arm: mvebu: clearfog: document eMMC installation

Document build and install of U-Boot image on Clearfog with eMMC.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Stefan Roese <sr@denx.de>

diff --git a/board/solidrun/clearfog/README b/board/solidrun/clearfog/README
index a7bc0d4..0b0e98d 100644 (file)
--- a/board/solidrun/clearfog/README
+++ b/board/solidrun/clearfog/README
@@ -17,6 +17,29 @@ $ sudo dd if=u-boot-spl.kwb of=/dev/sdX bs=512 seek=1
 Please use the correct device node for your setup instead
 of "/dev/sdX" here!
 
+Install U-Boot on eMMC:
+-----------------------
+
+The ROM loads the bootloader from eMMC first boot partition at offset 0. This
+is unlike load from SD card that is at offset 512. As a result, the offset of
+the main U-Boot image on the eMMC boot partition changes. Set
+CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR to 0x140 for SPL to load U-Boot from
+the correct location.
+
+To make SPL load the main U-Boot image from the eMMC boot partition enable
+eMMC boot acknowledgement and boot partition with the following U-Boot
+command:
+
+  mmc partconf 0 1 1 0
+
+Install U-Boot on eMMC boot partition from Linux running on Clearfog:
+
+  echo 0 > /sys/block/mmcblk0boot0/force_ro
+  dd if=u-boot-spl.kwb of=/dev/mmcblk0boot0
+
+Note that the SD card is not accessible when the Clearfog SOM has eMMC.
+Consider initial boot from UART (see below).
+
 Boot selection:
 ---------------