ath9k_hw: fix invalid extension channel noisefloor readings in HT20

When the hardware is configured in HT20 mode, noise floor readings for
the extension channel often return invalid values, which keep the
values in the NF history buffer at the hardware-specific maximum limit.
Fix this by discarding the extension channel values when in HT20 mode.

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/ar5008_phy.c b/drivers/net/wireless/ath/ath9k/ar5008_phy.c
index 4a910b7..3d2c867 100644
--- a/drivers/net/wireless/ath/ath9k/ar5008_phy.c
+++ b/drivers/net/wireless/ath/ath9k/ar5008_phy.c
@@ -1506,6 +1506,9 @@
 	nf = MS(REG_READ(ah, AR_PHY_CH2_CCA), AR_PHY_CH2_MINCCA_PWR);
 	nfarray[2] = sign_extend(nf, 9);
 
+	if (!IS_CHAN_HT40(ah->curchan))
+		return;
+
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR_PHY_EXT_MINCCA_PWR);
 	nfarray[3] = sign_extend(nf, 9);
 
diff --git a/drivers/net/wireless/ath/ath9k/ar9002_phy.c b/drivers/net/wireless/ath/ath9k/ar9002_phy.c
index 4922b8d..adbf031 100644
--- a/drivers/net/wireless/ath/ath9k/ar9002_phy.c
+++ b/drivers/net/wireless/ath/ath9k/ar9002_phy.c
@@ -477,7 +477,8 @@
 	nfarray[0] = sign_extend(nf, 9);
 
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR9280_PHY_EXT_MINCCA_PWR);
-	nfarray[3] = sign_extend(nf, 9);
+	if (IS_CHAN_HT40(ah->curchan))
+		nfarray[3] = sign_extend(nf, 9);
 
 	if (AR_SREV_9285(ah) || AR_SREV_9271(ah))
 		return;
@@ -486,7 +487,8 @@
 	nfarray[1] = sign_extend(nf, 9);
 
 	nf = MS(REG_READ(ah, AR_PHY_CH1_EXT_CCA), AR9280_PHY_CH1_EXT_MINCCA_PWR);
-	nfarray[4] = sign_extend(nf, 9);
+	if (IS_CHAN_HT40(ah->curchan))
+		nfarray[4] = sign_extend(nf, 9);
 }
 
 static void ar9002_hw_set_nf_limits(struct ath_hw *ah)
diff --git a/drivers/net/wireless/ath/ath9k/ar9003_phy.c b/drivers/net/wireless/ath/ath9k/ar9003_phy.c
index 7c93338..a753a43 100644
--- a/drivers/net/wireless/ath/ath9k/ar9003_phy.c
+++ b/drivers/net/wireless/ath/ath9k/ar9003_phy.c
@@ -1029,6 +1029,9 @@
 	nf = MS(REG_READ(ah, AR_PHY_CCA_2), AR_PHY_CH2_MINCCA_PWR);
 	nfarray[2] = sign_extend(nf, 9);
 
+	if (!IS_CHAN_HT40(ah->curchan))
+		return;
+
 	nf = MS(REG_READ(ah, AR_PHY_EXT_CCA), AR_PHY_EXT_MINCCA_PWR);
 	nfarray[3] = sign_extend(nf, 9);