spidernet: invalidate unused pointer.

Invalidate a pointer as its pci_unmap'ed; this is a bit of
paranoia to make sure hardware doesn't continue trying to
DMA to it.
Signed-off-by: NLinas Vepstas <linas@austin.ibm.com>
Signed-off-by: NJeff Garzik <jeff@garzik.org>

drivers/net/spider_net.c

@@ -1187,6 +1187,7 @@ spider_net_decode_one_descr(struct spider_net_card *card)
 	struct spider_net_descr_chain *chain = &card->rx_chain;
 	struct spider_net_descr *descr = chain->tail;
 	struct spider_net_hw_descr *hwdescr = descr->hwdescr;
+	u32 hw_buf_addr;
 	int status;
 
 	status = spider_net_get_descr_status(hwdescr);
@@ -1200,7 +1201,9 @@ spider_net_decode_one_descr(struct spider_net_card *card)
 	chain->tail = descr->next;
 
 	/* unmap descriptor */
-	pci_unmap_single(card->pdev, hwdescr->buf_addr,
+	hw_buf_addr = hwdescr->buf_addr;
+	hwdescr->buf_addr = 0xffffffff;
+	pci_unmap_single(card->pdev, hw_buf_addr,
 			SPIDER_NET_MAX_FRAME, PCI_DMA_FROMDEVICE);
 
 	if ( (status == SPIDER_NET_DESCR_RESPONSE_ERROR) ||
@@ -1235,7 +1238,7 @@ spider_net_decode_one_descr(struct spider_net_card *card)
 	if (hwdescr->dmac_cmd_status & 0xfcf4) {
 		dev_err(&card->netdev->dev, "bad status, cmd_status=x%08x\n",
 			       hwdescr->dmac_cmd_status);
-		pr_err("buf_addr=x%08x\n", hwdescr->buf_addr);
+		pr_err("buf_addr=x%08x\n", hw_buf_addr);
 		pr_err("buf_size=x%08x\n", hwdescr->buf_size);
 		pr_err("next_descr_addr=x%08x\n", hwdescr->next_descr_addr);
 		pr_err("result_size=x%08x\n", hwdescr->result_size);