mt76: mt7921s: fix the deadlock caused by sdio->stat_work

Quoted 7 lines

Quoted 1 line

From: Sean Wang <[email protected]>

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 mt7921_mutex_acquire, we should exit immediately and schedule another stat_work to avoid blocking the mt7921_mutex_acquire.

Quoted 4 lines

Also, if mt7921_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 mt7921_mcu_drv_pmctrl, not via the wake_work) in the context.

Hi Sean,

it seems to me we are missing some logic here (e.g cancelling ps_work as we do in mt76_connac_pm_wake()). Is it enough to move mt7921_usb_sdio_tx_status_data on mac80211 workqueue? Can you see any performance issue? (same for mt7663).

Regards,
Lorenzo

Quoted 49 lines

Fixes 48fab5bbef40 ("mt76: mt7921: introduce mt7921s support")

Co-developed-by YN Chen <[email protected]>

Signed-off-by YN Chen <[email protected]>

Signed-off-by Sean Wang <[email protected]>

---
 .../net/wireless/mediatek/mt76/mt7921/mac.c   | 22 +++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

drivers/net/wireless/mediatek/mt76/mt7921/mac.c +20 -2

index 6bd9fc9228a2..75e719175e92 100644
@@ -1080,10 +1080,28 @@ bool mt7921_usb_sdio_tx_status_data(struct
 mt76_dev *mdev, u8 *update)  {
 	struct mt7921_dev *dev = container_of(mdev, struct mt7921_dev,
 mt76);
 
-	mt7921_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;
+	}
+
+	mt7921_mcu_drv_pmctrl(dev);
 	mt7921_mac_sta_poll(dev);
-	mt7921_mutex_release(dev);
+	mt76_connac_power_save_sched(&mdev->phy, &dev->pm);
 
+	mutex_unlock(&mdev->mutex);
+
+out:
 	return false;
 }

EXPORT_SYMBOL_GPL(mt7921_usb_sdio_tx_status_data);
--
2.25.1