serial: sh-sci: earlyprintk zero uartclk fix

This establishes a sensible max baud rate for the earlyprintk cases where
the port's uartclk has not yet been determined.
Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/serial/sh-sci.c

@@ -897,11 +897,21 @@ static void sci_shutdown(struct uart_port *port)
 static void sci_set_termios(struct uart_port *port, struct ktermios *termios,
 			    struct ktermios *old)
 {
-	unsigned int status, baud, smr_val;
+	unsigned int status, baud, smr_val, max_baud;
 	int t = -1;
 
-	baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
-	if (likely(baud))
+	/*
+	 * earlyprintk comes here early on with port->uartclk set to zero.
+	 * the clock framework is not up and running at this point so here
+	 * we assume that 115200 is the maximum baud rate. please note that
+	 * the baud rate is not programmed during earlyprintk - it is assumed
+	 * that the previous boot loader has enabled required clocks and
+	 * setup the baud rate generator hardware for us already.
+	 */
+	max_baud = port->uartclk ? port->uartclk / 16 : 115200;
+
+	baud = uart_get_baud_rate(port, termios, old, 0, max_baud);
+	if (likely(baud && port->uartclk))
 		t = SCBRR_VALUE(baud, port->uartclk);
 
 	do {