From: Rob Herring <rob.herr...@calxeda.com>
Since the xgmac transmit start and completion work locklessly, it is
possible for xgmac_xmit to stop the tx queue after the xgmac_tx_complete
has run resulting in the tx queue never being woken up. Fix this by
ensuring that ring buffer index updates are visible and serialize the
queue wake with netif_tx_lock.
The implementation used here was copied from
drivers/net/ethernet/broadcom/tg3.c.
Signed-off-by: Rob Herring <rob.herr...@calxeda.com>
---
drivers/net/ethernet/calxeda/xgmac.c | 25 +++++++++++++++++++------
1 file changed, 19 insertions(+), 6 deletions(-)
diff --git a/drivers/net/ethernet/calxeda/xgmac.c
b/drivers/net/ethernet/calxeda/xgmac.c
index f630855..cd5872c 100644
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -410,6 +410,9 @@ struct xgmac_priv {
#define dma_ring_space(h, t, s) CIRC_SPACE(h, t, s)
#define dma_ring_cnt(h, t, s) CIRC_CNT(h, t, s)
+#define tx_dma_ring_space(p) \
+ dma_ring_space((p)->tx_head, (p)->tx_tail, DMA_TX_RING_SZ)
+
/* XGMAC Descriptor Access Helpers */
static inline void desc_set_buf_len(struct xgmac_dma_desc *p, u32 buf_sz)
{
@@ -886,9 +889,14 @@ static void xgmac_tx_complete(struct xgmac_priv *priv)
priv->tx_tail = dma_ring_incr(entry, DMA_TX_RING_SZ);
}
- if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) >
- MAX_SKB_FRAGS)
- netif_wake_queue(priv->dev);
+ /* Ensure tx_tail is visible to xgmac_xmit */
+ smp_mb();
+ if (unlikely(netif_queue_stopped(priv->dev))) {
+ netif_tx_lock(priv->dev);
+ if (tx_dma_ring_space(priv) > MAX_SKB_FRAGS)
+ netif_wake_queue(priv->dev);
+ netif_tx_unlock(priv->dev);
+ }
}
static void xgmac_tx_timeout_work(struct work_struct *work)
@@ -1125,10 +1133,15 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb,
struct net_device *dev)
priv->tx_head = dma_ring_incr(entry, DMA_TX_RING_SZ);
- if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) <
- MAX_SKB_FRAGS)
+ /* Ensure tx_head update is visible to tx completion */
+ smp_mb();
+ if (unlikely(tx_dma_ring_space(priv) < MAX_SKB_FRAGS)) {
netif_stop_queue(dev);
-
+ /* Ensure netif_stop_queue is visible to tx completion */
+ smp_mb();
+ if (tx_dma_ring_space(priv) > MAX_SKB_FRAGS)
+ netif_wake_queue(dev);
+ }
return NETDEV_TX_OK;
}
--
1.8.1.2
--
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