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Message-ID: <20240131205405.GA2249327-robh@kernel.org>
Date: Wed, 31 Jan 2024 14:54:05 -0600
From: Rob Herring <robh@...nel.org>
To: Stephen Boyd <sboyd@...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 v2 1/7] arm64: Unconditionally call
unflatten_device_tree()
On Mon, Jan 29, 2024 at 04:45:00PM -0800, 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.
> Override 'initial_boot_params' to NULL when ACPI is in use but the
> bootloader has loaded a DTB so that we don't allow both ACPI and DT to
> be used during boot. If there isn't a valid initial_boot_params dtb then
> unflatten_device_tree() returns early so this is fine.
>
> 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>
> ---
> arch/arm64/kernel/setup.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index 417a8a86b2db..ffb1942724ae 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -351,8 +351,11 @@ 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();
> + /* Don't use the FDT from boot if ACPI is in use */
> + if (!acpi_disabled)
> + initial_boot_params = NULL;
I still think this is a problem for kexec. See
of_kexec_alloc_and_setup_fdt(). You see it uses initial_boot_params. At
first glance it looks like it would just write out everything we need.
But for UEFI boot, I think we need all the chosen properties like
linux,uefi-mmap-start preserved from the current boot for the next
kernel we kexec.
I think you'll have to check acpi_disabled in unflatten_device_tree()
and unflatten the empty tree leaving initial_boot_params alone. That
means our FDT and unflattened tree will be different DTs, but I think
that's fine.
Rob
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