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Commit 2a2bc012 authored by Daniel Hellstrom's avatar Daniel Hellstrom Committed by David S. Miller
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GRETH: GBit transmit descriptor handling optimization 



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: default avatarDaniel Hellstrom <daniel@gaisler.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent bbe9e637

drivers/net/greth.c

+10 −9
Original line number Diff line number Diff line
@@ -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++) {

	/* 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 = NEXT_TX(greth->tx_next);

		greth->tx_free--;

	}

	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())