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fdt: Avoid emitting an device tree when not needed

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U-Boot always needs some sort of a device tree in the build. Some boards
never actually use this, at least in production systems, since a prior
firmware stage sets one up and passes it to U-Boot. At present the only
mechanism to do that is with custom function (OF_BOARD), but future work
will include a standard way of doing this ('standard passage').

It can be confusing to see a device tree emitted from the U-Boot build in
this situation. Add an option to drop it.

Signed-off-by: Simon Glass <sjg@chromium.org>
This commit is contained in:
Simon Glass 2021-12-16 20:59:38 -07:00 • committed by Tom Rini
parent 24f073d400
commit b7d8e85b4c
2 changed files with 14 additions and 2 deletions
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6
Makefile
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@ -944,7 +944,9 @@ INPUTS-$(CONFIG_SPL_FRAMEWORK) += u-boot.img
endif
endif
INPUTS-$(CONFIG_TPL) += tpl/u-boot-tpl.bin
INPUTS-$(CONFIG_OF_SEPARATE) += u-boot.dtb
# Allow omitting the .dtb output if it is not normally used
INPUTS-$(CONFIG_OF_SEPARATE) += $(if $(CONFIG_OF_OMIT_DTB),dts/dt.dtb,u-boot.dtb)
ifeq ($(CONFIG_SPL_FRAMEWORK),y)
INPUTS-$(CONFIG_OF_SEPARATE) += u-boot-dtb.img
endif
@ -1187,7 +1189,7 @@ u-boot.bin: u-boot-fit-dtb.bin FORCE
u-boot-dtb.bin: u-boot-nodtb.bin dts/dt.dtb FORCE
$(call if_changed,cat)
else ifeq ($(CONFIG_OF_SEPARATE),y)
else ifeq ($(CONFIG_OF_SEPARATE).$(CONFIG_OF_OMIT_DTB),y.)
u-boot-dtb.bin: u-boot-nodtb.bin dts/dt.dtb FORCE
$(call if_changed,cat)

10
dts/Kconfig
View file

@ -129,6 +129,16 @@ config OF_HAS_PRIOR_STAGE
Note: This option must be set in Kconfig and cannot be enabled or
disabled in the board's defconfig file.
config OF_OMIT_DTB
bool "Omit the device tree output when building"
default y if OF_HAS_PRIOR_STAGE && !BINMAN
help
As a special case, avoid writing a device tree file u-boot.dtb when
building. Also don't include that file in u-boot.bin
This is used for boards which normally provide a devicetree via a
runtime mechanism (such as OF_BOARD), to avoid confusion.
config DEFAULT_DEVICE_TREE
string "Default Device Tree for DT control"
depends on OF_CONTROL