[PATCH 5/6] net: calxedaxgmac: rework transmit ring handling

Rob Herring
2012-10-12T15:16:33Z

Only generate tx interrupts on every ring size / 4 descriptors. Move the
netif_stop_queue call to the end of the xmit function rather than
checking at the beginning.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
---
drivers/net/ethernet/calxeda/xgmac.c | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index 4a1a06a..5cb10b6 100644
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -374,6 +374,7 @@ struct xgmac_priv {
struct sk_buff **tx_skbuff;
unsigned int tx_head;
unsigned int tx_tail;
+ int tx_irq_cnt;

void __iomem *base;
unsigned int dma_buf_sz;
@@ -886,7 +887,7 @@ static void xgmac_tx_complete(struct xgmac_priv *priv)
}

if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) >
- TX_THRESH)
+ MAX_SKB_FRAGS)
netif_wake_queue(priv->dev);
}

@@ -1057,19 +1058,15 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
struct xgmac_priv *priv = netdev_priv(dev);
unsigned int entry;
int i;
+ u32 irq_flag;
int nfrags = skb_shinfo(skb)->nr_frags;
struct xgmac_dma_desc *desc, *first;
unsigned int desc_flags;
unsigned int len;
dma_addr_t paddr;

- if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) <
- (nfrags + 1)) {
- writel(DMA_INTR_DEFAULT_MASK | DMA_INTR_ENA_TIE,
- priv->base + XGMAC_DMA_INTR_ENA);
- netif_stop_queue(dev);
- return NETDEV_TX_BUSY;
- }
+ priv->tx_irq_cnt = (priv->tx_irq_cnt + 1) & (DMA_TX_RING_SZ/4 - 1);
+ irq_flag = priv->tx_irq_cnt ? 0 : TXDESC_INTERRUPT;

desc_flags = (skb->ip_summed == CHECKSUM_PARTIAL) ?
TXDESC_CSUM_ALL : 0;
@@ -1110,9 +1107,9 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
/* Interrupt on completition only for the latest segment */
if (desc != first)
desc_set_tx_owner(desc, desc_flags |
- TXDESC_LAST_SEG | TXDESC_INTERRUPT);
+ TXDESC_LAST_SEG | irq_flag);
else
- desc_flags |= TXDESC_LAST_SEG | TXDESC_INTERRUPT;
+ desc_flags |= TXDESC_LAST_SEG | irq_flag;

/* Set owner on first desc last to avoid race condition */
wmb();
@@ -1121,6 +1118,9 @@ 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);

writel(1, priv->base + XGMAC_DMA_TX_POLL);
+ if (dma_ring_space(priv->tx_head, priv->tx_tail, DMA_TX_RING_SZ) <
+ MAX_SKB_FRAGS)
+ netif_stop_queue(dev);

return NETDEV_TX_OK;
}
@@ -1397,7 +1397,7 @@ static irqreturn_t xgmac_interrupt(int irq, void *dev_id)
}

/* TX/RX NORMAL interrupts */
- if (intr_status & (DMA_STATUS_RI | DMA_STATUS_TU)) {
+ if (intr_status & (DMA_STATUS_RI | DMA_STATUS_TU | DMA_STATUS_TI)) {
writel_relaxed(DMA_INTR_ABNORMAL, priv->base + XGMAC_DMA_INTR_ENA);
napi_schedule(&priv->napi);
}
--
1.7.9.5