linux-kernel - Re: [PATCH v3 04/13] dt-bindings: x86: Add CPU bindings for x86

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Message-ID: <20250504-happy-spoonbill-of-radiance-3b9fec@kuoka>
Date: Sun, 4 May 2025 18:45:59 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: x86@...nel.org, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Rob Herring <robh@...nel.org>, 
	"K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, 
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>, 
	Michael Kelley <mhklinux@...look.com>, devicetree@...r.kernel.org, 
	Saurabh Sengar <ssengar@...ux.microsoft.com>, Chris Oo <cho@...rosoft.com>, linux-hyperv@...r.kernel.org, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, 
	"Ravi V. Shankar" <ravi.v.shankar@...el.com>, Ricardo Neri <ricardo.neri@...el.com>
Subject: Re: [PATCH v3 04/13] dt-bindings: x86: Add CPU bindings for x86

On Sat, May 03, 2025 at 12:15:06PM GMT, Ricardo Neri wrote:
> Add bindings for CPUs in x86 architecture. Start by defining the `reg` and

What for?

> `enable-method` properties and their relationship to x86 APIC ID and the
> available mechanisms to boot secondary CPUs.
> 
> Start defining bindings for Intel processors. Bindings for other vendors
> can be added later as needed.
> 
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> ---

Not really tested so only limited review follows.

>  .../devicetree/bindings/x86/cpus.yaml         | 80 +++++++++++++++++++
>  1 file changed, 80 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/x86/cpus.yaml
> 
> diff --git a/Documentation/devicetree/bindings/x86/cpus.yaml b/Documentation/devicetree/bindings/x86/cpus.yaml
> new file mode 100644
> index 000000000000..108b3ad64aea
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/x86/cpus.yaml
> @@ -0,0 +1,80 @@
> +# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/x86/cpus.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: x86 CPUs
> +
> +maintainers:
> +  - Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
> +
> +description: |
> +  Description of x86 CPUs in a system through the "cpus" node.
> +
> +  Detailed information about the CPU architecture can be found in the Intel
> +  Software Developer's Manual:
> +    https://intel.com/sdm
> +
> +properties:
> +  compatible:
> +    enum:
> +      - intel,x86

That's architecture, not a CPU. CPUs are like 80286, 80386, so that's
not even specific instruction set. I don't get what you need it for.

> +
> +  reg:

Missing constraints.

> +    description: |

Do not need '|' unless you need to preserve formatting.

> +      Local APIC ID of the CPU. If the CPU has more than one execution thread,
> +      then the property is an array with one element per thread.
> +
> +  enable-method:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    description: |
> +      The method used to wake up secondary CPUs. This property is not needed if
> +      the secondary processors are booted using INIT assert, de-assert followed
> +      by Start-Up IPI messages as described in the Volume 3, Section 11.4 of
> +      Intel Software Developer's Manual.
> +
> +      It is also optional for the bootstrap CPU.
> +
> +    oneOf:

I see only one entry, so didn't you want an enum?

> +      - items:

Not a list

> +          - const: intel,wakeup-mailbox

So every vendor is supposed to come with different name for the same
feature? Or is wakeup-mailnox really intel specific, but then specific
to which processors?


> +            description: |
> +              CPUs are woken up using the mailbox mechanism. The platform
> +              firmware boots the secondary CPUs and puts them in a state
> +              to check the mailbox for a wakeup command from the operating
> +              system.
> +
> +required:
> +  - reg
> +  - compatible
> +
> +unevaluatedProperties: false

Missing ref in top-level or this is supposed to be additionalProps. See
example-schema.

> +
> +examples:
> +  - |
> +    /*
> +     * A system with two CPUs. cpu@0 is the bootstrap CPU and its status is
> +     * "okay". It does not have the enable-method property. cpu@1 is a
> +     * secondary CPU. Its status is "disabled" and defines the enable-method
> +     * property.
> +     */
> +
> +    cpus {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      cpu@0 {
> +        reg = <0x0 0x1>;
> +        compatible = "intel,x86";
> +        status = "okay";

Drop

> +      };
> +
> +      cpu@1 {
> +        reg = <0x0 0x1>;
> +        compatible = "intel,x86";
> +        status = "disabled";

Why?

Best regards,
Krzysztof