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Subject: Re: [RFT PATCH v1 2/4] dt-binding: cpu-topology: Move cpu-map to a
 common binding.
To:     Sudeep Holla <sudeep.holla@arm.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Anup Patel <anup@brainfault.org>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
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        Dmitriy Cherkasov <dmitriy@oss-tech.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>,
        Jeremy Linton <jeremy.linton@arm.com>,
        Juri Lelli <juri.lelli@arm.com>,
        "moderated list:ARM64 PORT (AARCH64 ARCHITECTURE)" 
        <linux-arm-kernel@lists.infradead.org>,
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        Mark Rutland <mark.rutland@arm.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will.deacon@arm.com>
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 <20181203165521.GB17883@e107155-lin>
 <f902086b-09e1-ad85-d191-137708f5b105@wdc.com>
 <20181203173306.GF17883@e107155-lin>
From:   Atish Patra <atish.patra@wdc.com>
Message-ID: <e983d74f-9671-a119-63a4-dd4e12fe0f96@wdc.com>
Date:   Mon, 3 Dec 2018 09:40:21 -0800
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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@arm.com>
>>>
>>>> Signed-off-by: Atish Patra <atish.patra@wdc.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
>