ath9k: fix bug in tx power

commit 841051602e3fa18ea468fe5a177aa92b6eb44b56 upstream.

The ath9k driver subtracts 3 dBm to the txpower as with two radios the
signal power is doubled.
The resulting value is assigned in an u16 which overflows and makes
the card work at full power.

Signed-off-by: Matteo Croce <matteo@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/net/wireless/ath/ath9k/eeprom_def.c b/drivers/net/wireless/ath/ath9k/eeprom_def.c
index afa2b73ddbdde865bb91491f283dd7eceb6cdf49..a48eb570a47cc6c0756658681f3952f8766bc15c 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/eeprom_def.c
+++ b/drivers/net/wireless/ath/ath9k/eeprom_def.c
@@ -1062,15 +1062,19 @@ static void ath9k_hw_set_def_power_per_rate_table(struct ath_hw *ah,
        case 1:
                break;
        case 2:
-               scaledPower -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
+               if (scaledPower > REDUCE_SCALED_POWER_BY_TWO_CHAIN)
+                       scaledPower -= REDUCE_SCALED_POWER_BY_TWO_CHAIN;
+               else
+                       scaledPower = 0;
                break;
        case 3:
-               scaledPower -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
+               if (scaledPower > REDUCE_SCALED_POWER_BY_THREE_CHAIN)
+                       scaledPower -= REDUCE_SCALED_POWER_BY_THREE_CHAIN;
+               else
+                       scaledPower = 0;
                break;
        }
 
-       scaledPower = max((u16)0, scaledPower);
-
        if (IS_CHAN_2GHZ(chan)) {
                numCtlModes = ARRAY_SIZE(ctlModesFor11g) -
                        SUB_NUM_CTL_MODES_AT_2G_40;