linux-kernel - Re: [PATCH] arm64: dts: qcom: qcs404: Add PSCI cpuidle support

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Date:   Wed, 8 May 2019 16:56:00 +0200
From:   Niklas Cassel <niklas.cassel@...aro.org>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        David Brown <david.brown@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jorge Ramirez-Ortiz <jorge.ramirez-ortiz@...aro.org>,
        Lina Iyer <lina.iyer@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: dts: qcom: qcs404: Add PSCI cpuidle support

On Wed, May 08, 2019 at 02:48:19AM +0530, Amit Kucheria wrote:
> On Tue, May 7, 2019 at 1:01 AM Niklas Cassel <niklas.cassel@...aro.org> wrote:
> >
> > Add device bindings for CPUs to suspend using PSCI as the enable-method.
> >
> > Signed-off-by: Niklas Cassel <niklas.cassel@...aro.org>
> > ---
> >  arch/arm64/boot/dts/qcom/qcs404.dtsi | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/qcs404.dtsi b/arch/arm64/boot/dts/qcom/qcs404.dtsi
> > index ffedf9640af7..f9db9f3ee10c 100644
> > --- a/arch/arm64/boot/dts/qcom/qcs404.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/qcs404.dtsi
> > @@ -31,6 +31,7 @@
> >                         reg = <0x100>;
> >                         enable-method = "psci";
> >                         next-level-cache = <&L2_0>;
> > +                       cpu-idle-states = <&CPU_PC>;
> >                 };
> >
> >                 CPU1: cpu@101 {
> > @@ -39,6 +40,7 @@
> >                         reg = <0x101>;
> >                         enable-method = "psci";
> >                         next-level-cache = <&L2_0>;
> > +                       cpu-idle-states = <&CPU_PC>;
> >                 };
> >
> >                 CPU2: cpu@102 {
> > @@ -47,6 +49,7 @@
> >                         reg = <0x102>;
> >                         enable-method = "psci";
> >                         next-level-cache = <&L2_0>;
> > +                       cpu-idle-states = <&CPU_PC>;
> >                 };
> >
> >                 CPU3: cpu@103 {
> > @@ -55,12 +58,24 @@
> >                         reg = <0x103>;
> >                         enable-method = "psci";
> >                         next-level-cache = <&L2_0>;
> > +                       cpu-idle-states = <&CPU_PC>;
> >                 };
> >
> >                 L2_0: l2-cache {
> >                         compatible = "cache";
> >                         cache-level = <2>;
> >                 };
> > +
> > +               idle-states {
> 
> entry-method="psci" property goes here. I have a patch fixing it for 410c ;-)
> 
> I don't think the psci_cpuidle_ops will even get called without this.

Hello Amit,

I added debug prints in psci_cpu_suspend_enter() and arm_cpuidle_suspend()
when verifying this patch, and psci_cpu_suspend_enter() is indeed called,
with the correct psci suspend parameter.

The output from:
grep "" /sys/bus/cpu/devices/cpu0/cpuidle/state?/*
also looks sane.

However, if 'entry-method="psci"' is required according to the DT binding,
perhaps you can send a 2/2 series that fixes both this patch and msm8916 ?

> Did you see any changes in consumption with this patch? I was trying
> to measure that before sending this out.

I don't know of any way to measure the power consumption on this board,
so no, I haven't been able to verify that the firmware actually does
the right thing here.


Kind regards,
Niklas

> 
> > +                       CPU_PC: pc {
> > +                               compatible = "arm,idle-state";
> > +                               arm,psci-suspend-param = <0x40000003>;
> > +                               entry-latency-us = <125>;
> > +                               exit-latency-us = <180>;
> > +                               min-residency-us = <595>;
> > +                               local-timer-stop;
> > +                       };
> > +               };
> >         };
> >
> >         firmware {
> > --
> > 2.21.0
> >