linux-kernel - Re: [PATCH v4 5/7] arm64: Unconditionally call unflatten_device

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Date: Tue, 27 Feb 2024 09:22:13 -0800
From: Oreoluwa Babatunde <quic_obabatun@...cinc.com>
To: Stephen Boyd <sboyd@...nel.org>, Rob Herring <robh+dt@...nel.org>
CC: <linux-kernel@...r.kernel.org>, <patches@...ts.linux.dev>,
        <linux-um@...ts.infradead.org>, <linux-arm-kernel@...ts.infradead.org>,
        <kunit-dev@...glegroups.com>, <linux-kselftest@...r.kernel.org>,
        <devicetree@...r.kernel.org>, Frank Rowand <frowand.list@...il.com>,
        Catalin
 Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Mark
 Rutland <mark.rutland@....com>
Subject: Re: [PATCH v4 5/7] arm64: Unconditionally call
 unflatten_device_tree()

On 2/16/2024 5:05 PM, Stephen Boyd wrote:

> Call this function unconditionally so that we can populate an empty DTB
> on platforms that don't boot with a firmware provided or builtin DTB.
> When ACPI is in use, unflatten_device_tree() ignores the
> 'initial_boot_params' pointer so the live DT on those systems won't be
> whatever that's pointing to. Similarly, when kexec copies the DT data
> the previous kernel to the new one on ACPI systems,
> of_kexec_alloc_and_setup_fdt() will ignore the live DT (the empty root
> one) and copy the 'initial_boot_params' data.
>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Frank Rowand <frowand.list@...il.com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: <linux-arm-kernel@...ts.infradead.org>
> Signed-off-by: Stephen Boyd <sboyd@...nel.org>

This change looks good to me. I am working on a patch set that will benefit from this.
Reviewed-by: Oreoluwa Babatunde <quic_obabatun@...cinc.com>

Regards,
Oreoluwa

> ---
>  arch/arm64/kernel/setup.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 42c690bb2d60..0d210720d47d 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -351,8 +351,7 @@ void __init __no_sanitize_address setup_arch(char **cmdline_p)
>  	/* Parse the ACPI tables for possible boot-time configuration */
>  	acpi_boot_table_init();
>  
> -	if (acpi_disabled)
> -		unflatten_device_tree();
> +	unflatten_device_tree();
>  
>  	bootmem_init();