[PATCH 5.4 404/434] tty/serial: atmel: fix out of range clock divider handling

Greg Kroah-Hartman
2019-12-29T17:57:37Z

From: David Engraf <david.engraf@sysgo.com>

commit cb47b9f8630ae3fa3f5fbd0c7003faba7abdf711 upstream.

Use MCK_DIV8 when the clock divider is > 65535. Unfortunately the mode
register was already written thus the clock selection is ignored.

Fix by doing the baud rate calulation before setting the mode.

Fixes: 5bf5635ac170 ("tty/serial: atmel: add fractional baud rate support")
Signed-off-by: David Engraf <david.engraf@sysgo.com>
Acked-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Acked-by: Richard Genoud <richard.genoud@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191216085403.17050-1-david.engraf@sysgo.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/tty/serial/atmel_serial.c | 43 +++++++++++++++++++-------------------
1 file changed, 22 insertions(+), 21 deletions(-)

--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2270,27 +2270,6 @@ static void atmel_set_termios(struct uar
mode |= ATMEL_US_USMODE_NORMAL;
}

- /* set the mode, clock divisor, parity, stop bits and data size */
- atmel_uart_writel(port, ATMEL_US_MR, mode);
-
- /*
- * when switching the mode, set the RTS line state according to the
- * new mode, otherwise keep the former state
- */
- if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) {
- unsigned int rts_state;
-
- if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
- /* let the hardware control the RTS line */
- rts_state = ATMEL_US_RTSDIS;
- } else {
- /* force RTS line to low level */
- rts_state = ATMEL_US_RTSEN;
- }
-
- atmel_uart_writel(port, ATMEL_US_CR, rts_state);
- }
-
/*
* Set the baud rate:
* Fractional baudrate allows to setup output frequency more
@@ -2317,6 +2296,28 @@ static void atmel_set_termios(struct uar

if (!(port->iso7816.flags & SER_ISO7816_ENABLED))
atmel_uart_writel(port, ATMEL_US_BRGR, quot);
+
+ /* set the mode, clock divisor, parity, stop bits and data size */
+ atmel_uart_writel(port, ATMEL_US_MR, mode);
+
+ /*
+ * when switching the mode, set the RTS line state according to the
+ * new mode, otherwise keep the former state
+ */
+ if ((old_mode & ATMEL_US_USMODE) != (mode & ATMEL_US_USMODE)) {
+ unsigned int rts_state;
+
+ if ((mode & ATMEL_US_USMODE) == ATMEL_US_USMODE_HWHS) {
+ /* let the hardware control the RTS line */
+ rts_state = ATMEL_US_RTSDIS;
+ } else {
+ /* force RTS line to low level */
+ rts_state = ATMEL_US_RTSEN;
+ }
+
+ atmel_uart_writel(port, ATMEL_US_CR, rts_state);
+ }
+
atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_RSTSTA | ATMEL_US_RSTRX);
atmel_uart_writel(port, ATMEL_US_CR, ATMEL_US_TXEN | ATMEL_US_RXEN);
atmel_port->tx_stopped = false;