Fixing Santosh's email id as he switched employer .. On 26 November 2014 at 14:16, Viresh Kumar <viresh.kumar@xxxxxxxxxx> wrote: > 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 <viresh.kumar@xxxxxxxxxx> > --- > .../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 > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
