[PATCH 3.5 35/64] rt2800: fix wrong TX power compensation

[Luis Henriques]

3.5.7.24 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stanislaw Gruszka <sgruszka at redhat.com>

commit 6e956da2027c767859128b9bfef085cf2a8e233b upstream.

We should not do temperature compensation on devices without
EXTERNAL_TX_ALC bit set (called DynamicTxAgcControl on vendor driver).
Such devices can have totally bogus TSSI parameters on the EEPROM,
but still threaded by us as valid and result doing wrong TX power
calculations.

This fix inability to connect to AP on slightly longer distance on
some Ralink chips/devices.

Reported-and-tested-by: Fabien ADAM <id2ndr at crocobox.org>
Signed-off-by: Stanislaw Gruszka <sgruszka at redhat.com>
Signed-off-by: John W. Linville <linville at tuxdriver.com>
[ luis: backported to 3.5:
  - use rt2x00_eeprom_read() instead of rt2800_eeprom_read() ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/net/wireless/rt2x00/rt2800lib.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/wireless/rt2x00/rt2800lib.c b/drivers/net/wireless/rt2x00/rt2800lib.c
index 1c60904..b81f2b6 100644
--- a/drivers/net/wireless/rt2x00/rt2800lib.c
+++ b/drivers/net/wireless/rt2x00/rt2800lib.c
@@ -2181,6 +2181,13 @@ static int rt2800_get_gain_calibration_delta(struct rt2x00_dev *rt2x00dev)
 	int i;
 
 	/*
+	 * First check if temperature compensation is supported.
+	 */
+	rt2x00_eeprom_read(rt2x00dev, EEPROM_NIC_CONF1, &eeprom);
+	if (!rt2x00_get_field16(eeprom, EEPROM_NIC_CONF1_EXTERNAL_TX_ALC))
+		return 0;
+
+	/*
 	 * Read TSSI boundaries for temperature compensation from
 	 * the EEPROM.
 	 *
-- 
1.8.3.2