[PATCH 09/14] tty/serial/amba-pl011: Implement clear_irqs callback

It's all pretty straightforward, except for TXIM interrupt. The interrupt
has meaning "ready to transmit", so it's almost always raised, and the
only way to silence it is to mask it. But that's OK, ops->start_tx will
unmask it.

Signed-off-by: Anton Vorontsov <redacted>
---
 drivers/tty/serial/amba-pl011.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 88e2df2..7522d97 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c

@@ -1308,6 +1308,18 @@ 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, this is "ready to transmit IRQ", so
+	 * we simply mask it. ops->start_tx will unmask it.
+	 */