netdev - [PATCH 14/14] Spidernet Rework RX linked list

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Message-ID: <20061213212505.GN1915@austin.ibm.com>
Date:	Wed, 13 Dec 2006 15:25:05 -0600
From:	linas@...tin.ibm.com (Linas Vepstas)
To:	Andrew Morton <akpm@...l.org>
Cc:	netdev@...r.kernel.org, linuxppc-dev@...abs.org, jgarzik@...ox.com,
	Christoph Hellwig <hch@...radead.org>,
	Ishizaki Kou <kou.ishizaki@...hiba.co.jp>,
	Jens Osterkamp <Jens.Osterkamp@....de>,
	James K Lewis <jim@...ewis.com>,
	Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 14/14] Spidernet Rework RX linked list


Make the hardware perceive the RX descriptor ring as a 
null-terminated linked list, instead of a circular ring.

Signed-off-by: Linas Vepstas <linas@...tin.ibm.com>
Cc: James K Lewis <jklewis@...ibm.com>
Cc: Arnd Bergmann <arnd@...db.de>

----
 drivers/net/spider_net.c |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

Index: linux-2.6.19-git7/drivers/net/spider_net.c
===================================================================
--- linux-2.6.19-git7.orig/drivers/net/spider_net.c	2006-12-13 14:32:13.000000000 -0600
+++ linux-2.6.19-git7/drivers/net/spider_net.c	2006-12-13 14:33:21.000000000 -0600
@@ -419,9 +419,13 @@ spider_net_prepare_rx_descr(struct spide
 		card->spider_stats.rx_iommu_map_error++;
 		descr->dmac_cmd_status = SPIDER_NET_DESCR_NOT_IN_USE;
 	} else {
+		descr->next_descr_addr = 0;
 		wmb();
 		descr->dmac_cmd_status = SPIDER_NET_DESCR_CARDOWNED |
 					 SPIDER_NET_DMAC_NOINTR_COMPLETE;
+
+		wmb();
+		descr->prev->next_descr_addr = descr->bus_addr;
 	}
 
 	return 0;
@@ -1650,7 +1654,6 @@ int
 spider_net_open(struct net_device *netdev)
 {
 	struct spider_net_card *card = netdev_priv(netdev);
-	struct spider_net_descr *descr;
 	int result;
 
 	result = spider_net_init_chain(card, &card->tx_chain);
@@ -1662,13 +1665,6 @@ spider_net_open(struct net_device *netde
 	if (result)
 		goto alloc_rx_failed;
 
-	/* Make a ring of of bus addresses */
-	descr = card->rx_chain.ring;
-	do {
-		descr->next_descr_addr = descr->next->bus_addr;
-		descr = descr->next;
-	} while (descr != card->rx_chain.ring);
-
 	/* Allocate rx skbs */
 	if (spider_net_alloc_rx_skbs(card))
 		goto alloc_skbs_failed;
-
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