imx: serial: use tty_encode_baud_rate to set true rate

real baud rate may be different from the one requested.
for upper layers, set the nearest value to the real rate
in favour of the rate previously requested.
Signed-off-by: Oskar Schirmer <os@emlix.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/serial/imx.c

@@ -818,6 +818,7 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 	unsigned int old_csize = old ? old->c_cflag & CSIZE : CS8;
 	unsigned int div, ufcr;
 	unsigned long num, denom;
+	uint64_t tdiv64;
 
 	/*
 	 * If we don't support modem control lines, don't allow
@@ -930,6 +931,12 @@ imx_set_termios(struct uart_port *port, struct ktermios *termios,
 	rational_best_approximation(16 * div * baud, sport->port.uartclk,
 		1 << 16, 1 << 16, &num, &denom);
 
+	tdiv64 = sport->port.uartclk;
+	tdiv64 *= num;
+	do_div(tdiv64, denom * 16 * div);
+	tty_encode_baud_rate(sport->port.info->port.tty,
+		(speed_t)tdiv64, (speed_t)tdiv64);
+
 	num -= 1;
 	denom -= 1;