carl9170: allow users to lower output power level

This patch implements a simple way of reducing the
output power of the device by a configurable upper
limit.

Requested-by: Harshal Chhaya <harshal@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/ath/carl9170/mac.c

@@ -485,3 +485,38 @@ int carl9170_disable_key(struct ar9170 *ar, const u8 id)
 	return carl9170_exec_cmd(ar, CARL9170_CMD_DKEY,
 		sizeof(key), (u8 *)&key, 0, NULL);
 }
+
+int carl9170_set_mac_tpc(struct ar9170 *ar, struct ieee80211_channel *channel)
+{
+	unsigned int power, chains;
+
+	if (ar->eeprom.tx_mask != 1)
+		chains = AR9170_TX_PHY_TXCHAIN_2;
+	else
+		chains = AR9170_TX_PHY_TXCHAIN_1;
+
+	switch (channel->band) {
+	case IEEE80211_BAND_2GHZ:
+		power = ar->power_2G_ofdm[0] & 0x3f;
+		break;
+	case IEEE80211_BAND_5GHZ:
+		power = ar->power_5G_leg[0] & 0x3f;
+		break;
+	default:
+		BUG_ON(1);
+	}
+
+	power = min_t(unsigned int, power, ar->hw->conf.power_level * 2);
+
+	carl9170_regwrite_begin(ar);
+	carl9170_regwrite(AR9170_MAC_REG_ACK_TPC,
+			  0x3c1e | power << 20 | chains << 26);
+	carl9170_regwrite(AR9170_MAC_REG_RTS_CTS_TPC,
+			  power << 5 | chains << 11 |
+			  power << 21 | chains << 27);
+	carl9170_regwrite(AR9170_MAC_REG_CFEND_QOSNULL_TPC,
+			  power << 5 | chains << 11 |
+			  power << 21 | chains << 27);
+	carl9170_regwrite_finish();
+	return carl9170_regwrite_result();
+}