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>

1 files changed, 8 insertions, 7 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2500usb.c b/drivers/net/wireless/rt2x00/rt2500usb.c
index de48c5c68eff..09a589432dab 100644
--- a/drivers/net/wireless/rt2x00/rt2500usb.c
+++ b/drivers/net/wireless/rt2x00/rt2500usb.c
@@ -1238,8 +1238,6 @@ static void rt2500usb_write_beacon(struct queue_entry *entry)
          * 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 int rt2500usb_get_tx_data_len(struct queue_entry *entry)
 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 @@ static void rt2500usb_kick_tx_queue(struct rt2x00_dev *rt2x00dev,
         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);
         }
 }