rt2x00: add mutex to synchronize config and link tuner

Do not perform mac80211 config and link_tuner at the same time,
this can possibly result in wrong RF or BBP configuration.
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/ralink/rt2x00/rt2x00.h

@@ -833,6 +833,10 @@ struct rt2x00_dev {
 	 */
 	struct mutex csr_mutex;
 
+	/*
+	 * Mutex to synchronize config and link tuner.
+	 */
+	struct mutex conf_mutex;
 	/*
 	 * Current packet filter configuration for the device.
 	 * This contains all currently active FIF_* flags send

drivers/net/wireless/ralink/rt2x00/rt2x00dev.c

@@ -1313,6 +1313,7 @@ int rt2x00lib_probe_dev(struct rt2x00_dev *rt2x00dev)
 
 	spin_lock_init(&rt2x00dev->irqmask_lock);
 	mutex_init(&rt2x00dev->csr_mutex);
+	mutex_init(&rt2x00dev->conf_mutex);
 	INIT_LIST_HEAD(&rt2x00dev->bar_list);
 	spin_lock_init(&rt2x00dev->bar_list_lock);
 

drivers/net/wireless/ralink/rt2x00/rt2x00link.c

@@ -363,6 +363,9 @@ static void rt2x00link_tuner(struct work_struct *work)
 	    test_bit(DEVICE_STATE_SCANNING, &rt2x00dev->flags))
 		return;
 
+	/* Do not race with rt2x00mac_config(). */
+	mutex_lock(&rt2x00dev->conf_mutex);
+
 	if (rt2x00dev->intf_sta_count)
 		rt2x00link_tuner_sta(rt2x00dev, link);
 
@@ -375,6 +378,8 @@ static void rt2x00link_tuner(struct work_struct *work)
 	    (link->count % (VCO_SECONDS / LINK_TUNE_SECONDS)) == 0)
 		rt2x00dev->ops->lib->vco_calibration(rt2x00dev);
 
+	mutex_unlock(&rt2x00dev->conf_mutex);
+
 	/*
 	 * Increase tuner counter, and reschedule the next link tuner run.
 	 */

drivers/net/wireless/ralink/rt2x00/rt2x00mac.c

@@ -320,6 +320,9 @@ int rt2x00mac_config(struct ieee80211_hw *hw, u32 changed)
 	 */
 	rt2x00queue_stop_queue(rt2x00dev->rx);
 
+	/* Do not race with with link tuner. */
+	mutex_lock(&rt2x00dev->conf_mutex);
+
 	/*
 	 * When we've just turned on the radio, we want to reprogram
 	 * everything to ensure a consistent state
@@ -335,6 +338,8 @@ int rt2x00mac_config(struct ieee80211_hw *hw, u32 changed)
 	 */
 	rt2x00lib_config_antenna(rt2x00dev, rt2x00dev->default_ant);
 
+	mutex_unlock(&rt2x00dev->conf_mutex);
+
 	/* Turn RX back on */
 	rt2x00queue_start_queue(rt2x00dev->rx);