Re: [Buildroot] [PATCH v2 2/2] board/zynqmp: add custom board documentation

[Luca Ceresoli via buildroot <buildroot@buildroot.org>]

On Tue, 17 Jun 2025 15:15:34 +0100
Neal Frager <neal.frager@amd.com> wrote:

> The readme.txt file for zynqmp boards does not have documentation for working
> with custom boards.  This patch adds documentation for custom board support.
> 
> Signed-off-by: Neal Frager <neal.frager@amd.com>
> ---
> V1->V2:
> - correct copy paste error as the output directory of step 3 should be:
>     output/build/uboot-custom/board/xilinx/zynqmp/custom_hw_platform/
>   and not:
>     output/build/uboot-custom/board/xilinx/zynq/custom_hw_platform/
> ---
>  board/zynqmp/readme.txt | 41 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
> 
> diff --git a/board/zynqmp/readme.txt b/board/zynqmp/readme.txt
> index 3f1b3a80c2..a98ff78f6f 100644
> --- a/board/zynqmp/readme.txt
> +++ b/board/zynqmp/readme.txt
> @@ -65,6 +65,47 @@ Where 'sdX' is the device node of the SD.
>  
>  Eject the SD card, insert it in the board, and power it up.
>  
> +Support for other boards:
> +=========================
> +
> +If you want to build a system for other boards based on the same SoC, and the
> +board is already supported by the upstream kernel and U-Boot, you simply need
> +to change the following Buildroot options:
> +
> + - Kernel Device Tree file name (BR2_LINUX_KERNEL_INTREE_DTS_NAME)
> + - U-Boot (BR2_TARGET_UBOOT_CUSTOM_MAKEOPTS="DEVICE_TREE=<dts file name>")
> +
> +Custom psu_init_gpl.c/h support:
> +
> +To generate a working boot.bin image, psu_init_gpl.c/h are required in
> +the U-Boot source tree. Without those files, boot.bin will be built
> +successfully but it will not be functional at all. Those files are
> +output from the Xilinx tools, but for convenience, U-Boot includes the
> +default psu_init_gpl.c/h of popular boards. Those files may need to be
> +updated for any programmable logic or DDR customizations which impact
> +psu_init (clock/pin setup & mapping/AXI bridge setup/etc). See
> +board/xilinx/zynqmp/ directory of U-Boot for natively supported psu_init
> +files. If the psu_init files for your board are not found in U-Boot,
> +you need to add them by yourself.
> +
> +1) Start with a defconfig supported by Buildroot (e.g. ZCU106)
> +    make zynqmp_zcu106_defconfig
> +
> +2) make uboot-menuconfig
> +    Visit the following menu and enable CONFIG_XILINX_PS_INIT_FILE
> +
> +    ARM architecture  --->
> +       [*] Zynq/ZynqMP PS init file(s) location

CONFIG_XILINX_PS_INIT_FILE is a string, not a bool. But this might be
irrelevant, see below.

> +3) Copy psu_init_gpl.c/h generated by the Xilinx Vivado tools into
> +   output/build/uboot-custom/board/xilinx/zynqmp/custom_hw_platform/

Ain't this automated in Buildroot by
BR2_TARGET_UBOOT_ZYNQMP_PSU_INIT_FILE? There should be no manual step
needed. Am I missing something?

> +4) make
> +
> +Note: The files in step 3 will need to be re-copied after cleaning the
> +output directory and at this time, there is no way to save them as
> +part of the buildroot configuration, except as a U-Boot patch.

If such manual step were needed, that would be a huge hole in Buildroot
that needs to be fixed.

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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