[PATCH 4/8] dts: Add alternative location for upstream DTB builds

[Simon Glass]

Hi Sumit,

On Thu, 14 Dec 2023 at 06:52, Sumit Garg <sumit.garg at linaro.org> wrote:
>
> Allow platform owners to mirror devicetree files from devitree-rebasing
> directory into dts/arch/$(ARCH) (special case for dts/arch/arm64). Then
> build then along with any *-u-boot.dtsi file present in arch/$(ARCH)/dts
> directory.

Also add a new Makefile for arm64.

>
> This will help easy migration for platforms which currently are compliant
> with upstream Linux kernel devicetree files.
>
> Signed-off-by: Sumit Garg <sumit.garg at linaro.org>
> ---
>  dts/Kconfig             | 11 +++++++++++
>  dts/Makefile            | 17 ++++++++++++++---
>  dts/arch/arm64/Makefile | 14 ++++++++++++++
>  3 files changed, 39 insertions(+), 3 deletions(-)
>  create mode 100644 dts/arch/arm64/Makefile
>
> diff --git a/dts/Kconfig b/dts/Kconfig
> index 00c0aeff893..96396f12b67 100644
> --- a/dts/Kconfig
> +++ b/dts/Kconfig
> @@ -85,6 +85,17 @@ config OF_LIVE
>           enables a live tree which is available after relocation,
>           and can be adjusted as needed.
>
> +config OF_UPSTREAM
> +       bool "Enable use of devicetree imported from Linux kernel release"
> +       help
> +         Traditionally, U-boot platforms used to have their custom devicetree

U-Boot

(I think I mentioned this, but you thought I said U-boot...but it
really is U-Boot). Perhaps grep your patches next time.

> +         files or copy devicetree files from Linux kernel which are hard to
> +         maintain and can usually get out-of-sync from Linux kernel. This
> +         option enables platforms to migrate to devicetree-rebasing repo where
> +         a regular sync will be maintained every major Linux kernel release
> +         cycle. However, platforms can still have some custom u-boot specific
> +         bits maintained as part of *-u-boot.dtsi files.

I'm a bit nervous about this. It means that boards chose between this
dir of the local files. It means there is some effort to switch.

I wonder if we could default to using the rebasing thing, with boards
having to 'opt out'? So this should be 'default y' ?


> +
>  choice
>         prompt "Provider of DTB for DT control"
>         depends on OF_CONTROL
> diff --git a/dts/Makefile b/dts/Makefile
> index 3437e54033d..8098bf8191a 100644
> --- a/dts/Makefile
> +++ b/dts/Makefile
> @@ -10,10 +10,20 @@ ifeq ($(DEVICE_TREE),)
>  DEVICE_TREE := unset
>  endif
>
> +ifeq ($(CONFIG_OF_UPSTREAM),y)
> +ifeq ($(CONFIG_ARM64),y)
> +DEVICE_TREE_LOC := dts/arch/arm64

dt_dir ?

Should we move the arm64 DTs to arch/arm64 ?

What about the subdirs used in Linux?

> +else
> +DEVICE_TREE_LOC := dts/arch/$(ARCH)
> +endif
> +else
> +DEVICE_TREE_LOC := arch/$(ARCH)/dts
> +endif
> +
>  ifneq ($(EXT_DTB),)
>  DTB := $(EXT_DTB)

>
>  else
> -DTB := arch/$(ARCH)/dts/$(DEVICE_TREE).dtb
> +DTB := $(DEVICE_TREE_LOC)/$(DEVICE_TREE).dtb
>  endif
>
>  $(obj)/dt-$(SPL_NAME).dtb: dts/dt.dtb $(objtree)/tools/fdtgrep FORCE
> @@ -41,7 +51,7 @@ $(DTB): arch-dtbs
>
>  PHONY += arch-dtbs
>  arch-dtbs:
> -       $(Q)$(MAKE) $(build)=arch/$(ARCH)/dts dtbs
> +       $(Q)$(MAKE) $(build)=$(DEVICE_TREE_LOC) dtbs
>
>  ifeq ($(CONFIG_SPL_BUILD),y)
>  obj-$(CONFIG_OF_EMBED) := dt-spl.dtb.o
> @@ -65,4 +75,5 @@ clean-files := dt.dtb.S
>  # Let clean descend into dts directories
>  subdir- += ../arch/arc/dts ../arch/arm/dts ../arch/m68k/dts ../arch/microblaze/dts     \
>            ../arch/mips/dts ../arch/nios2/dts ../arch/powerpc/dts ../arch/riscv/dts     \
> -          ../arch/sandbox/dts ../arch/sh/dts ../arch/x86/dts ../arch/xtensa/dts
> +          ../arch/sandbox/dts ../arch/sh/dts ../arch/x86/dts ../arch/xtensa/dts        \
> +          ./arch/arm64 ./arch/$(ARCH)
> diff --git a/dts/arch/arm64/Makefile b/dts/arch/arm64/Makefile
> new file mode 100644
> index 00000000000..16e9fea622d
> --- /dev/null
> +++ b/dts/arch/arm64/Makefile
> @@ -0,0 +1,14 @@
> +# SPDX-License-Identifier: GPL-2.0+
> +
> +include $(srctree)/scripts/Makefile.dts
> +
> +targets += $(dtb-y)
> +
> +# Add any required device tree compiler flags here
> +DTC_FLAGS += -a 0x8
> +
> +PHONY += dtbs
> +dtbs: $(addprefix $(obj)/, $(dtb-y))
> +       @:
> +
> +clean-files := */*.dtb */*.dtbo */*_HS
> --
> 2.34.1

Regards,
Simon