[PATCH 08/25] u-boot: Separate out from kernel-arch.bbclass

[Richard Purdie <richard.purdie@linuxfoundation.org>]

Move the UBOOT_ARCH usage into u-boot.inc and stop using kernel-arch.bbclass
since there are things in there which u-boot might not want.

This does mean the ARCH and UBOOT_ARCH variables are no longer in the environment
but I hopefully covered the main uboot usages of the variables.

Also document where these values are from and what they're supposed to mean
explictly, including the difference between UBOOT_ARCH and UBOOT_ARCH_DIR.
UBOOT_ARCH_DIR has issues which will need discussion with newer platforms
which use dts/upstream.

You might think we need to set ARCH in EXTRA_OEMAKE for u-boot but it turns
out it was ignoring the value and setting it breaks builds. This patch
therefore doesn't do that after confirmation from the u-boot devs:

https://lists.u-boot-project.org/pipermail/u-boot/2026-July/627045.html

This is confirmed by the UBOOT_DTB patch which added the kernel-arch inherit
which is much later than when u-boot was established.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
 meta/lib/oe/kernel.py              | 2 ++
 meta/recipes-bsp/u-boot/u-boot.inc | 7 ++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/meta/lib/oe/kernel.py b/meta/lib/oe/kernel.py
index bab375c37ae..6c57ef402e8 100644
--- a/meta/lib/oe/kernel.py
+++ b/meta/lib/oe/kernel.py
@@ -38,6 +38,8 @@ def map_kernel_arch(d):
             return a
         bb.error("cannot map '%s' to a linux kernel architecture" % a)
 
+# Return a value for the -A parameter to u-boot's mkimage
+# This would be the value from the table in boot/image.c:uimage_arch
 def map_uboot_arch(d):
     a = map_kernel_arch(d)
 
diff --git a/meta/recipes-bsp/u-boot/u-boot.inc b/meta/recipes-bsp/u-boot/u-boot.inc
index a75948dfc34..3e2f5aa1a5f 100644
--- a/meta/recipes-bsp/u-boot/u-boot.inc
+++ b/meta/recipes-bsp/u-boot/u-boot.inc
@@ -6,7 +6,7 @@ PACKAGE_ARCH = "${MACHINE_ARCH}"
 DEPENDS += "${@bb.utils.contains('UBOOT_ENV_SUFFIX', 'scr', 'u-boot-mkimage-native', '', d)}"
 DEPENDS += "${@ 'u-boot-mkenvimage-native' if bb.utils.to_boolean(d.getVar('UBOOT_INITIAL_ENV_BINARY')) else ''}"
 
-inherit uboot-config uboot-extlinux-config uboot-sign deploy python3native kernel-arch
+inherit uboot-config uboot-extlinux-config uboot-sign deploy python3native
 
 DEPENDS += "swig-native"
 
@@ -34,6 +34,11 @@ UBOOT_INITIAL_ENV ?= "${PN}-initial-env"
 
 require u-boot-configure.inc
 
+UBOOT_ARCH = "${@oe.kernel.map_uboot_arch(d)}"
+# UBOOT_ARCH_DIR is the directory which contains the UBOOT_ARCH, i.e. the options are
+# the directories listed by "ls arch/" in the u-boot source. It is broken for platforms which
+# use dts/upstream.
+# arm contains arm and arm64.
 UBOOT_ARCH_DIR = "${@'arm' if d.getVar('UBOOT_ARCH').startswith('arm') else d.getVar('UBOOT_ARCH')}"
 do_compile () {
     unset LDFLAGS