thunderbolt: Handle ring interrupt by reading interrupt status register

As per USB4 specification by default "Disable ISR Auto-Clear" bit is set
to zero and the Tx/Rx ring interrupt status needs to be cleared.

Hence handle it by reading the interrupt status register (ISR) in the
MSI-X handler.
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Signed-off-by: Sanjay R Mehta <sanju.mehta@amd.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/nhi.c

@@ -382,11 +382,24 @@ void tb_ring_poll_complete(struct tb_ring *ring)
 }
 EXPORT_SYMBOL_GPL(tb_ring_poll_complete);
 
+static void ring_clear_msix(const struct tb_ring *ring)
+{
+	if (ring->nhi->quirks & QUIRK_AUTO_CLEAR_INT)
+		return;
+
+	if (ring->is_tx)
+		ioread32(ring->nhi->iobase + REG_RING_NOTIFY_BASE);
+	else
+		ioread32(ring->nhi->iobase + REG_RING_NOTIFY_BASE +
+			 4 * (ring->nhi->hop_count / 32));
+}
+
 static irqreturn_t ring_msix(int irq, void *data)
 {
 	struct tb_ring *ring = data;
 
 	spin_lock(&ring->nhi->lock);
+	ring_clear_msix(ring);
 	spin_lock(&ring->lock);
 	__ring_interrupt(ring);
 	spin_unlock(&ring->lock);