[PATCH 00/16] fdt: Make OF_BOARD a boolean option

Wed Oct 13 15:05:44 CEST 2021

Le mer. 13 oct. 2021 à 14:41, Andre Przywara <andre.przywara at arm.com> a
écrit :

> On Tue, 12 Oct 2021 19:01:04 -0600
> Simon Glass <sjg at chromium.org> wrote:
>
> Hi,
>
> > With Ilias' efforts we have dropped OF_PRIOR_STAGE and OF_HOSTFILE so
> > there are only three ways to obtain a devicetree:
> >
> >    - OF_SEPARATE - the normal way, where the devicetree is built and
> >       appended to U-Boot
> >    - OF_EMBED - for development purposes, the devicetree is embedded in
> >       the ELF file (also used for EFI)
> >    - OF_BOARD - the board figures it out on its own
> >
> > The last one is currently set up so that no devicetree is needed at all
> > in the U-Boot tree. Most boards do provide one, but some don't. Some
> > don't even provide instructions on how to boot on the board.
> >
> > The problems with this approach are documented at [1].
> >
> > In practice, OF_BOARD is not really distinct from OF_SEPARATE. Any board
> > can obtain its devicetree at runtime, even it is has a devicetree built
> > in U-Boot. This is because U-Boot may be a second-stage bootloader and
> its
> > caller may have a better idea about the hardware available in the
> machine.
> > This is the case with a few QEMU boards, for example.
> >
> > So it makes no sense to have OF_BOARD as a 'choice'. It should be an
> > option, available with either OF_SEPARATE or OF_EMBED.
>
> So I am possibly fine with that, but:
>
> > This series makes this change, adding various missing devicetree files
> > (and placeholders) to make the build work.
>
> If we just need it to make the build work, we not just have pure stub DTs,
> as you do for highbank, everywhere?
> Adding *some* DT files for those platforms that actually do the right
> thing seems like the wrong direction to me.
> Providing DTs in the source repositories of the actual consumers is more
> of a bad habit that dragged on since Linux started this around 10 years
> ago (for practical reasons). For *some* platforms U-Boot is the firmware
> component that is in the best situation to provide the DTB (because it's
> more than a mere bootloader), but for other it's just not. And this is not
> even looking at really dynamic platforms like QEMU, where providing some
> kind of fixed DT is just not working.
>
> I don't get the argument that people would need to see the DT in the tree
> to develop code. The DT spec and binding documentation (currently living
> in the Linux kernel source tree) provide the specification to code
> against, and the platform specific selection of drivers in Kconfig and
> _defconfig select the drivers for the devices that people are expected to
> see. Why does one need actual DT files in the tree?
>
> I totally agree on adding more documentation, possibly *pointing* to
> example
> DTs or giving commands on how to obtain the actual copy (-dumpdtb,
> /sys/firmware/devicetree), but don't think that adding some .dts files for
> platforms that don't need them is the right way.
>
> Cheers,
> Andre.

