ath9k: fix stopping tx dma on reset

In some situations, stopping Tx DMA frequently fails, leading to messages
like this:

ath: Failed to stop TX DMA in 100 msec after killing last frame
ath: Failed to stop TX DMA!

This patch uses a few MAC features to abort DMA globally instead of iterating
over all hardware queues and attempting to stop them individually.
Not only is that faster and works with a shorter timeout, it also makes the
process much more reliable.

With this change, I can no longer trigger these messages on AR9380,
and on AR9280 they become much more rare.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/mac.c

@@ -143,6 +143,34 @@ bool ath9k_hw_updatetxtriglevel(struct ath_hw *ah, bool bIncTrigLevel)
 }
 EXPORT_SYMBOL(ath9k_hw_updatetxtriglevel);
 
+void ath9k_hw_abort_tx_dma(struct ath_hw *ah)
+{
+	int i, q;
+
+	REG_WRITE(ah, AR_Q_TXD, AR_Q_TXD_M);
+
+	REG_SET_BIT(ah, AR_PCU_MISC, AR_PCU_FORCE_QUIET_COLL | AR_PCU_CLEAR_VMF);
+	REG_SET_BIT(ah, AR_DIAG_SW, AR_DIAG_FORCE_CH_IDLE_HIGH);
+	REG_SET_BIT(ah, AR_D_GBL_IFS_MISC, AR_D_GBL_IFS_MISC_IGNORE_BACKOFF);
+
+	for (q = 0; q < AR_NUM_QCU; q++) {
+		for (i = 0; i < 1000; i++) {
+			if (i)
+				udelay(5);
+
+			if (!ath9k_hw_numtxpending(ah, q))
+				break;
+		}
+	}
+
+	REG_CLR_BIT(ah, AR_PCU_MISC, AR_PCU_FORCE_QUIET_COLL | AR_PCU_CLEAR_VMF);
+	REG_CLR_BIT(ah, AR_DIAG_SW, AR_DIAG_FORCE_CH_IDLE_HIGH);
+	REG_CLR_BIT(ah, AR_D_GBL_IFS_MISC, AR_D_GBL_IFS_MISC_IGNORE_BACKOFF);
+
+	REG_WRITE(ah, AR_Q_TXD, 0);
+}
+EXPORT_SYMBOL(ath9k_hw_abort_tx_dma);
+
 bool ath9k_hw_stoptxdma(struct ath_hw *ah, u32 q)
 {
 #define ATH9K_TX_STOP_DMA_TIMEOUT	4000    /* usec */

drivers/net/wireless/ath/ath9k/mac.h

@@ -677,6 +677,7 @@ void ath9k_hw_cleartxdesc(struct ath_hw *ah, void *ds);
 u32 ath9k_hw_numtxpending(struct ath_hw *ah, u32 q);
 bool ath9k_hw_updatetxtriglevel(struct ath_hw *ah, bool bIncTrigLevel);
 bool ath9k_hw_stoptxdma(struct ath_hw *ah, u32 q);
+void ath9k_hw_abort_tx_dma(struct ath_hw *ah);
 void ath9k_hw_gettxintrtxqs(struct ath_hw *ah, u32 *txqs);
 bool ath9k_hw_set_txq_props(struct ath_hw *ah, int q,
 			    const struct ath9k_tx_queue_info *qinfo);

drivers/net/wireless/ath/ath9k/xmit.c

@@ -1194,16 +1194,14 @@ bool ath_drain_all_txq(struct ath_softc *sc, bool retry_tx)
 	if (sc->sc_flags & SC_OP_INVALID)
 		return true;
 
-	/* Stop beacon queue */
-	ath9k_hw_stoptxdma(sc->sc_ah, sc->beacon.beaconq);
+	ath9k_hw_abort_tx_dma(ah);
 
-	/* Stop data queues */
+	/* Check if any queue remains active */
 	for (i = 0; i < ATH9K_NUM_TX_QUEUES; i++) {
-		if (ATH_TXQ_SETUP(sc, i)) {
-			txq = &sc->tx.txq[i];
-			ath9k_hw_stoptxdma(ah, txq->axq_qnum);
-			npend += ath9k_hw_numtxpending(ah, txq->axq_qnum);
-		}
+		if (!ATH_TXQ_SETUP(sc, i))
+			continue;
+
+		npend += ath9k_hw_numtxpending(ah, sc->tx.txq[i].axq_qnum);
 	}
 
 	if (npend)