[PATCH 5.4 405/434] serial: sprd: Add clearing break interrupt operation

[Greg Kroah-Hartman]

From: Yonghan Ye <yonghan.ye@xxxxxxxxxx>

commit abeb2e9414d7e3a0d8417bc3b13d7172513ea8a0 upstream.

A break interrupt will be generated if the RX line was pulled low, which
means some abnomal behaviors occurred of the UART. In this case, we still
need to clear this break interrupt status, otherwise it will cause irq
storm to crash the whole system.

Fixes: b7396a38fb28 ("tty/serial: Add Spreadtrum sc9836-uart driver support")
Signed-off-by: Yonghan Ye <yonghan.ye@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Baolin Wang <baolin.wang7@xxxxxxxxx>
Link: https://lore.kernel.org/r/925e51b73099c90158e080b8f5bed9b3b38c4548.1575460601.git.baolin.wang7@xxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/tty/serial/sprd_serial.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/tty/serial/sprd_serial.c
+++ b/drivers/tty/serial/sprd_serial.c
@@ -679,6 +679,9 @@ static irqreturn_t sprd_handle_irq(int i
 	if (ims & SPRD_IMSR_TIMEOUT)
 		serial_out(port, SPRD_ICLR, SPRD_ICLR_TIMEOUT);
 
+	if (ims & SPRD_IMSR_BREAK_DETECT)
+		serial_out(port, SPRD_ICLR, SPRD_IMSR_BREAK_DETECT);
+
 	if (ims & (SPRD_IMSR_RX_FIFO_FULL | SPRD_IMSR_BREAK_DETECT |
 		   SPRD_IMSR_TIMEOUT))
 		sprd_rx(port);