wlcore: Use spin_trylock in wlcore_irq() to see if we need to queue tx

We currently have a collection of flags and locking between the
threaded irq and tx work:

- wl->flags bitops
- wl->mutex
- wl->wl_lock spinlock

The bitops flags do not need a spinlock around them, and we only need
the spinlock to see if we need to queue tx work or not. And wlcore_irq()
holds the mutex.

To simplify the locking, we can use spin_trylock and always queue tx
work unless we know there's nothing to do.

Let's also update the comment a bit while at it.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200702162951.45392-4-tony@atomide.com

drivers/net/wireless/ti/wlcore/main.c

@@ -652,6 +652,7 @@ static irqreturn_t wlcore_irq(int irq, void *cookie)
 	int ret;
 	unsigned long flags;
 	struct wl1271 *wl = cookie;
+	bool queue_tx_work = true;
 
 	set_bit(WL1271_FLAG_IRQ_RUNNING, &wl->flags);
 
@@ -684,13 +685,17 @@ static irqreturn_t wlcore_irq(int irq, void *cookie)
 	if (ret)
 		wl12xx_queue_recovery_work(wl);
 
-	spin_lock_irqsave(&wl->wl_lock, flags);
-	/* In case TX was not handled here, queue TX work */
+	/* In case TX was not handled in wlcore_irq_locked(), queue TX work */
 	clear_bit(WL1271_FLAG_TX_PENDING, &wl->flags);
-	if (!test_bit(WL1271_FLAG_FW_TX_BUSY, &wl->flags) &&
-	    wl1271_tx_total_queue_count(wl) > 0)
-		ieee80211_queue_work(wl->hw, &wl->tx_work);
-	spin_unlock_irqrestore(&wl->wl_lock, flags);
+	if (!test_bit(WL1271_FLAG_FW_TX_BUSY, &wl->flags)) {
+		if (spin_trylock_irqsave(&wl->wl_lock, flags)) {
+			if (!wl1271_tx_total_queue_count(wl))
+				queue_tx_work = false;
+			spin_unlock_irqrestore(&wl->wl_lock, flags);
+		}
+		if (queue_tx_work)
+			ieee80211_queue_work(wl->hw, &wl->tx_work);
+	}
 
 	mutex_unlock(&wl->mutex);