ath9k: fix PA linearization calibration related crash

Before PAPRD training can run, the card needs to have sent a packet for
thermal calibration. Sending a dummy packet with the PAPRD training flag
set causes a crash under some circumstance.
Fix the code by replacing the dummy tx with a delay that waits for a
real packet tx to have occurred.
Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

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

@@ -1775,6 +1775,8 @@ int ath9k_hw_reset(struct ath_hw *ah, struct ath9k_channel *chan,
 		/* Operating channel changed, reset channel calibration data */
 		memset(caldata, 0, sizeof(*caldata));
 		ath9k_init_nfcal_hist_buffer(ah, chan);
+	} else if (caldata) {
+		caldata->paprd_packet_sent = false;
 	}
 	ah->noise = ath9k_hw_getchan_noise(ah, chan);
 

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

@@ -405,6 +405,7 @@ struct ath9k_hw_cal_data {
 	int8_t iCoff;
 	int8_t qCoff;
 	bool rtt_done;
+	bool paprd_packet_sent;
 	bool paprd_done;
 	bool nfcal_pending;
 	bool nfcal_interference;

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

@@ -256,7 +256,7 @@ void ath_paprd_calibrate(struct work_struct *work)
 	int len = 1800;
 	int ret;
 
-	if (!caldata)
+	if (!caldata || !caldata->paprd_packet_sent || caldata->paprd_done)
 		return;
 
 	ath9k_ps_wakeup(sc);
@@ -283,13 +283,6 @@ void ath_paprd_calibrate(struct work_struct *work)
 			continue;
 
 		chain_ok = 0;
-
-		ath_dbg(common, CALIBRATE,
-			"Sending PAPRD frame for thermal measurement on chain %d\n",
-			chain);
-		if (!ath_paprd_send_frame(sc, skb, chain))
-			goto fail_paprd;
-
 		ar9003_paprd_setup_gain_table(ah, chain);
 
 		ath_dbg(common, CALIBRATE,

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

@@ -2018,6 +2018,9 @@ static void ath_tx_complete(struct ath_softc *sc, struct sk_buff *skb,
 
 	ath_dbg(common, XMIT, "TX complete: skb: %p\n", skb);
 
+	if (sc->sc_ah->caldata)
+		sc->sc_ah->caldata->paprd_packet_sent = true;
+
 	if (!(tx_flags & ATH_TX_ERROR))
 		/* Frame was ACKed */
 		tx_info->flags |= IEEE80211_TX_STAT_ACK;