linux-kernel - Re: [PATCH v2 06/16] arm64: dts: mt7622: add cpufreq related device nodes

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Message-ID: <20180207061837.GM28462@vireshk-i7>
Date:   Wed, 7 Feb 2018 11:48:37 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Sean Wang <sean.wang@...iatek.com>
Cc:     robh+dt@...nel.org, matthias.bgg@...il.com, mark.rutland@....com,
        devicetree@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 06/16] arm64: dts: mt7622: add cpufreq related device
 nodes

On 07-02-18, 14:16, Sean Wang wrote:
> On Wed, 2018-02-07 at 09:03 +0530, Viresh Kumar wrote:
> > On 06-02-18, 17:52, sean.wang@...iatek.com wrote:
> > >  	cpus {
> > >  		#address-cells = <2>;
> > >  		#size-cells = <0>;
> > > @@ -26,6 +70,10 @@
> > >  			device_type = "cpu";
> > >  			compatible = "arm,cortex-a53", "arm,armv8";
> > >  			reg = <0x0 0x0>;
> > > +			clocks = <&infracfg CLK_INFRA_MUX1_SEL>,
> > > +				 <&apmixedsys CLK_APMIXED_MAIN_CORE_EN>;
> > > +			clock-names = "cpu", "intermediate";
> > > +			operating-points-v2 = <&cpu_opp_table>;
> > >  			enable-method = "psci";
> > >  			clock-frequency = <1300000000>;
> > >  		};
> > > @@ -34,6 +82,7 @@
> > >  			device_type = "cpu";
> > >  			compatible = "arm,cortex-a53", "arm,armv8";
> > >  			reg = <0x0 0x1>;
> > > +			operating-points-v2 = <&cpu_opp_table>;
> > >  			enable-method = "psci";
> > >  			clock-frequency = <1300000000>;
> > >  		};
> > 
> > Sorry for not picking this earlier, but you should probably add the same clock
> > related properties for both cpu nodes here. Things will break if CPU1 is used by
> > the cpufreq core to bring the cpufreq policy online.
> > 
> > This can happen if cpufreq driver is a module, CPU0 is hotplugged out and then
> > the cpufreq driver is inserted.
> > 
> 
> mt7622 cpu0 does not support hotplug. do I still need to add same clock
> related properties for both cpu nodes here?

Normally we should always add these properties to all the CPUs, as that's the
real scenario hardware configuration wise.

But I am not sure if something else will break if you don't provide clocks in
CPU1.

@Rob @Mark: What do you suggest ?

-- 
viresh