From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: [RFC] cpufreq: Add "dvfs-method" binding to probe cpufreq drivers Date: Wed, 26 Nov 2014 14:16:12 +0530 Message-ID: <596a6d49f2b3e2837aa9a54a3e1249161d3c9265.1416991009.git.viresh.kumar@linaro.org> Return-path: Received: from mail-pa0-f53.google.com ([209.85.220.53]:36936 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbaKZIqY (ORCPT ); Wed, 26 Nov 2014 03:46:24 -0500 Received: by mail-pa0-f53.google.com with SMTP id kq14so2440676pab.40 for ; Wed, 26 Nov 2014 00:46:24 -0800 (PST) Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Rafael Wysocki Cc: linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org, Nishanth Menon , Sudeep Holla , Stephen Boyd , "devicetree@vger.kernel.org" , Santosh Shilimkar , Lorenzo Pieralisi , Arnd Bergmann , Mike Turquette , Rob Herring , Grant Likely , kesavan.abhilash@gmail.com, catalin.marinas@arm.com, k.chander@samsung.com, olof@lixom.net, ta.omasab@gmail.com, Viresh Kumar DT based cpufreq drivers doesn't require much support from platform code now a days as most of the stuff is moved behind generic APIs. Like clk APIs for changing clock rates, regulator APIs for changing voltages, etc. One of the bottleneck still left was how to select which cpufreq driver to probe for a given platform as there might be multiple drivers available. Traditionally, we used to create platform devices from machine specific code which binds with a cpufreq driver. And while we moved towards DT based device creation, these devices stayed as is. The problem is getting worse now as we have architectures now with Zero platform specific code. Forcefully these platforms have to create a new file in drivers/cpufreq/ to just add these platform devices in order to use the generic drivers like cpufreq-dt.c. This has been discussed again and again, but with no solution yet. Last it was discussed here: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256154.html This patch is an attempt towards getting the bindings. We only need to have one entry in cpus@cpu0 node which will match with drivers name. We can then add another file drivers/cpufreq/device_dt.c, which will add a platform device with the name it finds from cpus@cpu0 node and existing drivers will work without any change. Or something else if somebody have a better proposal. But lets fix the bindings first. Signed-off-by: Viresh Kumar --- .../devicetree/bindings/cpufreq/drivers.txt | 53 ++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 Documentation/devicetree/bindings/cpufreq/drivers.txt diff --git a/Documentation/devicetree/bindings/cpufreq/drivers.txt b/Documentation/devicetree/bindings/cpufreq/drivers.txt new file mode 100644 index 0000000..bd14917 --- /dev/null +++ b/Documentation/devicetree/bindings/cpufreq/drivers.txt @@ -0,0 +1,53 @@ +Binding to select which cpufreq driver to register + +It is a generic DT binding for selecting which cpufreq-driver to register for +any platform. + +The property listed below must be defined under node /cpus/cpu@0 node. We don't +support multiple CPUFreq driver currently for different cluster and so this +information isn't required to be present in CPUs of all clusters. + +Required properties: +- None + +Optional properties: +- dvfs-method: CPUFreq driver to probe. For example: "arm-bL-cpufreq-dt", + "cpufreq-dt", etc + +Examples: + +cpus { + #address-cells = <1>; + #size-cells = <0>; + + cpu@0 { + compatible = "arm,cortex-a9"; + reg = <0>; + next-level-cache = <&L2>; + operating-points = < + /* kHz uV */ + 792000 1100000 + 396000 950000 + 198000 850000 + >; + dvfs-method = "cpufreq-dt"; + }; + + cpu@1 { + compatible = "arm,cortex-a9"; + reg = <1>; + next-level-cache = <&L2>; + }; + + cpu@2 { + compatible = "arm,cortex-a9"; + reg = <2>; + next-level-cache = <&L2>; + }; + + cpu@3 { + compatible = "arm,cortex-a9"; + reg = <3>; + next-level-cache = <&L2>; + }; +}; -- 2.0.3.693.g996b0fd