serial: sh-sci: Don't overwrite clock selection in serial_console_write()

Blindly writing the default configuration value into the SCSCR register
may change the clock selection bits, breaking the serial console if the
current driver settings differ from the default settings.

Keep the current clock selection bits to prevent this from happening
on e.g. r8a7791/koelsch when support for the BRG will be added.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 05ac153..136ad2f 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2420,7 +2420,7 @@ static void serial_console_write(struct console *co, const char *s,
 {
        struct sci_port *sci_port = &sci_ports[co->index];
        struct uart_port *port = &sci_port->port;
-       unsigned short bits, ctrl;
+       unsigned short bits, ctrl, ctrl_temp;
        unsigned long flags;
        int locked = 1;
 
@@ -2432,9 +2432,11 @@ static void serial_console_write(struct console *co, const char *s,
        else
                spin_lock(&port->lock);
 
-       /* first save the SCSCR then disable the interrupts */
+       /* first save SCSCR then disable interrupts, keep clock source */
        ctrl = serial_port_in(port, SCSCR);
-       serial_port_out(port, SCSCR, sci_port->cfg->scscr);
+       ctrl_temp = (sci_port->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0)) |
+                   (ctrl & (SCSCR_CKE1 | SCSCR_CKE0));
+       serial_port_out(port, SCSCR, ctrl_temp);
 
        uart_console_write(port, s, count, serial_console_putchar);