staging: vt6656: implement power saving code.

The device should ready to listen to next beacon so on count down of
wake_up_count == 1.

schedule command WLAN_CMD_TBTT_WAKEUP which calls vnt_next_tbtt_wakeup which
wakes the device.

This restores this back to vendors code with a slight difference the
count down is in the interrupt handler.
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vt6656/device.h

@@ -389,6 +389,8 @@ struct vnt_private {
 	u8 bb_pre_ed_rssi;
 	u8 bb_pre_ed_index;
 
+	u16 wake_up_count;
+
 	/* command timer */
 	struct delayed_work run_command_work;
 

drivers/staging/vt6656/int.c

@@ -149,10 +149,18 @@ void vnt_int_process_data(struct vnt_private *priv)
 				priv->op_mode == NL80211_IFTYPE_AP)
 			vnt_schedule_command(priv, WLAN_CMD_BECON_SEND);
 
-		if (int_data->isr0 & ISR_TBTT) {
-			if (priv->hw->conf.flags & IEEE80211_CONF_PS)
+		if (int_data->isr0 & ISR_TBTT &&
+		    priv->hw->conf.flags & IEEE80211_CONF_PS) {
+			if (!priv->wake_up_count)
+				priv->wake_up_count =
+					priv->hw->conf.listen_interval;
+
+			--priv->wake_up_count;
+
+			/* Turn on wake up to listen next beacon */
+			if (priv->wake_up_count == 1)
 				vnt_schedule_command(priv,
-							WLAN_CMD_TBTT_WAKEUP);
+						     WLAN_CMD_TBTT_WAKEUP);
 		}
 		priv->current_tsf = le64_to_cpu(int_data->tsf);
 

drivers/staging/vt6656/power.c

@@ -134,7 +134,7 @@ int vnt_next_tbtt_wakeup(struct vnt_private *priv)
 	struct ieee80211_conf *conf = &hw->conf;
 	int wake_up = false;
 
-	if (conf->listen_interval == 1) {
+	if (conf->listen_interval > 1) {
 		/* Turn on wake up to listen next beacon */
 		vnt_mac_reg_bits_on(priv, MAC_REG_PSCTL, PSCTL_LNBCN);
 		wake_up = true;