linux-kernel - Re: [PATCH 18/18] arm64: dts: hikey: Convert to the hierarchical CPU topology layout

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Date:   Thu, 18 Jul 2019 14:11:42 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Raju P . L . S . S . S . N" <rplsssn@...eaurora.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Souvik Chakravarty <souvik.chakravarty@....com>,
        Linux PM <linux-pm@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Wei Xu <xuwei5@...ilicon.com>
Subject: Re: [PATCH 18/18] arm64: dts: hikey: Convert to the hierarchical CPU
 topology layout

On Thu, Jul 18, 2019 at 12:48:14PM +0200, Ulf Hansson wrote:
> On Tue, 16 Jul 2019 at 16:47, Sudeep Holla <sudeep.holla@....com> wrote:
> >
> > On Mon, May 13, 2019 at 09:23:00PM +0200, Ulf Hansson wrote:
> > > To enable the OS to manage last-man standing activities for a CPU, while an
> > > idle state for a group of CPUs is selected, let's convert the Hikey
> > > platform into using the hierarchical CPU topology layout.
> > >
> > > Cc: Wei Xu <xuwei5@...ilicon.com>
> > > Signed-off-by: Ulf Hansson <ulf.hansson@...aro.org>
> > > ---
> > >
> > > Changes:
> > >       - None.
> > >
> > > ---
> > >  arch/arm64/boot/dts/hisilicon/hi6220.dtsi | 87 ++++++++++++++++++++---
> > >  1 file changed, 76 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/arch/arm64/boot/dts/hisilicon/hi6220.dtsi b/arch/arm64/boot/dts/hisilicon/hi6220.dtsi
> > > index 108e2a4227f6..36ff460f428f 100644
> > > --- a/arch/arm64/boot/dts/hisilicon/hi6220.dtsi
> > > +++ b/arch/arm64/boot/dts/hisilicon/hi6220.dtsi
> > >       cpus {
> >
> > [...]
> >
> > > @@ -70,9 +128,8 @@
> > >                       };
> > >
> > >                       CLUSTER_SLEEP: cluster-sleep {
> > > -                             compatible = "arm,idle-state";
> > > -                             local-timer-stop;
> > > -                             arm,psci-suspend-param = <0x1010000>;
> > > +                             compatible = "domain-idle-state";
> > > +                             arm,psci-suspend-param = <0x1000000>;
> > >                               entry-latency-us = <1000>;
> > >                               exit-latency-us = <700>;
> > >                               min-residency-us = <2700>;
> >
> > Again this must be original format and as per PSCI spec, your patch
> > changes this cluster sleep state into cluster retention state which I
> > think is not what you intended.
>
> If the hierarchical topology is used, the parameter for cluster states
> are ORed with the deepest idle state for the CPU.
>
> CPU_SLEEP: 0x0010000
> CLUSTER_SLEEP: 0x1000000
>
> After the ORed operation
> CLUSTER_SLEEP: 0x1010000
>
> So, this indeed works as expected.
>

Yes, it works. But we are not XOR-ing so what's wrong in keeping the
StateType as required and be compliant to specification. Why do we need
to make the state param on it's own non-complaint.

What's wrong in retaining CLUSTER_SLEEP as 0x1010000 so that it reflects
the state level and type correctly on it's own ?

> However, are you saying that ORing the state parameters like above has
> other problems? I am reading your other replies...
>

Yes OR-ing may have other problems but the point I made here was more on
PSCI spec compliance for each suspend parameter values independently.

--
Regards,
Sudeep