mt76: mt76x02: remove irqsave/restore in locking for tx status fifo

Use a separate lock and spin_trylock to avoid disabling interrupts.
Should improve performance and latency
Signed-off-by: Felix Fietkau <nbd@nbd.name>

drivers/net/wireless/mediatek/mt76/mt76x02.h

@@ -86,6 +86,7 @@ struct mt76x02_dev {
 
 	u8 txdone_seq;
 	DECLARE_KFIFO_PTR(txstatus_fifo, struct mt76x02_tx_status);
+	spinlock_t txstatus_fifo_lock;
 
 	struct sk_buff *rx_head;
 

drivers/net/wireless/mediatek/mt76/mt76x02_mac.c

@@ -739,7 +739,6 @@ int mt76x02_mac_process_rx(struct mt76x02_dev *dev, struct sk_buff *skb,
 void mt76x02_mac_poll_tx_status(struct mt76x02_dev *dev, bool irq)
 {
 	struct mt76x02_tx_status stat = {};
-	unsigned long flags;
 	u8 update = 1;
 	bool ret;
 
@@ -749,9 +748,11 @@ void mt76x02_mac_poll_tx_status(struct mt76x02_dev *dev, bool irq)
 	trace_mac_txstat_poll(dev);
 
 	while (!irq || !kfifo_is_full(&dev->txstatus_fifo)) {
-		spin_lock_irqsave(&dev->mt76.mmio.irq_lock, flags);
+		if (!spin_trylock(&dev->txstatus_fifo_lock))
+			break;
+
 		ret = mt76x02_mac_load_tx_status(dev, &stat);
-		spin_unlock_irqrestore(&dev->mt76.mmio.irq_lock, flags);
+		spin_unlock(&dev->txstatus_fifo_lock);
 
 		if (!ret)
 			break;

drivers/net/wireless/mediatek/mt76/mt76x02_mmio.c

@@ -201,6 +201,7 @@ int mt76x02_dma_init(struct mt76x02_dev *dev)
 	tasklet_init(&dev->pre_tbtt_tasklet, mt76x02_pre_tbtt_tasklet,
 		     (unsigned long)dev);
 
+	spin_lock_init(&dev->txstatus_fifo_lock);
 	kfifo_init(&dev->txstatus_fifo, status_fifo, fifo_size);
 
 	mt76_dma_attach(&dev->mt76);