[PATCH 07/12] tty/serial/amba-pl011: Implement clear_irqs callback

@@ -1307,6 +1307,27 @@ static void pl011_put_poll_char(struct uart_port *port,
 	writew(ch, uap->port.membase + UART01x_DR);
 }
 
+static void pl011_clear_irqs(struct uart_port *port)
+{
+	struct uart_amba_port *uap = (struct uart_amba_port *)port;
+	unsigned char __iomem *regs = uap->port.membase;
+
+	writew(readw(regs + UART011_MIS), regs + UART011_ICR);
+	/*
+	 * There is no way to clear TXIM as this is "ready to transmit IRQ", so
+	 * we simply mask it. start_tx() will unmask it.
+	 *
+	 * Note we can race with start_tx(), and if the race happens, the
+	 * clear_irq() caller might get another interrupt just after we clear
+	 * it.  But it should be OK and can happen even w/o the race, e.g.
+	 * controller immediately got some new data and raised the IRQ.
+	 *
+	 * And whoever calls clear_irqs() assumes that the caller manages the
+	 * device (including tx queue), so we're also fine with start_tx()'s
+	 * caller side.
+	 */
+	writew(readw(regs + UART011_IMSC) & ~UART011_TXIM, regs + UART011_IMSC);
+}
 #endif /* CONFIG_CONSOLE_POLL */
 
 static int pl011_hwinit(struct uart_port *port)

@@ -1712,6 +1733,7 @@ static struct uart_ops amba_pl011_pops = {
 	.poll_init     = pl011_hwinit,
 	.poll_get_char = pl011_get_poll_char,
 	.poll_put_char = pl011_put_poll_char,
+	.clear_irqs    = pl011_clear_irqs,
 #endif
 };