linux-kernel - Re: [PATCH v5 02/18] ACPI: processor: Set the ACPI

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Date: Fri, 12 Apr 2024 20:10:54 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: linux-pm@...r.kernel.org, loongarch@...ts.linux.dev, 
	linux-acpi@...r.kernel.org, linux-arch@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	kvmarm@...ts.linux.dev, x86@...nel.org, Russell King <linux@...linux.org.uk>, 
	"Rafael J . Wysocki" <rafael@...nel.org>, Miguel Luis <miguel.luis@...cle.com>, 
	James Morse <james.morse@....com>, Salil Mehta <salil.mehta@...wei.com>, 
	Jean-Philippe Brucker <jean-philippe@...aro.org>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, linuxarm@...wei.com, justin.he@....com, 
	jianyong.wu@....com
Subject: Re: [PATCH v5 02/18] ACPI: processor: Set the ACPI_COMPANION for the
 struct cpu instance

On Fri, Apr 12, 2024 at 4:38 PM Jonathan Cameron
<Jonathan.Cameron@...wei.com> wrote:
>
> The arm64 specific arch_register_cpu() needs to access the _STA
> method of the DSDT object so make it available by assigning the
> appropriate handle to the struct cpu instance.
>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  drivers/acpi/acpi_processor.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index 7a0dd35d62c9..93e029403d05 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -235,6 +235,7 @@ static int acpi_processor_get_info(struct acpi_device *device)
>         union acpi_object object = { 0 };
>         struct acpi_buffer buffer = { sizeof(union acpi_object), &object };
>         struct acpi_processor *pr = acpi_driver_data(device);
> +       struct cpu *c;
>         int device_declaration = 0;
>         acpi_status status = AE_OK;
>         static int cpu0_initialized;
> @@ -314,6 +315,8 @@ static int acpi_processor_get_info(struct acpi_device *device)
>                         cpufreq_add_device("acpi-cpufreq");
>         }
>
> +       c = &per_cpu(cpu_devices, pr->id);
> +       ACPI_COMPANION_SET(&c->dev, device);

This is also set for per_cpu(cpu_sys_devices, pr->id) in
acpi_processor_add(), via acpi_bind_one().

Moreover, there is some pr->id validation in acpi_processor_add(), so
it seems premature to use it here this way.

I think that ACPI_COMPANION_SET() should be called from here on
per_cpu(cpu_sys_devices, pr->id) after validating pr->id (so the
pr->id validation should all be done here) and then NULL can be passed
as acpi_dev to acpi_bind_one() in acpi_processor_add().  Then, there
will be one physical device corresponding to the processor ACPI device
and no confusion.

>         /*
>          *  Extra Processor objects may be enumerated on MP systems with
>          *  less than the max # of CPUs. They should be ignored _iff
> --
> 2.39.2
>