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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 8 Jul 2022 11:28:19 +0200
Message-ID: <CAMuHMdXUjmG9n3BuRAz_irkmHQbp=7SYxe5VEfOhMdT4D2JfwQ@mail.gmail.com>
Subject: Re: [RFC 2/4] arch-topology: add a default implementation of store_cpu_topology()
To:     Sudeep Holla <sudeep.holla@arm.com>
Cc:     Conor Dooley <Conor.Dooley@microchip.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        Palmer Dabbelt <palmer@rivosinc.com>,
        Albert Ou <aou@eecs.berkeley.edu>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Daire.McNamara@microchip.com,
        Niklas Cassel <niklas.cassel@wdc.com>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Zong Li <zong.li@sifive.com>,
        Emil Renner Berthing <kernel@esmil.dk>, hahnjo@hahnjo.de,
        Guo Ren <guoren@kernel.org>, Anup Patel <anup@brainfault.org>,
        Atish Patra <atishp@atishpatra.org>, changbin.du@intel.com,
        Heiko Stuebner <heiko@sntech.de>, philipp.tomsich@vrull.eu,
        Rob Herring <robh@kernel.org>, Marc Zyngier <maz@kernel.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        linux-riscv <linux-riscv@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Brice.Goglin@inria.fr
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Hi Sudeep,

On Fri, Jul 8, 2022 at 11:22 AM Sudeep Holla <sudeep.holla@arm.com> wrote:
> On Fri, Jul 08, 2022 at 08:35:57AM +0000, Conor.Dooley@microchip.com wrote:
> > On 08/07/2022 09:24, Sudeep Holla wrote:
> > > On Thu, Jul 07, 2022 at 11:04:35PM +0100, Conor Dooley wrote:
> > >> From: Conor Dooley <conor.dooley@microchip.com>
> > >>
> > >> RISC-V & arm64 both use an almost identical method of filling in
> > >> default vales for arch topology. Create a weakly defined default
> > >> implementation with the intent of migrating both archs to use it.
> > >>
> > >> Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
> > >> ---
> > >>   drivers/base/arch_topology.c  | 19 +++++++++++++++++++
> > >>   include/linux/arch_topology.h |  1 +
> > >>   2 files changed, 20 insertions(+)
> > >>
> > >> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> > >> index 441e14ac33a4..07e84c6ac5c2 100644
> > >> --- a/drivers/base/arch_topology.c
> > >> +++ b/drivers/base/arch_topology.c
> > >> @@ -765,6 +765,25 @@ void update_siblings_masks(unsigned int cpuid)
> > >>    }
> > >>   }
> > >>
> > >> +void __weak store_cpu_topology(unsigned int cpuid)
> >
> > Does using __weak here make sense to you?
> >
>
> I don't want any weak definition and arch to override as we know only
> arm64 and RISC-V are the only users and they are aligned to have same
> implementation. So weak definition doesn't make sense to me.
>
> > >
> > > I prefer to have this as default implementation. So just get the risc-v
> > > one pushed to upstream first(for v5.20) and get all the backports if required.
> > > Next cycle(i.e. v5.21), you can move both RISC-V and arm64.
> > >
> >
> > Yeah, that was my intention. I meant to label patch 1/4 as "PATCH"
> > and (2,3,4)/4 as RFC but forgot. I talked with Palmer about doing
> > the risc-v impl. and then migrate both on IRC & he seemed happy with
> > it.
> >
>
> Ah OK, good.
>
> > If you're okay with patch 1/4, I'll resubmit it as a standalone v2.
> >
>
> That would be great, thanks. You can most the code to move to generic from
> both arm64 and risc-v once we have this in v5.20-rc1

Why not ignore risc-v for now, and move the arm64 implementation to
the generic code for v5.20, so every arch will have it at once?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds