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: NFelix Fietkau <nbd@openwrt.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/ath9k/ar5008_phy.c

@@ -1506,6 +1506,9 @@ static void ar5008_hw_do_getnf(struct ath_hw *ah,
 	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);
 

drivers/net/wireless/ath/ath9k/ar9002_phy.c

@@ -477,7 +477,8 @@ static void ar9002_hw_do_getnf(struct ath_hw *ah,
 	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 @@ static void ar9002_hw_do_getnf(struct ath_hw *ah,
 	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)

drivers/net/wireless/ath/ath9k/ar9003_phy.c

@@ -1029,6 +1029,9 @@ static void ar9003_hw_do_getnf(struct ath_hw *ah,
 	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);