linux-kernel - Re: [RFT PATCH v1 2/4] dt-binding: cpu-topology: Move cpu-map to a common binding.

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Date:   Mon, 3 Dec 2018 09:40:21 -0800
From:   Atish Patra <atish.patra@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Albert Ou <aou@...s.berkeley.edu>,
        Anup Patel <anup@...infault.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Catalin Marinas <catalin.marinas@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Dmitriy Cherkasov <dmitriy@...-tech.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Juri Lelli <juri.lelli@....com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        Mark Rutland <mark.rutland@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will.deacon@....com>
Subject: Re: [RFT PATCH v1 2/4] dt-binding: cpu-topology: Move cpu-map to a
 common binding.

On 12/3/18 9:33 AM, Sudeep Holla wrote:
> On Mon, Dec 03, 2018 at 09:23:42AM -0800, Atish Patra wrote:
>> On 12/3/18 8:55 AM, Sudeep Holla wrote:
>>> On Thu, Nov 29, 2018 at 03:28:18PM -0800, Atish Patra wrote:
>>>> cpu-map binding can be used to described cpu topology for both
>>>> RISC-V & ARM. It makes more sense to move the binding to document
>>>> to a common place.
>>>>
>>>> The relevant discussion can be found here.
>>>> https://lkml.org/lkml/2018/11/6/19
>>>>
>>>
>>> Looks good to me apart from a minor query below in the example.
>>>
>>> Reviewed-by: Sudeep Holla <sudeep.holla@....com>
>>>
>>>> Signed-off-by: Atish Patra <atish.patra@....com>
>>>> ---
>>>>    .../{arm/topology.txt => cpu/cpu-topology.txt}     | 81 ++++++++++++++++++----
>>>>    1 file changed, 67 insertions(+), 14 deletions(-)
>>>>    rename Documentation/devicetree/bindings/{arm/topology.txt => cpu/cpu-topology.txt} (86%)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/arm/topology.txt b/Documentation/devicetree/bindings/cpu/cpu-topology.txt
>>>> similarity index 86%
>>>> rename from Documentation/devicetree/bindings/arm/topology.txt
>>>> rename to Documentation/devicetree/bindings/cpu/cpu-topology.txt
>>>> index 66848355..1de6fbce 100644
>>>> --- a/Documentation/devicetree/bindings/arm/topology.txt
>>>> +++ b/Documentation/devicetree/bindings/cpu/cpu-topology.txt
>>>
>>> [...]
>>>
>>>> +Example 3: HiFive Unleashed (RISC-V 64 bit, 4 core system)
>>>> +
>>>> +cpus {
>>>> +	#address-cells = <2>;
>>>> +	#size-cells = <2>;
>>>> +	compatible = "sifive,fu540g", "sifive,fu500";
>>>> +	model = "sifive,hifive-unleashed-a00";
>>>> +
>>>> +	...
>>>> +
>>>> +	cpu-map {
>>>> +		cluster0 {
>>>> +			core0 {
>>>> +				cpu = <&L12>;
>>>> +		 	};
>>>> +			core1 {
>>>> +				cpu = <&L15>;
>>>> +			};
>>>> +			core2 {
>>>> +				cpu0 = <&L18>;
>>>> +			};
>>>> +			core3 {
>>>> +				cpu0 = <&L21>;
>>>> +			};
>>>> +		};
>>>> + 	};
>>>> +
>>>> +	L12: cpu@1 {
>>>> +		device_type = "cpu";
>>>> +		compatible = "sifive,rocket0", "riscv";
>>>> +		reg = <0x1>;
>>>> +	}
>>>> +
>>>> +	L15: cpu@2 {
>>>> +		device_type = "cpu";
>>>> +		compatible = "sifive,rocket0", "riscv";
>>>> +		reg = <0x2>;
>>>> +	}
>>>> +	L18: cpu@3 {
>>>> +		device_type = "cpu";
>>>> +		compatible = "sifive,rocket0", "riscv";
>>>> +		reg = <0x3>;
>>>> +	}
>>>> +	L21: cpu@4 {
>>>> +		device_type = "cpu";
>>>> +		compatible = "sifive,rocket0", "riscv";
>>>> +		reg = <0x4>;
>>>> +	}
>>>> +};
>>>
>>> The labels for the CPUs drew my attention. Is it intentionally random
>>> (or even specific) or just chosen to show anything can be used as labels ?
>>
>> SiFive generates the device tree from RTL directly. So I am not sure if they
>> assign random numbers or a particular algorithm chooses the label. I tried
>> to put the exact ones that is available publicly.
>>
>> https://github.com/riscv/riscv-device-tree-doc/blob/master/examples/sifive-hifive_unleashed-microsemi.dts
> 
> Cool, love that. So you don't have the problem I was trying to explain.
> But I still see the possibility of some other RISC-V vendor copy-pasting
> from here ;). Anyways it's left to you.
> 

I am fine with either way. I hoped other vendors won't blindly copy as 
this example was specific to HiFive Unleashed board. But I get your 
point. As this DT entry is a generic architecture entry, we should have 
generic examples instead of platform specific examples.

I will change it to a generic one.


Regards,
Atish
> --
> Regards,
> Sudeep
>