[PATCH 16/16] Spidernet Rework RX linked list

[Linas Vepstas]

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 at austin.ibm.com>
Cc: James K Lewis <jklewis at us.ibm.com>
Cc: Arnd Bergmann <arnd at arndb.de>

----
 drivers/net/spider_net.c |   10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

Index: linux-2.6.19-git7/drivers/net/spider_net.c
===================================================================
--- linux-2.6.19-git7.orig/drivers/net/spider_net.c	2006-12-06 16:03:20.000000000 -0600
+++ linux-2.6.19-git7/drivers/net/spider_net.c	2006-12-06 16:05:48.000000000 -0600
@@ -389,9 +389,13 @@ 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;
@@ -1676,12 +1680,6 @@ spider_net_open(struct net_device *netde
 					+ card->num_tx_desc * sizeof(struct spider_net_descr),
 	                          card->num_rx_desc);
 
-	descr = card->rx_chain.head;
-	do {
-		descr->next_descr_addr = descr->next->bus_addr;
-		descr = descr->next;
-	} while (descr != card->rx_chain.head);
-
 	/* allocate rx skbs */
 	if (spider_net_alloc_rx_skbs(card))
 		goto alloc_skbs_failed;