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arch/riscv: Add common FDT build

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Currently all platforms on RISC-V require a FDT.
The inclusion of the FDT is currently done in the platform Makefiles.
In order to factor out some common code this patch adds the inclusion
in the architecture Makefile. The FDT must be aligned to 8 byte
according to device tree spec. It avoids misaligned access.

Signed-off-by: Maximilian Brune <maximilian.brune@9elements.com>
Change-Id: I3b304a89646fe84c98e9f199f315bebb156de16c
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83848
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Matt DeVillier <matt.devillier@gmail.com>
This commit is contained in:
Maximilian Brune 2024-08-09 13:45:57 +02:00 • committed by Matt DeVillier
commit 7073ec43b0
2 changed files with 38 additions and 0 deletions
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15
src/arch/riscv/Kconfig
View file

@ -144,4 +144,19 @@ config RISCV_GET_HART_COUNT_AT_RUNTIME
SOC/Mainboards select this option in case the number of harts is not known at
build time. In this case the SOC must have a scheme in place to discover all harts.
config RISCV_DTS
bool
default n
help
This option is selected by mainboards that include a devicetree
source file (not to be confused with the coreboot devicetree.cb files).
The devicetree will be preprocessed and compiled into a FDT (flattened devicetree).
Said FDT will be put into a CBFS file for use in runtime.
config RISCV_DTS_FILE
string
depends on RISCV_DTS
help
Path to the devicetree source file in .dts format.
endif # if ARCH_RISCV

23
src/arch/riscv/Makefile.mk
View file

@ -67,6 +67,29 @@ all-y += \
$(top)/src/lib/memset.c
all-$(CONFIG_RISCV_USE_ARCH_TIMER) += arch_timer.c
## FDT (Flattened Devicetree) inclusion
ifeq ($(CONFIG_RISCV_DTS),y)
# at some point dtc may be compiled by our toolchain
DTC ?= dtc
CPPFLAGS_dts += -nostdinc -P -x assembler-with-cpp -I src/arch/riscv/include
$(obj)/preprocessed.dts: $(call strip_quotes, $(CONFIG_RISCV_DTS_FILE))
$(CPP_riscv) $(CPPFLAGS_dts) -o $@ $<
$(obj)/dtb: $(obj)/preprocessed.dts
$(DTC) -I dts -O dtb -o $@ $<
# This may be optimized in the future by letting cbfstool parse our FDT into a unflattened
# devicetree blob in build time, so that we only need to flatten it in runtime instead of
# unflatten and flatten it in runtime.
cbfs-files-y += DTB
DTB-file := $(obj)/dtb
DTB-type := raw
DTB-align := 8 # according to spec device trees needs to be 8 byte aligned
endif # CONFIG_RISCV_DTS
################################################################################
## bootblock