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

From: Sudeep Holla <sudeep.holla@arm.com>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	"Rafael J . Wysocki" <rjw@rjwysocki.net>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	"Raju P . L . S . S . S . N" <rplsssn@codeaurora.org>,
	Amit Kucheria <amit.kucheria@linaro.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Niklas Cassel <niklas.cassel@linaro.org>,
	Tony Lindgren <tony@atomide.com>,
	Kevin Hilman <khilman@kernel.org>,
	Lina Iyer <ilina@codeaurora.org>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Souvik Chakravarty <souvik.chakravarty@arm.com>,
	Linux PM <linux-pm@vger.kernel.org>,
	linux-arm-msm <linux-arm-msm@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Wei Xu <xuwei5@hisilicon.com>
Subject: Re: [PATCH 18/18] arm64: dts: hikey: Convert to the hierarchical CPU topology layout
Date: Thu, 18 Jul 2019 14:11:42 +0100	[thread overview]
Message-ID: <20190718131142.GA28633@e107155-lin> (raw)
In-Reply-To: <CAPDyKFpc26yL6rOnfwawL=eL649NsgTMrF1WrMHZv7AVd=3PCA@mail.gmail.com>

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@arm.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@hisilicon.com>
> > > Signed-off-by: Ulf Hansson <ulf.hansson@linaro.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