diff --git a/doc/README.mx31 b/doc/README.mx31
new file mode 100644
index 0000000..f912b66
--- /dev/null
+++ b/doc/README.mx31
@@ -0,0 +1,19 @@
+
+U-Boot for Freescale i.MX31
+
+This file contains information for the port of U-Boot to the Freescale
+i.MX31 SoC.
+
+1. CONFIGURATION OPTIONS/SETTINGS
+---------------------------------
+
+1.1 Configuration of MC13783 SPI bus
+------------------------------------
+The power management companion chip MC13783 is connected to the
+i.MX31 via an SPI bus. Use the following configuration options
+to setup the bus and chip select used for a particular board.
+
+CONFIG_MC13783_SPI_BUS	-- defines the SPI bus the MC13783 is connected to.
+			   Note that 0 is CSPI1, 1 is CSPI2 and 2 is CSPI3.
+CONFIG_MC13783_SPI_CS	-- define the chip select the MC13783 s connected to.
+
diff --git a/drivers/rtc/mc13783-rtc.c b/drivers/rtc/mc13783-rtc.c
index 6ea9137..05db2f1 100644
--- a/drivers/rtc/mc13783-rtc.c
+++ b/drivers/rtc/mc13783-rtc.c
@@ -34,7 +34,8 @@
 
 	if (!slave) {
 		/* FIXME: Verify the max SCK rate */
-		slave = spi_setup_slave(1, 0, 1000000,
+		slave = spi_setup_slave(CONFIG_MC13783_SPI_BUS,
+				CONFIG_MC13783_SPI_CS, 1000000,
 				SPI_MODE_2 | SPI_CS_HIGH);
 		if (!slave)
 			return -1;
@@ -83,7 +84,8 @@
 
 	if (!slave) {
 		/* FIXME: Verify the max SCK rate */
-		slave = spi_setup_slave(1, 0, 1000000,
+		slave = spi_setup_slave(CONFIG_MC13783_SPI_BUS,
+				CONFIG_MC13783_SPI_CS, 1000000,
 				SPI_MODE_2 | SPI_CS_HIGH);
 		if (!slave)
 			return -1;
diff --git a/include/configs/imx31_litekit.h b/include/configs/imx31_litekit.h
index c476333..62a03fa 100644
--- a/include/configs/imx31_litekit.h
+++ b/include/configs/imx31_litekit.h
@@ -69,6 +69,9 @@
 #define CONFIG_DEFAULT_SPI_MODE	(SPI_MODE_2 | SPI_CS_HIGH)
 
 #define CONFIG_RTC_MC13783	1
+/* MC13783 connected to CSPI2 and SS0 */
+#define CONFIG_MC13783_SPI_BUS	1
+#define CONFIG_MC13783_SPI_CS	0
 
 /* allow to overwrite serial and ethaddr */
 #define CONFIG_ENV_OVERWRITE
diff --git a/include/configs/mx31ads.h b/include/configs/mx31ads.h
index 9ede764..b9ad3e4 100644
--- a/include/configs/mx31ads.h
+++ b/include/configs/mx31ads.h
@@ -66,6 +66,9 @@
 #define CONFIG_DEFAULT_SPI_MODE	(SPI_MODE_2 | SPI_CS_HIGH)
 
 #define CONFIG_RTC_MC13783	1
+/* MC13783 connected to CSPI2 and SS0 */
+#define CONFIG_MC13783_SPI_BUS	1
+#define CONFIG_MC13783_SPI_CS	0
 
 /* allow to overwrite serial and ethaddr */
 #define CONFIG_ENV_OVERWRITE