[PATCH 3/3] mt76: mt7663s: fix the deadlock caused by sdio->stat_work

[sean.wang at mediatek.com]

From: Sean Wang <sean.wang at mediatek.com>

Because wake_work and sdio->stat_work share the same workqueue mt76->wq,
if sdio->stat_work cannot acquire the mutex lock such as that was possibly
held up by mt7615_mutex_acquire, we should exit immediately and schedule
another stat_work to avoid blocking the mt7615_mutex_acquire.

Also, if mt7615_mutex_acquire was called by sdio->stat_work self, the wake
would be blocked by itself, so we have to changing into an unblocking wake
(directly wakeup via mt7615_mcu_drv_pmctrl, not via the wake_work) in the
context.

Fixes: a66cbdd6573d ("mt76: mt7615: introduce mt7663s support")
Co-developed-by: YN Chen <YN.Chen at mediatek.com>
Signed-off-by: YN Chen <YN.Chen at mediatek.com>
Signed-off-by: Sean Wang <sean.wang at mediatek.com>
---
 .../wireless/mediatek/mt76/mt7615/usb_sdio.c  | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/mt7615/usb_sdio.c b/drivers/net/wireless/mediatek/mt76/mt7615/usb_sdio.c
index 0052d103e276..5991b23e0d13 100644
--- a/drivers/net/wireless/mediatek/mt76/mt7615/usb_sdio.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7615/usb_sdio.c
@@ -157,10 +157,29 @@ bool mt7663_usb_sdio_tx_status_data(struct mt76_dev *mdev, u8 *update)
 {
 	struct mt7615_dev *dev = container_of(mdev, struct mt7615_dev, mt76);
 
-	mt7615_mutex_acquire(dev);
+	if (!mutex_trylock(&mdev->mutex)) {
+		/* Because wake_work and stat_work share the same workqueue
+		 * mt76->wq, if sdio->stat_work cannot acquire the mutex lock,
+		 * we should exit immediately and schedule another stat_work
+		 * to avoid blocking the wake_work.
+		 */
+		struct work_struct *stat_work;
+
+		stat_work = mt76_is_sdio(mdev) ? &mdev->sdio.stat_work :
+			    &mdev->usb.stat_work;
+		queue_work(dev->mt76.wq, stat_work);
+
+		goto out;
+	}
+
+	mt7615_mcu_set_drv_ctrl(dev);
+
 	mt7615_mac_sta_poll(dev);
-	mt7615_mutex_release(dev);
 
+	mt76_connac_power_save_sched(&mdev->phy, &dev->pm);
+	mutex_unlock(&mdev->mutex);
+
+out:
 	return false;
 }
 EXPORT_SYMBOL_GPL(mt7663_usb_sdio_tx_status_data);
-- 
2.25.1