linux-kernel - Re: [PATCH v2 0/1] arm: topology: parse the topology from the dt

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Message-ID: <CAG7+-3OgN4Kx3Md1tOmqHDLs94DSv2puh=kA0oFMw+aZGnb3iw@mail.gmail.com>
Date:   Fri, 16 Apr 2021 19:04:38 +0800
From:   Ruifeng Zhang <ruifeng.zhang0110@...il.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        linux@...linux.org.uk, sudeep.holla@....com,
        Greg KH <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>, a.p.zijlstra@...llo.nl,
        mingo@...nel.org, ruifeng.zhang1@...soc.com, nianfu.bai@...soc.com,
        linux-arm-kernel@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/1] arm: topology: parse the topology from the dt

Dietmar Eggemann <dietmar.eggemann@....com> 于2021年4月16日周五 下午6:39写道：
>
> On 16/04/2021 11:32, Valentin Schneider wrote:
> > On 16/04/21 15:47, Ruifeng Zhang wrote:
> >> For more requirements, if all cores in one physical cluster, the
> >> {aff2} of all cores are the same value.
> >> i.e. the sc9863a,
> >> core0: 0000000081000000
> >> core1: 0000000081000100
> >> core2: 0000000081000200
> >> core3: 0000000081000300
> >> core4: 0000000081000400
> >> core5: 0000000081000500
> >> core6: 0000000081000600
> >> core7: 0000000081000700
> >>
> >> According to MPIDR all cores will parse to the one cluster, but it's
> >> the big.LITTLE system, it's need two logic cluster for schedule or
> >> cpufreq.
> >> So I think it's better to add the logic of parse topology from DT.
> >
> > Ah, so it's a slightly different issue, but still one that requires a
> > different means of specifying topology.
>
> I'm confused. Do you have the MT bit set to 1 then? So the issue that
> the mpidr handling in arm32's store_cpu_topology() is not correct does
> not exist?

I have reconfirmed it, the MT bit has been set to 1. I am sorry for
the previous messages.
The mpidr parse by store_cpu_topology is correct, at least for the sc9863a.

>
> With DynamIQ you have only *one* cluster, you should also be able to run
> your big.LITTLE system with only an MC sched domain.
>
> # cat /proc/schedstat
> cpu0 ....
> domain0 ff ... <- MC
> ...
>
> You can introduce a cpu-map to create what we called Phantom Domains in
> Android products.
>
> # cat /proc/schedstat
>
> cpu0 ....
> domain0 0f ... <- MC
> domain1 ff ... < DIE
>
> Is this what you need for your arm32 kernel system? Adding the
> possibility to parse cpu-map to create Phantom Domains?

Yes, I need parse DT cpu-map to create different Phantom Domains.
With it, the dts should be change to:
                cpu-map {
                        cluster0 {
                                core0 {
                                        cpu = <&CPU0>;
                                };
                                core1 {
                                        cpu = <&CPU1>;
                                };
                                core2 {
                                        cpu = <&CPU2>;
                                };
                                core3 {
                                        cpu = <&CPU3>;
                                };
                        };

                        cluster1 {
                                core0 {
                                        cpu = <&CPU4>;
                                };
                                core1 {
                                        cpu = <&CPU5>;
                                };
                                core2 {
                                        cpu = <&CPU6>;
                                };
                                core3 {
                                        cpu = <&CPU7>;
                                };
                        };
                };