x86: Mention how to boot a 64-bit kernel from U-Boot
The README indicates that this is not supported, but this is no-longer true.
Update the text to indicate this and describe the FIT changes required.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/doc/uImage.FIT/kernel.its b/doc/uImage.FIT/kernel.its
index e668c3f..0aaf47e 100644
--- a/doc/uImage.FIT/kernel.its
+++ b/doc/uImage.FIT/kernel.its
@@ -85,3 +85,7 @@
};
};
};
+
+Note: the above assumes a 32-bit kernel. To directly boot a 64-bit kernel,
+change both arch values to "x86_64". U-Boot will then change to 64-bit mode
+before booting the kernel (see boot_linux_kernel()).