+1

>
>
> >
> > It also provides a few qemu clean-ups discovered along the way.
> >
> > This series is based on Ilias' two series for OF_HOSTFILE and
> > OF_PRIOR_STAGE removal.
> >
> > It is available at u-boot-dm/ofb-working
> >
> > [1]
> >
> https://patchwork.ozlabs.org/project/uboot/patch/20210919215111.3830278-3-sjg@chromium.org/
> >
> >
> > Simon Glass (16):
> >   arm: qemu: Mention -nographic in the docs
> >   arm: qemu: Explain how to extract the generate devicetree
> >   riscv: qemu: Explain how to extract the generate devicetree
> >   arm: qemu: Add a devicetree file for qemu_arm
> >   arm: qemu: Add a devicetree file for qemu_arm64
> >   riscv: qemu: Add devicetree files for qemu_riscv32/64
> >   arm: rpi: Add a devicetree file for rpi_4
> >   arm: vexpress: Add a devicetree file for juno
> >   arm: xenguest_arm64: Add a fake devicetree file
> >   arm: octeontx: Add a fake devicetree file
> >   arm: xilinx_versal_virt: Add a devicetree file
> >   arm: bcm7xxx: Add a devicetree file
> >   arm: qemu-ppce500: Add a devicetree file
> >   arm: highbank: Add a fake devicetree file
> >   fdt: Make OF_BOARD a bool option
> >   Drop CONFIG_BINMAN_STANDALONE_FDT
> >
> >  Makefile                               |    3 +-
> >  arch/arm/dts/Makefile                  |   20 +-
> >  arch/arm/dts/bcm2711-rpi-4-b.dts       | 1958 ++++++++++++++++++++++++
> >  arch/arm/dts/bcm7xxx.dts               |   15 +
> >  arch/arm/dts/highbank.dts              |   14 +
> >  arch/arm/dts/juno-r2.dts               | 1038 +++++++++++++
> >  arch/arm/dts/octeontx.dts              |   14 +
> >  arch/arm/dts/qemu-arm.dts              |  402 +++++
> >  arch/arm/dts/qemu-arm64.dts            |  381 +++++
> >  arch/arm/dts/xenguest-arm64.dts        |   15 +
> >  arch/arm/dts/xilinx-versal-virt.dts    |  307 ++++
> >  arch/powerpc/dts/Makefile              |    1 +
> >  arch/powerpc/dts/qemu-ppce500.dts      |  264 ++++
> >  arch/riscv/dts/Makefile                |    2 +-
> >  arch/riscv/dts/qemu-virt.dts           |    8 -
> >  arch/riscv/dts/qemu-virt32.dts         |  217 +++
> >  arch/riscv/dts/qemu-virt64.dts         |  217 +++
> >  configs/bcm7260_defconfig              |    1 +
> >  configs/bcm7445_defconfig              |    1 +
> >  configs/highbank_defconfig             |    2 +-
> >  configs/octeontx2_95xx_defconfig       |    1 +
> >  configs/octeontx2_96xx_defconfig       |    1 +
> >  configs/octeontx_81xx_defconfig        |    1 +
> >  configs/octeontx_83xx_defconfig        |    1 +
> >  configs/qemu-ppce500_defconfig         |    2 +
> >  configs/qemu-riscv32_defconfig         |    1 +
> >  configs/qemu-riscv32_smode_defconfig   |    1 +
> >  configs/qemu-riscv32_spl_defconfig     |    4 +-
> >  configs/qemu-riscv64_defconfig         |    1 +
> >  configs/qemu-riscv64_smode_defconfig   |    1 +
> >  configs/qemu-riscv64_spl_defconfig     |    3 +-
> >  configs/qemu_arm64_defconfig           |    1 +
> >  configs/qemu_arm_defconfig             |    1 +
> >  configs/rpi_4_32b_defconfig            |    1 +
> >  configs/rpi_4_defconfig                |    1 +
> >  configs/rpi_arm64_defconfig            |    1 +
> >  configs/vexpress_aemv8a_juno_defconfig |    1 +
> >  configs/xenguest_arm64_defconfig       |    1 +
> >  configs/xilinx_versal_virt_defconfig   |    1 +
> >  doc/board/emulation/qemu-arm.rst       |   19 +-
> >  doc/board/emulation/qemu-riscv.rst     |   12 +
> >  dts/Kconfig                            |   27 +-
> >  tools/binman/binman.rst                |   20 -
> >  43 files changed, 4922 insertions(+), 61 deletions(-)
> >  create mode 100644 arch/arm/dts/bcm2711-rpi-4-b.dts
> >  create mode 100644 arch/arm/dts/bcm7xxx.dts
> >  create mode 100644 arch/arm/dts/highbank.dts
> >  create mode 100644 arch/arm/dts/juno-r2.dts
> >  create mode 100644 arch/arm/dts/octeontx.dts
> >  create mode 100644 arch/arm/dts/qemu-arm.dts
> >  create mode 100644 arch/arm/dts/qemu-arm64.dts
> >  create mode 100644 arch/arm/dts/xenguest-arm64.dts
> >  create mode 100644 arch/arm/dts/xilinx-versal-virt.dts
> >  create mode 100644 arch/powerpc/dts/qemu-ppce500.dts
> >  delete mode 100644 arch/riscv/dts/qemu-virt.dts
> >  create mode 100644 arch/riscv/dts/qemu-virt32.dts
> >  create mode 100644 arch/riscv/dts/qemu-virt64.dts
> >
>
> --
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