diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 1468ec5047cc..95772cf4e7b0 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -84,7 +84,7 @@ struct sci_port {
 	int			overrun_bit;
 	unsigned int		error_mask;
 	unsigned int		sampling_rate;
-
+	resource_size_t		reg_size;
 
 	/* Break timer */
 	struct timer_list	break_timer;
@@ -2073,23 +2073,9 @@ static const char *sci_type(struct uart_port *port)
 	return NULL;
 }
 
-static inline unsigned long sci_port_size(struct uart_port *port)
-{
-	/*
-	 * Pick an arbitrary size that encapsulates all of the base
-	 * registers by default. This can be optimized later, or derived
-	 * from platform resource data at such a time that ports begin to
-	 * behave more erratically.
-	 */
-	if (port->type == PORT_HSCIF)
-		return 96;
-	else
-		return 64;
-}
-
 static int sci_remap_port(struct uart_port *port)
 {
-	unsigned long size = sci_port_size(port);
+	struct sci_port *sport = to_sci_port(port);
 
 	/*
 	 * Nothing to do if there's already an established membase.
@@ -2098,7 +2084,7 @@ static int sci_remap_port(struct uart_port *port)
 		return 0;
 
 	if (port->flags & UPF_IOREMAP) {
-		port->membase = ioremap_nocache(port->mapbase, size);
+		port->membase = ioremap_nocache(port->mapbase, sport->reg_size);
 		if (unlikely(!port->membase)) {
 			dev_err(port->dev, "can't remap port#%d\n", port->line);
 			return -ENXIO;
@@ -2117,23 +2103,28 @@ static int sci_remap_port(struct uart_port *port)
 
 static void sci_release_port(struct uart_port *port)
 {
+	struct sci_port *sport = to_sci_port(port);
+
 	if (port->flags & UPF_IOREMAP) {
 		iounmap(port->membase);
 		port->membase = NULL;
 	}
 
-	release_mem_region(port->mapbase, sci_port_size(port));
+	release_mem_region(port->mapbase, sport->reg_size);
 }
 
 static int sci_request_port(struct uart_port *port)
 {
-	unsigned long size = sci_port_size(port);
 	struct resource *res;
+	struct sci_port *sport = to_sci_port(port);
 	int ret;
 
-	res = request_mem_region(port->mapbase, size, dev_name(port->dev));
-	if (unlikely(res == NULL))
+	res = request_mem_region(port->mapbase, sport->reg_size,
+				 dev_name(port->dev));
+	if (unlikely(res == NULL)) {
+		dev_err(port->dev, "request_mem_region failed.");
 		return -EBUSY;
+	}
 
 	ret = sci_remap_port(port);
 	if (unlikely(ret != 0)) {
@@ -2207,6 +2198,7 @@ static int sci_init_single(struct platform_device *dev,
 		return -ENOMEM;
 
 	port->mapbase = res->start;
+	sci_port->reg_size = resource_size(res);
 
 	for (i = 0; i < ARRAY_SIZE(sci_port->irqs); ++i)
 		sci_port->irqs[i] = platform_get_irq(dev, i);