mx6sabreauto: Add Falcon mode support

Add support for Falcon mode and explain in the README the steps to
boot the kernel directly without loading the full U-Boot.

Signed-off-by: Diego Dorta <diego.dorta@nxp.com>
Acked-by: Fabio Estevam <fabio.estevam@nxp.com>

2 files changed, 69 insertions, 0 deletions

diff --git a/board/freescale/mx6sabreauto/README b/board/freescale/mx6sabreauto/README
index 7e4596ad75..e8c589b92a 100644
--- a/board/freescale/mx6sabreauto/README
+++ b/board/freescale/mx6sabreauto/README
@@ -18,3 +18,65 @@ $ sudo dd if=SPL of=/dev/sdX bs=1K seek=1 && sync
 - Flash the u-boot.img binary into the SD card:
 
 $ sudo dd if=u-boot.img of=/dev/sdX bs=1K seek=69 && sync
+
+Booting via Falcon mode
+-----------------------
+
+Write in mx6sabreauto_defconfig the following define below:
+
+CONFIG_SPL_OS_BOOT=y
+
+In order to build it:
+
+$ make mx6sabreauto_defconfig
+
+$ make
+
+This will generate the SPL image called SPL and the u-boot.img.
+
+- Flash the SPL image into the SD card:
+
+$ sudo dd if=SPL of=/dev/sdb bs=1K seek=1 && sync
+
+- Flash the u-boot.img image into the SD card:
+
+$ sudo dd if=u-boot.img of=/dev/sdb bs=1K seek=69 && sync
+
+Create a FAT16 boot partition to store uImage and the dtb file, then copy the files there:
+
+$ sudo cp uImage /media/boot
+
+$ sudo cp imx6dl-sabreauto.dtb /media/boot
+
+Create a partition for root file system and extract it there:
+
+$ sudo tar xvf rootfs.tar.gz -C /media/root
+
+The SD card must have enough space for raw "args" and "kernel".
+To configure Falcon mode for the first time, on U-Boot do the following commands:
+
+- Load dtb file from boot partition:
+
+# load mmc 0:1 ${fdt_addr} imx6dl-sabreauto.dtb
+
+- Load kernel image from boot partition:
+
+# load mmc 0:1 ${loadaddr} uImage
+
+- Write kernel at 2MB offset:
+
+# mmc write ${loadaddr} 0x1000 0x4000
+
+- Setup kernel bootargs:
+
+# setenv bootargs "console=ttymxc3,115200 root=/dev/mmcblk0p1 rootfstype=ext4 rootwait quiet rw"
+
+- Prepare args:
+
+# spl export fdt ${loadaddr} - ${fdt_addr}
+
+- Write args 1MB data (0x800 sectors) to 1MB offset (0x800 sectors)
+
+# mmc write 18000000 0x800 0x800
+
+- Restart the board and then SPL binary will launch the kernel directly.
diff --git a/board/freescale/mx6sabreauto/mx6sabreauto.c b/board/freescale/mx6sabreauto/mx6sabreauto.c
index bfd5ffa5c7..a8fe251134 100644
--- a/board/freescale/mx6sabreauto/mx6sabreauto.c
+++ b/board/freescale/mx6sabreauto/mx6sabreauto.c
@@ -745,6 +745,13 @@ int board_ehci_power(int port, int on)
 #include <spl.h>
 #include <libfdt.h>
 
+#ifdef CONFIG_SPL_OS_BOOT
+int spl_start_uboot(void)
+{
+	return 0;
+}
+#endif
+
 static void ccgr_init(void)
 {
 	struct mxc_ccm_reg *ccm = (struct mxc_ccm_reg *)CCM_BASE_ADDR;