linux-kernel - Re: [PATCH v8 1/2] of: Documentation: Specify local APIC ID in "reg"

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Date:   Sun, 25 Mar 2018 18:50:39 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Ivan Gorinov <ivan.gorinov@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Frank Rowand <frowand.list@...il.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v8 1/2] of: Documentation: Specify local APIC ID in "reg"

On Thu, Mar 22, 2018 at 4:35 PM, Ivan Gorinov <ivan.gorinov@...el.com> wrote:
> Use the "reg" property to specify the processor's local APIC ID instead of
> setting it to the CPU node index in Device Tree.
>
> Local APIC ID is assigned by hardware and visible in the APIC ID register.
> Some processor models allow APIC ID to be changed by software, but CPUID
> instruction executed with %eax = 0x0b always returns the initial ID in %edx.
>
> Local APIC ID does not match the node index in many systems.
>
> Signed-off-by: Ivan Gorinov <ivan.gorinov@...el.com>
> ---
>  Documentation/devicetree/bindings/x86/ce4100.txt | 37 ++++++++++++++++++------
>  1 file changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/x86/ce4100.txt b/Documentation/devicetree/bindings/x86/ce4100.txt
> index b49ae59..4bbfed1 100644
> --- a/Documentation/devicetree/bindings/x86/ce4100.txt
> +++ b/Documentation/devicetree/bindings/x86/ce4100.txt
> @@ -7,17 +7,36 @@ Many of the "generic" devices like HPET or IO APIC have the ce4100
>  name in their compatible property because they first appeared in this
>  SoC.
>
> -The CPU node
> -------------
> -       cpu@0 {
> -               device_type = "cpu";
> -               compatible = "intel,ce4100";
> -               reg = <0>;
> -               lapic = <&lapic0>;
> +The CPU nodes
> +-------------
> +
> +       cpus {
> +               #address-cells = <1>;
> +               #size-cells = <0>;
> +
> +               cpu@...0 {

As I mentioned on prior versions, drop the '0x' and leading zeros.

Otherwise,

Reviewed-by: Rob Herring <robh@...nel.org>

> +                       device_type = "cpu";
> +                       compatible = "intel,ce4100";
> +                       reg = <0x00>;
> +               };
> +
> +               cpu@...2 {
> +                       device_type = "cpu";
> +                       compatible = "intel,ce4100";
> +                       reg = <0x02>;
> +               };
>         };
>
> -The reg property describes the CPU number. The lapic property points to
> -the local APIC timer.
> +A "cpu" node describes one logical processor (hardware thread).
> +
> +Required properties:
> +
> +- device_type
> +       Device type, must be "cpu".
> +
> +- reg
> +       Local APIC ID, the unique number assigned to each processor by
> +       system hardware.
>
>  The SoC node
>  ------------
> --
> 2.7.4
>