tty/serial: atmel: fix out of range clock divider handling

BugLink: https://bugs.launchpad.net/bugs/1860602
[ Upstream commit cb47b9f8630ae3fa3f5fbd0c7003faba7abdf711 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
index a200c4ec7c433647ce2ee52418865a5ffc764e4b..ef187bcb65afe91c02ebce4655dac715e58f61f3 100644 (file)
--- a/drivers/tty/serial/atmel_serial.c
+++ b/drivers/tty/serial/atmel_serial.c
@@ -2154,27 +2154,6 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
                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
@@ -2200,6 +2179,28 @@ static void atmel_set_termios(struct uart_port *port, struct ktermios *termios,
        quot = cd | fp << ATMEL_US_FP_OFFSET;
 
        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;