From: John Feeney <jfeeney@redhat.com>
Date: Fri, 17 Dec 2010 20:53:51 -0500
Subject: [net] bnx2: remove extra call to pci_map_page
Message-id: <4D0BCDDF.4020607@redhat.com>
Patchwork-id: 30669
O-Subject: [RHEL5.6 PATCH] bnx2: remove extra call to pci_map_page
Bugzilla: 663509
RH-Acked-by: Andy Gospodarek <gospo@redhat.com>
RH-Acked-by: David S. Miller <davem@redhat.com>
RH-Acked-by: Don Zickus <dzickus@redhat.com>

bz663509
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=663509
bnx2: calling pci_map_page() twice in tx path

Description of problem:
With IOMMU enabled, such as with PowerPC, error messages,
similar to the following, are written to the error log.

>bnx2 0003:01:00.1: iommu_alloc failed, tbl c000000001747b00 vaddr
> c000000393537000 npages 1
>

Upon review, it was noted that bnx2_start_xmit() was calling
pci_map_page() twice.

Solution:
In the RHEL5.4 time frame, code was added (bz475567) to mimic
skb_dma_map() which wasn't in RHEL5. This patch added a call to
pci_map_page(). It doesn't appear to me that this patch was
upstream.

During the RHEL5.6 update for bz568601, an upstream patch ("bnx2:
remove skb_dma_map/unmap calls from driver" Duyck commit:
e95524a726904a1d2b91552f0577838f67d53c6c) added a call to
pci_map_page(), too.

Hence we have two pci_map_page() calls in bnx2_start_xmit().
The solution is to remove the code added for RHEL5.4 and make
RHEL5.6 equivalent to upstream.

It should be noted that the RHEL5.4 patch added a variable
called dma_maps. The posted patch removes all references
to dma_maps upon the recommendation of the Broadcom bnx2
maintainer.

Upstream commit: n/a

Brew:
Successfully built in Brew for all architectures (task_2982677).

Testing:
Given that this is a RHEL5.6 show stopper for them, IBM is testing
this on PPC and reports success. Refer to the bz for specific
testing results, if desired.

Acks would be appreciated. Thanks.

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/drivers/net/bnx2.c b/drivers/net/bnx2.c
index 6974301..472385d 100644
--- a/drivers/net/bnx2.c
+++ b/drivers/net/bnx2.c
@@ -6395,7 +6395,6 @@ static int
 bnx2_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct bnx2 *bp = netdev_priv(dev);
-	dma_addr_t dma_maps[MAX_SKB_FRAGS + 1];
 	dma_addr_t mapping;
 	struct tx_bd *txbd;
 	struct sw_bd *tx_buf;
@@ -6466,21 +6465,7 @@ bnx2_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (pci_dma_mapping_error(mapping))
 		goto error;
 
-	dma_maps[0] = mapping;
-
 	last_frag = skb_shinfo(skb)->nr_frags;
-
-	for (i = 0; i < last_frag; i++) {
-		skb_frag_t *fp = &skb_shinfo(skb)->frags[i];
-
-		mapping = pci_map_page(bp->pdev, fp->page, fp->page_offset,
-				       fp->size, PCI_DMA_TODEVICE);
-		if (pci_dma_mapping_error(mapping))
-			goto map_unwind;
-		dma_maps[i + 1] = mapping;
-	}
-
-	mapping = dma_maps[0];
 	tx_buf = &txr->tx_buf_ring[ring_prod];
 	tx_buf->skb = skb;
 	tx_buf->nr_frags = last_frag;
@@ -6543,15 +6528,6 @@ bnx2_start_xmit(struct sk_buff *skb, struct net_device *dev)
 
 	return NETDEV_TX_OK;
 
-map_unwind:
-	while (--i >= 0) {
-		skb_frag_t *fp = &skb_shinfo(skb)->frags[i];
-
-		pci_unmap_page(bp->pdev, dma_maps[i + 1], fp->size,
-			       PCI_DMA_TODEVICE);
-	}
-	pci_unmap_single(bp->pdev, dma_maps[0], skb_headlen(skb),
-			 PCI_DMA_TODEVICE);
 error:
 	dev_kfree_skb(skb);
 	return NETDEV_TX_OK;