linux-kernel - Re: [PATCH V1 Resend 2/3] cpufreq: dt: Add generic platform-device creation support

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Date:	Fri, 1 Apr 2016 15:53:50 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	linaro-kernel@...ts.linaro.org, k.kozlowski@...sung.com,
	kgene.kim@...sung.com, heiko@...ech.de, linux-pm@...r.kernel.org,
	mmcclint@...eaurora.org, xf@...k-chips.com,
	Rafael Wysocki <rjw@...ysocki.net>,
	linux-kernel@...r.kernel.org, slash.tmp@...e.fr,
	rob.herring@...aro.org
Subject: Re: [PATCH V1 Resend 2/3] cpufreq: dt: Add generic platform-device
 creation support

Cc'ing Rob and Mason.

On 30-03-16, 09:53, Arnd Bergmann wrote:
> I think it should be something in the /cpus or the /opp_table hierarchy,
> not the root of the device tree, but other than that I don't care much
> whether it's a variation of the oppv2 compatible string or an additional
> property in any of the nodes.

So you mean for future DT files we can have something like this:

	cpus {
                compatible = "operation-points-v2";
		#address-cells = <1>;
		#size-cells = <0>;

		cpu@0 {
			compatible = "arm,cortex-a9";
			reg = <0>;
			next-level-cache = <&L2>;
			operating-points-v2 = <&cpu0_opp_table>;
		};
	};

	cpu0_opp_table: opp_table0 {
		opp@...0000000 {
			opp-hz = /bits/ 64 <1000000000>;
			opp-microvolt = <970000 975000 985000>;
			opp-microamp = <70000>;
			clock-latency-ns = <300000>;
			opp-suspend;
		};
		opp@...0000000 {
			opp-hz = /bits/ 64 <1100000000>;
			opp-microvolt = <980000 1000000 1010000>;
			opp-microamp = <80000>;
			clock-latency-ns = <310000>;
		};
	};
};


And the cpufreq-dt driver can match /cpus node's compatible string against
"operating-points-v2" and create a device at runtime ?

@Rob: Will that be acceptable to you? We are discussing (again) about how to
probe cpufreq-dt driver automatically for platforms :)

The cpus node doesn't have any 'compatible' property today, and I will be
required to add that in this case.

-- 
viresh