[PATCH v2 1/2] dts: Add ability to build fallback DTBOs from arch/$(ARCH)/dts

[Marek Vasut]

Currently the enablement of OF_UPSTREAM results on the build system
searching for DTs only in dts/upstream/ . There are platforms which
use U-Boot specific DTBOs applied on top of U-Boot control DT during
SPL stage, and source DTs for these are located in arch/$(ARCH)/dtb.

Add dedicated 'dtbos' target which builds only .dtbos and not .dtbs and
in case CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS is enabled, build
this target for arch/$(ARCH)/dtb to generate local U-Boot specific DTBOs.

Adjust top level Makefile so binman would search for .dtb and .dtbo in
both OF_UPSTREAM specific paths and arch/$(ARCH)/dtb for the .dtbo case
in case CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS is enabled.

Signed-off-by: Marek Vasut <marex at denx.de>
---
Cc: "NXP i.MX U-Boot Team" <uboot-imx at nxp.com>
Cc: Caleb Connolly <caleb.connolly at linaro.org>
Cc: Christoph Niedermaier <cniedermaier at dh-electronics.com>
Cc: Fabio Estevam <festevam at gmail.com>
Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
Cc: Jonas Karlman <jonas at kwiboo.se>
Cc: Lothar Rubusch <l.rubusch at gmail.com>
Cc: Michal Simek <michal.simek at amd.com>
Cc: Nobuhiro Iwamatsu <iwamatsu at nigauri.org>
Cc: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
Cc: Simon Glass <sjg at chromium.org>
Cc: Stefano Babic <sbabic at denx.de>
Cc: Sumit Garg <sumit.garg at linaro.org>
Cc: Tom Rini <trini at konsulko.com>
Cc: u-boot at dh-electronics.com
Cc: u-boot at lists.denx.de
---
V2: Gate this functionality behind CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS
---
NOTE: Depends on https://lore.kernel.org/u-boot/20241004001118.322531-1-marex@denx.de/
---
 Makefile             |  4 ++++
 dts/Kconfig          | 16 ++++++++++++++++
 dts/Makefile         | 14 +++++++++++++-
 scripts/Makefile.dts |  6 ++++++
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index af24de4165e..a5258e8cb3f 100644
--- a/Makefile
+++ b/Makefile
@@ -1375,7 +1375,11 @@ of_list := "$(ext_dtb_list)"
 of_list_dirs := $(dir $(EXT_DTB))
 else
 of_list := $(CONFIG_OF_LIST)
+ifneq ($(CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS),)
+of_list_dirs := $(dt_dir) arch/$(ARCH)/dts
+else
 of_list_dirs := $(dt_dir)
+endif
 default_dt := $(if $(DEVICE_TREE),$(DEVICE_TREE),$(CONFIG_DEFAULT_DEVICE_TREE))
 endif
 
diff --git a/dts/Kconfig b/dts/Kconfig
index 569d4be338e..385058b429f 100644
--- a/dts/Kconfig
+++ b/dts/Kconfig
@@ -125,6 +125,22 @@ config OF_UPSTREAM_VENDOR
 	help
 	  Select the vendor to build all devicetree files for.
 
+config OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS
+	bool "Build local DTBOs as fallback for DTBOs missing upstream"
+	default n
+	depends on OF_UPSTREAM
+	help
+	  Enable building DTBOs from arch/$(ARCH)/dts as a fallback for
+	  DTBOs which are not part of Linux kernel upstream yet. This is
+	  a stopgap measure to expedite OF_UPSTREAM switch for platforms
+	  which already have main DT in Linux kernel upstream, but still
+	  have leftover DTBOs in U-Boot tree.
+
+	  Do not use this option, upstream your DTs and DTBOs instead.
+	  If the upstreaming is in progress, use with utmost caution.
+
+	  If unsure, say N.
+
 choice
 	prompt "Provider of DTB for DT control"
 	depends on OF_CONTROL
diff --git a/dts/Makefile b/dts/Makefile
index d6c2c9daf31..32c749a043a 100644
--- a/dts/Makefile
+++ b/dts/Makefile
@@ -11,12 +11,18 @@ DEVICE_TREE := unset
 endif
 
 ifeq ($(CONFIG_OF_UPSTREAM),y)
+ifneq ($(CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS),)
+local_dtbos := local-dtbos
+else
+local_dtbos :=
+endif
 ifeq ($(CONFIG_ARM64),y)
 dt_dir := dts/upstream/src/arm64
 else
 dt_dir := dts/upstream/src/$(ARCH)
 endif
 else
+local_dtbos :=
 dt_dir := arch/$(ARCH)/dts
 endif
 
@@ -40,7 +46,7 @@ endif
 
 targets += dt.dtb
 
-$(DTB): arch-dtbs
+$(DTB): arch-dtbs $(local_dtbos)
 	$(Q)test -e $@ || (						\
 	echo >&2;							\
 	echo >&2 "Device Tree Source ($@) is not correctly specified.";	\
@@ -53,6 +59,12 @@ PHONY += arch-dtbs
 arch-dtbs:
 	$(Q)$(MAKE) $(build)=$(dt_dir) dtbs
 
+ifneq ($(CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS),)
+PHONY += local-dtbos
+local-dtbos:
+	$(Q)$(MAKE) $(build)=arch/$(ARCH)/dts dtbos
+endif
+
 ifeq ($(CONFIG_SPL_BUILD),y)
 obj-$(CONFIG_OF_EMBED) := dt-spl.dtb.o
 # support "out-of-tree" build for dtb-spl
diff --git a/scripts/Makefile.dts b/scripts/Makefile.dts
index 1fe142f2bbf..3ab67b3c247 100644
--- a/scripts/Makefile.dts
+++ b/scripts/Makefile.dts
@@ -21,4 +21,10 @@ PHONY += dtbs
 dtbs: $(addprefix $(obj)/, $(dtb-y))
 	@:
 
+ifneq ($(CONFIG_OF_UPSTREAM_INCLUDE_LOCAL_FALLBACK_DTBOS),)
+PHONY += dtbos
+dtbos: $(addprefix $(obj)/, $(filter-out %.dtb,$(dtb-y)))
+	@:
+endif
+
 clean-files := *.dtb *.dtbo */*.dtb */*.dtbo *_HS
-- 
2.45.2