configs/kontron_smarc_sal28: enable u-boot

Enable building of the bootloader and integrate it into the resulting
image.

Signed-off-by: Michael Walle <michael@walle.cc>
Tested-by: Heiko Thiery <heiko.thiery@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

board/kontron/smarc-sal28/genimage.cfg

@@ -3,6 +3,12 @@ image sdcard-emmc.img {
 		gpt = true
 	}
 
+	partition u-boot {
+		offset = 1M
+		in-partition-table = "no"
+		image = "u-boot.rom"
+	}
+
 	partition rootfs {
 		offset = 2M
 		image = rootfs.ext4

board/kontron/smarc-sal28/readme.txt

@@ -71,3 +71,18 @@ You will see something like this at boot time:
 [    4.563565] GPT:Alternate GPT header not at the end of the disk.
 [    4.569596] GPT:266272 != 7864319
 [    4.572925] GPT: Use GNU Parted to correct GPT errors.
+
+Updating the bootloader
+=======================
+
+Buildroot will automatically build the u-boot bootloader. The resulting
+image is called u-boot.rom and you can find it in the images/ directory.
+
+To update the bootloader on the board you could either copy it to an
+USB thumb drive or you could put it on a TFTP server. The following
+example assumes you have the bootloader image copied to the root of
+a thumb drive:
+
+  # usb start
+  # load usb 0:1 $loadaddr u-boot.rom
+  # sf probe 0 && sf update $fileaddr 0x210000 $filesize