rt2x00: Improve TX status entry validation

The TX_STA_FIFO contains some information for identifying
a outgoing frame, however matching by WCID and ACK status is
not sufficient to 100% identify the macthing queue_entry structure
(containing the SKB buffer) which belongs to the status report.

Within TX_STA_FIFO we have a 4-bit field named PACKETID, which is
currently used to encode the queue id. The queue ID is however
limited to values from 0 to 3, which means 2 bits are sufficient
to encode the value. With the remaining 2 bits we can encode a
partial queue_entry index number. The value of PACKETID is not
allowed to become 0, with the queue ID ranging from 0 to 3, at least
one of the bits for the entry identification must be 1.

That leaves us with 3 possible values we can still encode in the
bits. Altough this doesn't allow 100% accurate matching of the
TX_STA_FIFO queue to a queue_entry structure, it at least improves
the accuracy. This allows us to better detect if we have missed the
TX_STA_FIFO report, which in turn reduces the number of watchdog
warnings regarding the TX status timeout.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rt2x00/rt2800lib.c b/drivers/net/wireless/rt2x00/rt2800lib.c
index 403e2ed..8e507d0 100644
--- a/drivers/net/wireless/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/rt2x00/rt2800lib.c
@@ -483,7 +483,8 @@
 			   txdesc->key_idx : 0xff);
 	rt2x00_set_field32(&word, TXWI_W1_MPDU_TOTAL_BYTE_COUNT,
 			   txdesc->length);
-	rt2x00_set_field32(&word, TXWI_W1_PACKETID, txdesc->qid + 1);
+	rt2x00_set_field32(&word, TXWI_W1_PACKETID_QUEUE, txdesc->qid);
+	rt2x00_set_field32(&word, TXWI_W1_PACKETID_ENTRY, (entry->entry_idx % 3) + 1);
 	rt2x00_desc_write(txwi, 1, word);
 
 	/*
@@ -708,7 +709,7 @@
 		 * Skip this entry when it contains an invalid
 		 * queue identication number.
 		 */
-		pid = rt2x00_get_field32(reg, TX_STA_FIFO_PID_TYPE) - 1;
+		pid = rt2x00_get_field32(reg, TX_STA_FIFO_PID_QUEUE);
 		if (pid >= QID_RX)
 			continue;