fm10k: Limit dma sync of RX buffers to actual packet size

On packet RX, we perform a dma sync for cpu before passing the
packet up.  Here we limit that sync to the actual length of the
incoming packet, rather than always syncing the entire buffer.

Signed-off-by: Scott Peterson <scott.d.peterson@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/fm10k/fm10k_main.c

@@ -251,6 +251,7 @@ static bool fm10k_can_reuse_rx_page(struct fm10k_rx_buffer *rx_buffer,
 /**
  * fm10k_add_rx_frag - Add contents of Rx buffer to sk_buff
  * @rx_buffer: buffer containing page to add
+ * @size: packet size from rx_desc
  * @rx_desc: descriptor containing length of buffer written by hardware
  * @skb: sk_buff to place the data into
  *
@@ -263,12 +264,12 @@ static bool fm10k_can_reuse_rx_page(struct fm10k_rx_buffer *rx_buffer,
  * true if the buffer can be reused by the interface.
  **/
 static bool fm10k_add_rx_frag(struct fm10k_rx_buffer *rx_buffer,
+			      unsigned int size,
 			      union fm10k_rx_desc *rx_desc,
 			      struct sk_buff *skb)
 {
 	struct page *page = rx_buffer->page;
 	unsigned char *va = page_address(page) + rx_buffer->page_offset;
-	unsigned int size = le16_to_cpu(rx_desc->w.length);
 #if (PAGE_SIZE < 8192)
 	unsigned int truesize = FM10K_RX_BUFSZ;
 #else
@@ -314,6 +315,7 @@ static struct sk_buff *fm10k_fetch_rx_buffer(struct fm10k_ring *rx_ring,
 					     union fm10k_rx_desc *rx_desc,
 					     struct sk_buff *skb)
 {
+	unsigned int size = le16_to_cpu(rx_desc->w.length);
 	struct fm10k_rx_buffer *rx_buffer;
 	struct page *page;
 
@@ -350,11 +352,11 @@ static struct sk_buff *fm10k_fetch_rx_buffer(struct fm10k_ring *rx_ring,
 	dma_sync_single_range_for_cpu(rx_ring->dev,
 				      rx_buffer->dma,
 				      rx_buffer->page_offset,
-				      FM10K_RX_BUFSZ,
+				      size,
 				      DMA_FROM_DEVICE);
 
 	/* pull page into skb */
-	if (fm10k_add_rx_frag(rx_buffer, rx_desc, skb)) {
+	if (fm10k_add_rx_frag(rx_buffer, size, rx_desc, skb)) {
 		/* hand second half of page back to the ring */
 		fm10k_reuse_rx_page(rx_ring, rx_buffer);
 	} else {