diff --git a/drivers/char/rtc.c b/drivers/char/rtc.c
index a162e1b3d5d3..0c66b802736a 100644
--- a/drivers/char/rtc.c
+++ b/drivers/char/rtc.c
@@ -918,12 +918,29 @@ static const struct file_operations rtc_proc_fops = {
 };
 #endif
 
+static resource_size_t rtc_size;
+
+static struct resource * __init rtc_request_region(resource_size_t size)
+{
+	struct resource *r;
+
+	if (RTC_IOMAPPED)
+		r = request_region(RTC_PORT(0), size, "rtc");
+	else
+		r = request_mem_region(RTC_PORT(0), size, "rtc");
+
+	if (r)
+		rtc_size = size;
+
+	return r;
+}
+
 static void rtc_release_region(void)
 {
 	if (RTC_IOMAPPED)
-		release_region(RTC_PORT(0), RTC_IO_EXTENT);
+		release_region(RTC_PORT(0), rtc_size);
 	else
-		release_mem_region(RTC_PORT(0), RTC_IO_EXTENT);
+		release_mem_region(RTC_PORT(0), rtc_size);
 }
 
 static int __init rtc_init(void)
@@ -976,10 +993,17 @@ static int __init rtc_init(void)
 	}
 no_irq:
 #else
-	if (RTC_IOMAPPED)
-		r = request_region(RTC_PORT(0), RTC_IO_EXTENT, "rtc");
-	else
-		r = request_mem_region(RTC_PORT(0), RTC_IO_EXTENT, "rtc");
+	r = rtc_request_region(RTC_IO_EXTENT);
+
+	/*
+	 * If we've already requested a smaller range (for example, because
+	 * PNPBIOS or ACPI told us how the device is configured), the request
+	 * above might fail because it's too big.
+	 *
+	 * If so, request just the range we actually use.
+	 */
+	if (!r)
+		r = rtc_request_region(RTC_IO_EXTENT_USED);
 	if (!r) {
 #ifdef RTC_IRQ
 		rtc_has_irq = 0;
diff --git a/include/linux/mc146818rtc.h b/include/linux/mc146818rtc.h
index 580b3f4956ee..2f4e957af656 100644
--- a/include/linux/mc146818rtc.h
+++ b/include/linux/mc146818rtc.h
@@ -109,8 +109,11 @@ struct cmos_rtc_board_info {
 #ifndef ARCH_RTC_LOCATION	/* Override by <asm/mc146818rtc.h>? */
 
 #define RTC_IO_EXTENT	0x8
+#define RTC_IO_EXTENT_USED	0x2
 #define RTC_IOMAPPED	1	/* Default to I/O mapping. */
 
+#else
+#define RTC_IO_EXTENT_USED      RTC_IO_EXTENT
 #endif /* ARCH_RTC_LOCATION */
 
 #endif /* _MC146818RTC_H */