[ 3.5.y.z extended stable ] Patch "ath9k: Test for TID only in BlockAcks while checking tx" has been added to staging queue

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Wed Dec 5 22:31:08 UTC 2012

This is a note to let you know that I have just added a patch titled

    ath9k: Test for TID only in BlockAcks while checking tx

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see



>From fbc42adc36604a9708a6c224400b3acabee9102b Mon Sep 17 00:00:00 2001
From: Sven Eckelmann <sven at narfation.org>
Date: Mon, 29 Oct 2012 13:25:20 +0100
Subject: [PATCH] ath9k: Test for TID only in BlockAcks while checking tx
X-Extended-Stable: 3.5

commit 6fe7cc71bbf3a0bc28c9cec3c00bc11e81344412 upstream.

The ath9k xmit functions for AMPDUs can send frames as non-aggregate in case
only one frame is currently available. The client will then answer using a
normal Ack instead of a BlockAck. This acknowledgement has no TID stored and
therefore the hardware is not able to provide us the corresponding TID.

The TID set by the hardware in the tx status descriptor has to be seen as
undefined and not as a valid TID value for normal acknowledgements. Doing
otherwise results in a massive amount of retransmissions and stalls of

Users may experience low bandwidth and complete connection stalls in
environments with transfers using multiple TIDs.

This regression was introduced in b11b160defc48e4daa283f785192ea3a23a51f8e
("ath9k: validate the TID in the tx status information").

Signed-off-by: Sven Eckelmann <sven at narfation.org>
Signed-off-by: Simon Wunderlich <siwu at hrz.tu-chemnitz.de>
Acked-by: Felix Fietkau <nbd at openwrt.org>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 drivers/net/wireless/ath/ath9k/xmit.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 11f252f..12a42f2 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -419,7 +419,7 @@ static void ath_tx_complete_aggr(struct ath_softc *sc, struct ath_txq *txq,
 	u16 seq_st = 0, acked_cnt = 0, txfail_cnt = 0, seq_first;
 	u32 ba[WME_BA_BMP_SIZE >> 5];
 	int isaggr, txfail, txpending, sendbar = 0, needreset = 0, nbad = 0;
-	bool rc_update = true;
+	bool rc_update = true, isba;
 	struct ieee80211_tx_rate rates[4];
 	struct ath_frame_info *fi;
 	int nframes;
@@ -463,13 +463,17 @@ static void ath_tx_complete_aggr(struct ath_softc *sc, struct ath_txq *txq,
 	tidno = ieee80211_get_qos_ctl(hdr)[0] & IEEE80211_QOS_CTL_TID_MASK;
 	tid = ATH_AN_2_TID(an, tidno);
 	seq_first = tid->seq_start;
+	isba = ts->ts_flags & ATH9K_TX_BA;

 	 * The hardware occasionally sends a tx status for the wrong TID.
 	 * In this case, the BA status cannot be considered valid and all
 	 * subframes need to be retransmitted
+	 *
+	 * Only BlockAcks have a TID and therefore normal Acks cannot be
+	 * checked
-	if (tidno != ts->tid)
+	if (isba && tidno != ts->tid)
 		txok = false;

 	isaggr = bf_isaggr(bf);

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