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GRETH: GBit transmit descriptor handling optimization

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It is safe to enable all fragments before enabling the first descriptor,
this way all descriptors don't have to be processed twice, added extra
memory barrier.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Hellstrom 2011-01-14 03:02:39 +00:00 committed by David S. Miller
parent bbe9e63733
commit 2a2bc012b9
1 changed files with 10 additions and 9 deletions
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19
drivers/net/greth.c
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@ -503,7 +503,7 @@ greth_start_xmit_gbit(struct sk_buff *skb, struct net_device *dev)
greth->tx_skbuff[curr_tx] = NULL;
bdp = greth->tx_bd_base + curr_tx;
status = GRETH_TXBD_CSALL;
status = GRETH_TXBD_CSALL | GRETH_BD_EN;
status |= frag->size & GRETH_BD_LEN;
/* Wrap around descriptor ring */
@ -540,26 +540,27 @@ greth_start_xmit_gbit(struct sk_buff *skb, struct net_device *dev)
wmb();
/* Enable the descriptors that we configured ... */
for (i = 0; i < nr_frags + 1; i++) {
bdp = greth->tx_bd_base + greth->tx_next;
greth_write_bd(&bdp->stat, greth_read_bd(&bdp->stat) | GRETH_BD_EN);
greth->tx_next = NEXT_TX(greth->tx_next);
greth->tx_free--;
}
/* Enable the descriptor chain by enabling the first descriptor */
bdp = greth->tx_bd_base + greth->tx_next;
greth_write_bd(&bdp->stat, greth_read_bd(&bdp->stat) | GRETH_BD_EN);
greth->tx_next = curr_tx;
greth->tx_free -= nr_frags + 1;
wmb();
greth_enable_tx(greth);
return NETDEV_TX_OK;
frag_map_error:
/* Unmap SKB mappings that succeeded */
/* Unmap SKB mappings that succeeded and disable descriptor */
for (i = 0; greth->tx_next + i != curr_tx; i++) {
bdp = greth->tx_bd_base + greth->tx_next + i;
dma_unmap_single(greth->dev,
greth_read_bd(&bdp->addr),
greth_read_bd(&bdp->stat) & GRETH_BD_LEN,
DMA_TO_DEVICE);
greth_write_bd(&bdp->stat, 0);
}
map_error:
if (net_ratelimit())