Support using u-boot with Image format for raspberrypi3-64

For raspberrypi3-64 we need to use the Image or Image.gz format with u-boot
instead of the legacy uImage format. We also need to issue the 'booti' command
to boot the kernel instead of 'bootm'.

Signed-off-by: Paul Barker <pbarker@toganlabs.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/docs/extra-build-config.md b/docs/extra-build-config.md
index 8d4f897..380d969 100644
--- a/docs/extra-build-config.md
+++ b/docs/extra-build-config.md
@@ -105,10 +105,12 @@ To disable rpi boot logo, set this variable in local.conf:
 
 To have u-boot load kernel image, set in your local.conf:
 
-    KERNEL_IMAGETYPE = "uImage"
+    RPI_USE_U_BOOT = "1"
 
-This will make kernel.img be u-boot image which will load uImage. By default,
-kernel.img is the actual kernel image (ex. Image).
+This will select the appropriate image format for use with u-boot automatically.
+For further customisation the KERNEL_IMAGETYPE and KERNEL_BOOTCMD variables can
+be overridden to select the exact kernel image type (eg. zImage) and u-boot
+command (eg. bootz) to be used.
 
 ## Image with Initramfs