cassini: Use page_address() instead of kmap_atomic()

Pages for Rx buffers are allocated in cas_page_alloc() using either
GFP_ATOMIC or GFP_KERNEL. Memory allocated with GFP_KERNEL/GFP_ATOMIC can't
come from highmem and so there's no need to kmap() them. Just use
page_address() instead. This makes the variable 'addr' unnecessary, so
remove it too.

Note that kmap_atomic() disables preemption and page-fault processing,
but page_address() doesn't. When removing uses of kmap_atomic(), one has to
check if the code being executed between the map/unmap implicitly depends
on page-faults and/or preemption being disabled. If yes, then code to
disable page-faults and/or preemption should also be added for functional
correctness. That however doesn't appear to be the case here, so just
page_address() is used.

I don't have hardware, so this change has only been compile tested.

Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/cassini.c

@@ -1915,7 +1915,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 	int off, swivel = RX_SWIVEL_OFF_VAL;
 	struct cas_page *page;
 	struct sk_buff *skb;
-	void *addr, *crcaddr;
+	void *crcaddr;
 	__sum16 csum;
 	char *p;
 
@@ -1936,7 +1936,7 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 	skb_reserve(skb, swivel);
 
 	p = skb->data;
-	addr = crcaddr = NULL;
+	crcaddr = NULL;
 	if (hlen) { /* always copy header pages */
 		i = CAS_VAL(RX_COMP2_HDR_INDEX, words[1]);
 		page = cp->rx_pages[CAS_VAL(RX_INDEX_RING, i)][CAS_VAL(RX_INDEX_NUM, i)];
@@ -1948,12 +1948,10 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 			i += cp->crc_size;
 		dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr + off,
 					i, DMA_FROM_DEVICE);
-		addr = cas_page_map(page->buffer);
-		memcpy(p, addr + off, i);
+		memcpy(p, page_address(page->buffer) + off, i);
 		dma_sync_single_for_device(&cp->pdev->dev,
 					   page->dma_addr + off, i,
 					   DMA_FROM_DEVICE);
-		cas_page_unmap(addr);
 		RX_USED_ADD(page, 0x100);
 		p += hlen;
 		swivel = 0;
@@ -1984,12 +1982,11 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 		/* make sure we always copy a header */
 		swivel = 0;
 		if (p == (char *) skb->data) { /* not split */
-			addr = cas_page_map(page->buffer);
-			memcpy(p, addr + off, RX_COPY_MIN);
+			memcpy(p, page_address(page->buffer) + off,
+			       RX_COPY_MIN);
 			dma_sync_single_for_device(&cp->pdev->dev,
 						   page->dma_addr + off, i,
 						   DMA_FROM_DEVICE);
-			cas_page_unmap(addr);
 			off += RX_COPY_MIN;
 			swivel = RX_COPY_MIN;
 			RX_USED_ADD(page, cp->mtu_stride);
@@ -2036,10 +2033,8 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 			RX_USED_ADD(page, hlen + cp->crc_size);
 		}
 
-		if (cp->crc_size) {
-			addr = cas_page_map(page->buffer);
-			crcaddr  = addr + off + hlen;
-		}
+		if (cp->crc_size)
+			crcaddr = page_address(page->buffer) + off + hlen;
 
 	} else {
 		/* copying packet */
@@ -2061,12 +2056,10 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 			i += cp->crc_size;
 		dma_sync_single_for_cpu(&cp->pdev->dev, page->dma_addr + off,
 					i, DMA_FROM_DEVICE);
-		addr = cas_page_map(page->buffer);
-		memcpy(p, addr + off, i);
+		memcpy(p, page_address(page->buffer) + off, i);
 		dma_sync_single_for_device(&cp->pdev->dev,
 					   page->dma_addr + off, i,
 					   DMA_FROM_DEVICE);
-		cas_page_unmap(addr);
 		if (p == (char *) skb->data) /* not split */
 			RX_USED_ADD(page, cp->mtu_stride);
 		else
@@ -2081,20 +2074,17 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 						page->dma_addr,
 						dlen + cp->crc_size,
 						DMA_FROM_DEVICE);
-			addr = cas_page_map(page->buffer);
-			memcpy(p, addr, dlen + cp->crc_size);
+			memcpy(p, page_address(page->buffer), dlen + cp->crc_size);
 			dma_sync_single_for_device(&cp->pdev->dev,
 						   page->dma_addr,
 						   dlen + cp->crc_size,
 						   DMA_FROM_DEVICE);
-			cas_page_unmap(addr);
 			RX_USED_ADD(page, dlen + cp->crc_size);
 		}
 end_copy_pkt:
-		if (cp->crc_size) {
-			addr    = NULL;
+		if (cp->crc_size)
 			crcaddr = skb->data + alloclen;
-		}
+
 		skb_put(skb, alloclen);
 	}
 
@@ -2103,8 +2093,6 @@ static int cas_rx_process_pkt(struct cas *cp, struct cas_rx_comp *rxc,
 		/* checksum includes FCS. strip it out. */
 		csum = csum_fold(csum_partial(crcaddr, cp->crc_size,
 					      csum_unfold(csum)));
-		if (addr)
-			cas_page_unmap(addr);
 	}
 	skb->protocol = eth_type_trans(skb, cp->dev);
 	if (skb->protocol == htons(ETH_P_IP)) {