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>
diff --git a/drivers/net/wireless/ath/ath9k/hw.c b/drivers/net/wireless/ath/ath9k/hw.c
index 64a00d2..e4b9f35 100644
--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -1775,6 +1775,8 @@
 		/* 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);
 
diff --git a/drivers/net/wireless/ath/ath9k/hw.h b/drivers/net/wireless/ath/ath9k/hw.h
index ce7332c..6599a75 100644
--- a/drivers/net/wireless/ath/ath9k/hw.h
+++ b/drivers/net/wireless/ath/ath9k/hw.h
@@ -405,6 +405,7 @@
 	int8_t iCoff;
 	int8_t qCoff;
 	bool rtt_done;
+	bool paprd_packet_sent;
 	bool paprd_done;
 	bool nfcal_pending;
 	bool nfcal_interference;
diff --git a/drivers/net/wireless/ath/ath9k/link.c b/drivers/net/wireless/ath/ath9k/link.c
index 1c24192..825a29c 100644
--- a/drivers/net/wireless/ath/ath9k/link.c
+++ b/drivers/net/wireless/ath/ath9k/link.c
@@ -256,7 +256,7 @@
 	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 @@
 			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,
diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 2c9da6b..0d4155a 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -2018,6 +2018,9 @@
 
 	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;