From: Felix Fietkau <nbd@nbd.name>
Date: Wed, 19 Jul 2017 08:49:31 +0200
Subject: [PATCH] ath9k: adjust tx power reduction for US regulatory
 domain

FCC regulatory rules allow for up to 3 dBi antenna gain. Account for
this in the EEPROM based tx power reduction code.

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/drivers/net/wireless/ath/ath9k/hw.c
+++ b/drivers/net/wireless/ath/ath9k/hw.c
@@ -2954,6 +2954,10 @@ void ath9k_hw_apply_txpower(struct ath_h
 	if (ant_gain > max_gain)
 		ant_reduction = ant_gain - max_gain;
 
+	/* FCC allows maximum antenna gain of 3 dBi */
+	if (reg->region == NL80211_DFS_FCC)
+		ant_reduction = min_t(int, ant_reduction - 6, 0);
+
 	ah->eep_ops->set_txpower(ah, chan, ctl, ant_reduction, new_pwr, test);
 }