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 09:23:42 -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 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 


Regards,
Atish
> The reason I ask is people tend to copy from existing DT or examples
> like here and so want to make sure if it can be kept as generic as
> possible in the example. Just my opinion and I am fine if you want to
> keep it as is, thought of checking the intentions here.
> 



> --
> Regards,
> Sudeep
>