rt2x00: Fix rt2800 USB TX Path DMA issue

rt2800usb chips need to add 1~3 bytes zero padding after each 802.11 header & payload,
and at the end need to add 4 bytes zero padding whether doing TX bulk aggregation or not,

TXINFO_W0_USB_DMA_TX_PKT_LEN in TXINFO must include 1-3 bytes padding after 802.11 header & payload
but do not include 4 bytes end zero padding.

In rt2800usb_get_tx_data_len do not consider multiple of the USB packet size case, sometimes this will
cause USB DMA problem.

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

1 files changed, 26 insertions, 13 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2800usb.c b/drivers/net/wireless/rt2x00/rt2800usb.c
index 2933bf1d74bb..935b76d3ce4f 100644
--- a/drivers/net/wireless/rt2x00/rt2800usb.c
+++ b/drivers/net/wireless/rt2x00/rt2800usb.c
@@ -307,8 +307,14 @@ static void rt2800usb_write_tx_desc(struct queue_entry *entry,
          * Initialize TXINFO descriptor
          */
         rt2x00_desc_read(txi, 0, &word);
+
+        /*
+         * The size of TXINFO_W0_USB_DMA_TX_PKT_LEN is
+         * TXWI + 802.11 header + L2 pad + payload + pad,
+         * so need to decrease size of TXINFO and USB end pad.
+         */
         rt2x00_set_field32(&word, TXINFO_W0_USB_DMA_TX_PKT_LEN,
-                           entry->skb->len - TXINFO_DESC_SIZE);
+                           entry->skb->len - TXINFO_DESC_SIZE - 4);
         rt2x00_set_field32(&word, TXINFO_W0_WIV,
                            !test_bit(ENTRY_TXD_ENCRYPT_IV, &txdesc->flags));
         rt2x00_set_field32(&word, TXINFO_W0_QSEL, 2);
@@ -326,22 +332,29 @@ static void rt2800usb_write_tx_desc(struct queue_entry *entry,
         skbdesc->desc_len = TXINFO_DESC_SIZE + TXWI_DESC_SIZE;
 }
 
-/*
- * TX data initialization
- */
-static int rt2800usb_get_tx_data_len(struct queue_entry *entry)
+static void rt2800usb_write_tx_data(struct queue_entry *entry,
+                                        struct txentry_desc *txdesc)
 {
-        int length;
+        u8 padding_len;
 
         /*
-         * The length _must_ include 4 bytes padding,
-         * it should always be multiple of 4,
-         * but it must _not_ be a multiple of the USB packet size.
+         * pad(1~3 bytes) is added after each 802.11 payload.
+         * USB end pad(4 bytes) is added at each USB bulk out packet end.
+         * TX frame format is :
+         * | TXINFO | TXWI | 802.11 header | L2 pad | payload | pad | USB end pad |
+         *                 |<------------- tx_pkt_len ------------->|
          */
-        length = roundup(entry->skb->len + 4, 4);
-        length += (4 * !(length % entry->queue->usb_maxpacket));
+        rt2800_write_tx_data(entry, txdesc);
+        padding_len = roundup(entry->skb->len + 4, 4) - entry->skb->len;
+        memset(skb_put(entry->skb, padding_len), 0, padding_len);
+}
 
-        return length;
+/*
+ * TX data initialization
+ */
+static int rt2800usb_get_tx_data_len(struct queue_entry *entry)
+{
+        return entry->skb->len;
 }
 
 /*
@@ -579,7 +592,7 @@ static const struct rt2x00lib_ops rt2800usb_rt2x00_ops = {
         .link_tuner             = rt2800_link_tuner,
         .watchdog               = rt2800usb_watchdog,
         .write_tx_desc          = rt2800usb_write_tx_desc,
-        .write_tx_data          = rt2800_write_tx_data,
+        .write_tx_data          = rt2800usb_write_tx_data,
         .write_beacon           = rt2800_write_beacon,
         .get_tx_data_len        = rt2800usb_get_tx_data_len,
         .kick_tx_queue          = rt2x00usb_kick_tx_queue,