rt2x00: Align ieee80211 header to 4-byte boundary for PCI devices

Some hardware require the ieee80211 header to be aligned to a
4-byte boundary before mapping it to the DMA. Otherwise some
frames (like beacons) will not be send out correctly by the
device.

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

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00queue.c b/drivers/net/wireless/rt2x00/rt2x00queue.c
index 65435c9fe4bc..e67e339d9dfd 100644
--- a/drivers/net/wireless/rt2x00/rt2x00queue.c
+++ b/drivers/net/wireless/rt2x00/rt2x00queue.c
@@ -453,9 +453,21 @@ int rt2x00queue_write_tx_frame(struct data_queue *queue, struct sk_buff *skb)
                         rt2x00crypto_tx_remove_iv(skb, &txdesc);
         }
 
+        /*
+         * When DMA allocation is required we should guarentee to the
+         * driver that the DMA is aligned to a 4-byte boundary.
+         * Aligning the header to this boundary can be done by calling
+         * rt2x00queue_payload_align with the header length of 0.
+         * However some drivers require L2 padding to pad the payload
+         * rather then the header. This could be a requirement for
+         * PCI and USB devices, while header alignment only is valid
+         * for PCI devices.
+         */
         if (test_bit(DRIVER_REQUIRE_L2PAD, &queue->rt2x00dev->flags))
                 rt2x00queue_payload_align(entry->skb, true,
                                           txdesc.header_length);
+        else if (test_bit(DRIVER_REQUIRE_DMA, &queue->rt2x00dev->flags))
+                rt2x00queue_payload_align(entry->skb, false, 0);
 
         /*
          * It could be possible that the queue was corrupted and this