[PATCH 3/3] serial: qcom-geni: fix garbage output after buffer flush

[Johan Hovold <johan+linaro@kernel.org>]

The Qualcomm GENI serial driver does not handle buffer flushing and
outputs garbage (or NUL) characters for the remainder of any active TX
command after the write buffer has been cleared.

Implement the flush_buffer() callback and use it to cancel any active TX
command when the write buffer has been emptied.

Fixes: a1fee899e5be ("tty: serial: qcom_geni_serial: Fix softlock")
Cc: stable@vger.kernel.org	# 5.0
Reported-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
---
 drivers/tty/serial/qcom_geni_serial.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c
index 72addeb9f461..5fbb72f1c0c7 100644
--- a/drivers/tty/serial/qcom_geni_serial.c
+++ b/drivers/tty/serial/qcom_geni_serial.c
@@ -1084,6 +1084,11 @@ static void qcom_geni_serial_shutdown(struct uart_port *uport)
 	qcom_geni_serial_clear_tx_fifo(uport);
 }
 
+static void qcom_geni_serial_flush_buffer(struct uart_port *uport)
+{
+	qcom_geni_serial_clear_tx_fifo(uport);
+}
+
 static int qcom_geni_serial_port_setup(struct uart_port *uport)
 {
 	struct qcom_geni_serial_port *port = to_dev_port(uport);
@@ -1540,6 +1545,7 @@ static const struct uart_ops qcom_geni_console_pops = {
 	.request_port = qcom_geni_serial_request_port,
 	.config_port = qcom_geni_serial_config_port,
 	.shutdown = qcom_geni_serial_shutdown,
+	.flush_buffer = qcom_geni_serial_flush_buffer,
 	.type = qcom_geni_serial_get_type,
 	.set_mctrl = qcom_geni_serial_set_mctrl,
 	.get_mctrl = qcom_geni_serial_get_mctrl,
-- 
2.44.1