Make TX completion happen after every transmitted packet.

Test:
netperf

before patch:
> netperf -H remote -l -2000000 -- -s 1000000
MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to 95.223.112.76 () port 0 AF_INET : demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

87380 327680 327680 253.44 0.06

after patch:
> netperf -H remote -l -10000000 -- -s 1000000
MIGRATED TCP STREAM TEST from 0.0.0.0 () port 0 AF_INET to 95.223.112.76 () port 0 AF_INET : demo
Recv Send Send
Socket Socket Message Elapsed
Size Size Size Time Throughput
bytes bytes bytes secs. 10^6bits/sec

87380 327680 327680 5.38 14.89

Thx to Dave Miller and Eric Dumazet for helpful hints

Signed-off-by: Sergej Benilov <sergej.benilov@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/net/ethernet/sis/sis900.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/sis/sis900.c b/drivers/net/ethernet/sis/sis900.c
index fd812d2e5e1c..dff5b56738d3 100644
--- a/drivers/net/ethernet/sis/sis900.c
+++ b/drivers/net/ethernet/sis/sis900.c
@@ -1058,7 +1058,7 @@ sis900_open(struct net_device *net_dev)
sis900_set_mode(sis_priv, HW_SPEED_10_MBPS, FDX_CAPABLE_HALF_SELECTED);

/* Enable all known interrupts by setting the interrupt mask. */
- sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE);
+ sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE | TxDESC);
sw32(cr, RxENA | sr32(cr));
sw32(ier, IE);

@@ -1581,7 +1581,7 @@ static void sis900_tx_timeout(struct net_device *net_dev)
sw32(txdp, sis_priv->tx_ring_dma);

/* Enable all known interrupts by setting the interrupt mask. */
- sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE);
+ sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE | TxDESC);
}

/**
@@ -1621,7 +1621,7 @@ sis900_start_xmit(struct sk_buff *skb, struct net_device *net_dev)
spin_unlock_irqrestore(&sis_priv->lock, flags);
return NETDEV_TX_OK;
}
- sis_priv->tx_ring[entry].cmdsts = (OWN | skb->len);
+ sis_priv->tx_ring[entry].cmdsts = (OWN | INTR | skb->len);
sw32(cr, TxENA | sr32(cr));

sis_priv->cur_tx ++;
@@ -1677,7 +1677,7 @@ static irqreturn_t sis900_interrupt(int irq, void *dev_instance)
do {
status = sr32(isr);

- if ((status & (HIBERR|TxURN|TxERR|TxIDLE|RxORN|RxERR|RxOK)) == 0)
+ if ((status & (HIBERR|TxURN|TxERR|TxIDLE|TxDESC|RxORN|RxERR|RxOK)) == 0)
/* nothing intresting happened */
break;
handled = 1;
@@ -1687,7 +1687,7 @@ static irqreturn_t sis900_interrupt(int irq, void *dev_instance)
/* Rx interrupt */
sis900_rx(net_dev);

- if (status & (TxURN | TxERR | TxIDLE))
+ if (status & (TxURN | TxERR | TxIDLE | TxDESC))
/* Tx interrupt */
sis900_finish_xmit(net_dev);

@@ -1899,8 +1899,8 @@ static void sis900_finish_xmit (struct net_device *net_dev)

if (tx_status & OWN) {
/* The packet is not transmitted yet (owned by hardware) !
- * Note: the interrupt is generated only when Tx Machine
- * is idle, so this is an almost impossible case */
+ * Note: this is an almost impossible condition
+ * in case of TxDESC ('descriptor interrupt') */
break;
}

@@ -2476,7 +2476,7 @@ static int sis900_resume(struct pci_dev *pci_dev)
sis900_set_mode(sis_priv, HW_SPEED_10_MBPS, FDX_CAPABLE_HALF_SELECTED);

/* Enable all known interrupts by setting the interrupt mask. */
- sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE);
+ sw32(imr, RxSOVR | RxORN | RxERR | RxOK | TxURN | TxERR | TxIDLE | TxDESC);
sw32(cr, RxENA | sr32(cr));
sw32(ier, IE);

--
2.20.1