rt2x00: Map extra_tx_headroom to DMA

If a driver requests additional headroom it should
be mapped to DMA as well because it will be send to
the hardware as well (as form of extra descriptor).

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 21 insertions, 3 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index d10a8012f387..2822684c505e 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -100,8 +100,21 @@ void rt2x00queue_map_txskb(struct rt2x00_dev *rt2x00dev, struct sk_buff *skb)
 {
         struct skb_frame_desc *skbdesc = get_skb_frame_desc(skb);
 
-        skbdesc->skb_dma = dma_map_single(rt2x00dev->dev, skb->data, skb->len,
-                                          DMA_TO_DEVICE);
+        /*
+         * If device has requested headroom, we should make sure that
+         * is also mapped to the DMA so it can be used for transfering
+         * additional descriptor information to the hardware.
+         */
+        skb_push(skb, rt2x00dev->hw->extra_tx_headroom);
+
+        skbdesc->skb_dma =
+            dma_map_single(rt2x00dev->dev, skb->data, skb->len, DMA_TO_DEVICE);
+
+        /*
+         * Restore data pointer to original location again.
+         */
+        skb_pull(skb, rt2x00dev->hw->extra_tx_headroom);
+
         skbdesc->flags |= SKBDESC_DMA_MAPPED_TX;
 }
 EXPORT_SYMBOL_GPL(rt2x00queue_map_txskb);
@@ -117,7 +130,12 @@ void rt2x00queue_unmap_skb(struct rt2x00_dev *rt2x00dev, struct sk_buff *skb)
         }
 
         if (skbdesc->flags & SKBDESC_DMA_MAPPED_TX) {
-                dma_unmap_single(rt2x00dev->dev, skbdesc->skb_dma, skb->len,
+                /*
+                 * Add headroom to the skb length, it has been removed
+                 * by the driver, but it was actually mapped to DMA.
+                 */
+                dma_unmap_single(rt2x00dev->dev, skbdesc->skb_dma,
+                                 skb->len + rt2x00dev->hw->extra_tx_headroom,
                                  DMA_TO_DEVICE);
                 skbdesc->flags &= ~SKBDESC_DMA_MAPPED_TX;
         }