Re: [PATCH v6 09/25] arm: xenguest_arm64: Add a fake devicetree file

From: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>
To: Simon Glass <sjg@chromium.org>,
	U-Boot Mailing List <u-boot@lists.denx.de>
Cc: "Mark Kettenis" <mark.kettenis@xs4all.nl>,
	"Sean Anderson" <seanga2@gmail.com>,
	"Ilias Apalodimas" <ilias.apalodimas@linaro.org>,
	"Tom Rini" <trini@konsulko.com>,
	"François Ozog" <francois.ozog@linaro.org>,
	"Heinrich Schuchardt" <xypron.glpk@gmx.de>,
	"Albert Aribaud" <albert.u.boot@aribaud.net>,
	"Anastasiia Lukianenko" <anastasiia_lukianenko@epam.com>
Subject: Re: [PATCH v6 09/25] arm: xenguest_arm64: Add a fake devicetree file
Date: Thu, 2 Dec 2021 17:40:46 +0000	[thread overview]
Message-ID: <4c16a1e7-cea4-57da-94d9-88c47199bde0@epam.com> (raw)
In-Reply-To: <20211202155919.2429190-10-sjg@chromium.org>

Hi, Simon!

Sorry for being late to the party

On 02.12.21 17:59, Simon Glass wrote:
> Add an empty file to prevent build errors when building with
> CONFIG_OF_SEPARATE enabled.
>
> The build instructions in U-Boot do not provide enough detail to build a
> useful devicetree, unfortunately.
Xen guest doesn't use any built-in device trees as the guest's device tree is provided
by the Xen hypervisor itself and is generated at the virtual machine creation time: it is
populated with memory size, number of CPUs etc. based on [1].
So, even if we provide some device tree here it must not be used by U-boot at
the end of the day. Thus, it might be a reasonable solution to provide an empty device
tree as you do, but put a comment that it is not used.

Thank you,
Oleksandr
>
> Signed-off-by: Simon Glass <sjg@chromium.org>
> ---
>
> (no changes since v1)
>
>   arch/arm/dts/Makefile            |  2 ++
>   arch/arm/dts/xenguest-arm64.dts  | 15 +++++++++++++++
>   configs/xenguest_arm64_defconfig |  2 +-
>   3 files changed, 18 insertions(+), 1 deletion(-)
>   create mode 100644 arch/arm/dts/xenguest-arm64.dts
>
> diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
> index d53bae2c350..f6345988c8c 100644
> --- a/arch/arm/dts/Makefile
> +++ b/arch/arm/dts/Makefile
> @@ -1140,6 +1140,8 @@ dtb-$(CONFIG_ARCH_MEDIATEK) += \
>   	mt8516-pumpkin.dtb \
>   	mt8518-ap1-emmc.dtb
>   
> +dtb-$(CONFIG_XEN) += xenguest-arm64.dtb
> +
>   dtb-$(CONFIG_TARGET_GE_BX50V3) += \
>   	imx6q-bx50v3.dtb \
>   	imx6q-b850v3.dtb \
> diff --git a/arch/arm/dts/xenguest-arm64.dts b/arch/arm/dts/xenguest-arm64.dts
> new file mode 100644
> index 00000000000..52d3b062248
> --- /dev/null
> +++ b/arch/arm/dts/xenguest-arm64.dts
> @@ -0,0 +1,15 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Dummy devicetre file for xenguest_arm64
> + *
> + * This is required to make the board build with CONFIG OF_SEPARATE
> + * Build instructions at xenguest_arm64.rst are inadequate for obtaining a real
> + * devicetree.
> + *
> + * Copyright 2021 Google LLC
> + */
> +
> +/dts-v1/;
> +
> +/ {
> +};
> diff --git a/configs/xenguest_arm64_defconfig b/configs/xenguest_arm64_defconfig
> index 8d9d9133a2e..edce34346d3 100644
> --- a/configs/xenguest_arm64_defconfig
> +++ b/configs/xenguest_arm64_defconfig
> @@ -3,7 +3,7 @@ CONFIG_POSITION_INDEPENDENT=y
>   CONFIG_TARGET_XENGUEST_ARM64=y
>   CONFIG_SYS_TEXT_BASE=0x40080000
>   CONFIG_SYS_MALLOC_LEN=0x2000000
> -CONFIG_SYS_MALLOC_F_LEN=0x2000
> +CONFIG_DEFAULT_DEVICE_TREE="xenguest-arm64"
>   CONFIG_IDENT_STRING=" xenguest"
>   CONFIG_SYS_LOAD_ADDR=0x40000000
>   CONFIG_BOOTDELAY=10

[1] https://xenbits.xen.org/docs/unstable/man/xl.cfg.5.html