kbuild: cherry-pick kbuild fdtoverlay changes from linux

Linux commits:
15d16d6dadf6 kbuild: Add generic rule to apply fdtoverlay
44f87191d105 kbuild: parameterize the .o part of suffix-search

The Linux commit 15d16d6dadf6 adds a generic rule in Makefile.lib
to automatically apply fdtoverlay, so that each platform doesn't
need to include a complex rule. This also automatically appends
DTC_FLAGS_foo_base += -@ to all base files

The platform's Makefile only needs to have this now:

foo-dtbs := foo_base.dtb foo_overlay1.dtbo foo_overlay2.dtbo
dtb-y := foo.dtb

Signed-off-by: Prasad Kummari <prasad.kummari@amd.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20240906070808.1045991-2-prasad.kummari@amd.com

3 files changed, 32 insertions, 0 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 62e0207f91b..5daceb26061 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -32,6 +32,10 @@ baseprereq = $(basename $(notdir $<))
 escsq = $(subst $(squote),'\$(squote)',$1)
 
 ###
+# real prerequisites without phony targets
+real-prereqs = $(filter-out $(PHONY), $^)
+
+###
 # Easy method for doing a status message
        kecho := :
  quiet_kecho := echo
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 99cc29595b4..90aed148c44 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -293,6 +293,7 @@ $(obj)/%.o: $(src)/%.S FORCE
 
 targets += $(real-objs-y) $(real-objs-m) $(lib-y)
 targets += $(extra-y) $(MAKECMDGOALS) $(always)
+targets += $(real-dtb-y) $(lib-y) $(always-y)
 
 # Linker scripts preprocessor (.lds.S -> .lds)
 # ---------------------------------------------------------------------------
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 5dfb4b6e46f..54403040f00 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -47,6 +47,13 @@ obj-m		:= $(filter-out %/, $(obj-m))
 
 subdir-ym	:= $(sort $(subdir-y) $(subdir-m))
 
+# Expand $(foo-objs) $(foo-y) etc. by replacing their individuals
+suffix-search = $(strip $(foreach s, $3, $($(1:%$(strip $2)=%$s))))
+# List composite targets that are constructed by combining other targets
+multi-search = $(sort $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $m)))
+# List primitive targets that are compiled from source files
+real-search = $(foreach m, $1, $(if $(call suffix-search, $m, $2, $3 -), $(call suffix-search, $m, $2, $3), $m))
+
 # if $(foo-objs) exists, foo.o is a composite object
 multi-used-y := $(sort $(foreach m,$(obj-y), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))), $(m))))
 multi-used-m := $(sort $(foreach m,$(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y))), $(m))))
@@ -58,6 +65,13 @@ single-used-m := $(sort $(filter-out $(multi-used-m),$(obj-m)))
 multi-objs-y := $(foreach m, $(multi-used-y), $($(m:.o=-objs)) $($(m:.o=-y)))
 multi-objs-m := $(foreach m, $(multi-used-m), $($(m:.o=-objs)) $($(m:.o=-y)))
 
+# Composite DTB (i.e. DTB constructed by overlay)
+multi-dtb-y := $(call multi-search, $(dtb-y), .dtb, -dtbs)
+# Primitive DTB compiled from *.dts
+real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
+# Base DTB that overlay is applied onto (each first word of $(*-dtbs) expansion)
+base-dtb-y := $(foreach m, $(multi-dtb-y), $(firstword $(call suffix-search, $m, .dtb, -dtbs)))
+
 # $(subdir-obj-y) is the list of objects in $(obj-y) which uses dir/ to
 # tell kbuild to descend
 subdir-obj-y := $(filter %/built-in.o, $(obj-y))
@@ -69,6 +83,7 @@ real-objs-m := $(foreach m, $(obj-m), $(if $(strip $($(m:.o=-objs)) $($(m:.o=-y)
 # Add subdir path
 
 extra-y		:= $(addprefix $(obj)/,$(extra-y))
+always-y        := $(addprefix $(obj)/,$(always-y))
 always		:= $(addprefix $(obj)/,$(always))
 targets		:= $(addprefix $(obj)/,$(targets))
 modorder	:= $(addprefix $(obj)/,$(modorder))
@@ -83,6 +98,8 @@ multi-used-y	:= $(addprefix $(obj)/,$(multi-used-y))
 multi-used-m	:= $(addprefix $(obj)/,$(multi-used-m))
 multi-objs-y	:= $(addprefix $(obj)/,$(multi-objs-y))
 multi-objs-m	:= $(addprefix $(obj)/,$(multi-objs-m))
+multi-dtb-y	:= $(addprefix $(obj)/,$(multi-dtb-y))
+real-dtb-y      := $(addprefix $(obj)/,$(real-dtb-y))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 
 # These flags are needed for modversions and compiling, so we define them here
@@ -301,6 +318,9 @@ endif
 
 DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
 
+# Set -@ if the target is a base DTB that overlay is applied onto
+DTC_FLAGS += $(if $(filter $(patsubst $(obj)/%,%,$@), $(base-dtb-y)), -@)
+
 # Generate an assembly file to wrap the output of the device tree compiler
 quiet_cmd_dt_S_dtb= DTBS    $@
 # Modified for U-Boot
@@ -422,6 +442,13 @@ cmd_dtco = mkdir -p $(dir ${dtc-tmp}) ; \
 $(obj)/%.dtbo: $(src)/%.dtso $(DTC) FORCE
 	$(call if_changed_dep,dtco)
 
+quiet_cmd_fdtoverlay = DTOVL   $@
+           cmd_fdtoverlay = fdtoverlay -o $@ -i $(real-prereqs)
+
+$(multi-dtb-y): FORCE
+	$(call if_changed,fdtoverlay)
+$(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)
+
 # Fonts
 # ---------------------------------------------------------------------------