[PATCH 4.9 147/271] serial: stm32: fix transmit_chars when tx is stopped

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Erwan Le Ray <erwan.leray@xxxxxx>

[ Upstream commit b83b957c91f68e53f0dc596e129e8305761f2a32 ]

Disables the tx irq  when the transmission is ended and updates stop_tx
conditions for code cleanup.

Fixes: 48a6092fb41f ("serial: stm32-usart: Add STM32 USART Driver")
Signed-off-by: Erwan Le Ray <erwan.leray@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/tty/serial/stm32-usart.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 033856287ca21..ea8b591dd46f4 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -293,13 +293,8 @@ static void stm32_transmit_chars(struct uart_port *port)
 		return;
 	}
 
-	if (uart_tx_stopped(port)) {
-		stm32_stop_tx(port);
-		return;
-	}
-
-	if (uart_circ_empty(xmit)) {
-		stm32_stop_tx(port);
+	if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
+		stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
 		return;
 	}
 
@@ -312,7 +307,7 @@ static void stm32_transmit_chars(struct uart_port *port)
 		uart_write_wakeup(port);
 
 	if (uart_circ_empty(xmit))
-		stm32_stop_tx(port);
+		stm32_clr_bits(port, ofs->cr1, USART_CR1_TXEIE);
 }
 
 static irqreturn_t stm32_interrupt(int irq, void *ptr)
-- 
2.20.1