commit d6756d0dc220c3d12e2c4c06ca97d1dbcb5edf4e
author Igor Perminov <igor.perminov@inbox.ru> Mon Aug 10 00:58:54 2009 +0200
committer John W. Linville <linville@tuxdriver.com> Fri Aug 14 09:13:55 2009 -0400
tree aaa10e86a291624fa71cde855860a7787bb49d2e
parent 3281d95d0535909e28ff16c38a678102e10f0312

rt2x00: Fix beacon de-synchronization while update beacon

When beacon is being updated to refresh TIM (AP mode), beacon frames are
de-synchronizing (i.e. two neighbor beacon frames - before and after
update - are being transmitted with a wrong time interval).
That is because xxx_write_beacon should disable beacon generation only
while beacon data are being uploaded to the device, but it should not
disable the beacon clock.

Signed-off-by: Igor Perminov <igor.perminov@inbox.ru>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2500usb.c

diff --git a/drivers/net/wireless/rt2x00/rt2500usb.c b/drivers/net/wireless/rt2x00/rt2500usb.c
index de48c5c..09a5894 100644
--- a/drivers/net/wireless/rt2x00/rt2500usb.c
+++ b/drivers/net/wireless/rt2x00/rt2500usb.c
@@ -1238,8 +1238,6 @@
 	 * otherwise we might be sending out invalid data.
 	 */
 	rt2500usb_register_read(rt2x00dev, TXRX_CSR19, &reg);
-	rt2x00_set_field16(&reg, TXRX_CSR19_TSF_COUNT, 0);
-	rt2x00_set_field16(&reg, TXRX_CSR19_TBCN, 0);
 	rt2x00_set_field16(&reg, TXRX_CSR19_BEACON_GEN, 0);
 	rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg);
 
@@ -1287,7 +1285,7 @@
 static void rt2500usb_kick_tx_queue(struct rt2x00_dev *rt2x00dev,
 				    const enum data_queue_qid queue)
 {
-	u16 reg;
+	u16 reg, reg0;
 
 	if (queue != QID_BEACON) {
 		rt2x00usb_kick_tx_queue(rt2x00dev, queue);
@@ -1298,16 +1296,19 @@
 	if (!rt2x00_get_field16(reg, TXRX_CSR19_BEACON_GEN)) {
 		rt2x00_set_field16(&reg, TXRX_CSR19_TSF_COUNT, 1);
 		rt2x00_set_field16(&reg, TXRX_CSR19_TBCN, 1);
+		reg0 = reg;
 		rt2x00_set_field16(&reg, TXRX_CSR19_BEACON_GEN, 1);
 		/*
 		 * Beacon generation will fail initially.
-		 * To prevent this we need to register the TXRX_CSR19
-		 * register several times.
+		 * To prevent this we need to change the TXRX_CSR19
+		 * register several times (reg0 is the same as reg
+		 * except for TXRX_CSR19_BEACON_GEN, which is 0 in reg0
+		 * and 1 in reg).
 		 */
 		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg);
-		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, 0);
+		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg0);
 		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg);
-		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, 0);
+		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg0);
 		rt2500usb_register_write(rt2x00dev, TXRX_CSR19, reg);
 	}
 }