linux-kernel - Re: [PATCH v2 1/2] arm64: topology: move store_cpu

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Message-ID: <20220711100204.bj3r3g6xs577kuul@bogus>
Date:   Mon, 11 Jul 2022 11:02:04 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Conor.Dooley@...rochip.com
Cc:     paul.walmsley@...ive.com, palmer@...belt.com, palmer@...osinc.com,
        aou@...s.berkeley.edu, catalin.marinas@....com, will@...nel.org,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        linux@...linux.org.uk, arnd@...db.de, Daire.McNamara@...rochip.com,
        niklas.cassel@....com, damien.lemoal@...nsource.wdc.com,
        geert@...ux-m68k.org, zong.li@...ive.com, kernel@...il.dk,
        hahnjo@...njo.de, guoren@...nel.org, anup@...infault.org,
        atishp@...shpatra.org, heiko@...ech.de, philipp.tomsich@...ll.eu,
        robh@...nel.org, maz@...nel.org, viresh.kumar@...aro.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, Brice.Goglin@...ia.fr
Subject: Re: [PATCH v2 1/2] arm64: topology: move store_cpu_topology() to
 shared code

On Sat, Jul 09, 2022 at 12:58:57PM +0000, Conor.Dooley@...rochip.com wrote:
> Looking at the arm32 implementation - it appears to be mostly the sort of MPIDR
> stuff that was removed from the arm64 implementation in 3102bc0e6ac7 ("arm64:
> topology: Stop using MPIDR for topology information"). Could arm32 benefit from
> the same shared implemenation too, or is usage of MPIDR only invalid for arm64?

I don't recall all the details but IIRC there are parts if arch_topology
that are ARM64/RISC-V only. ARM32 doesn't use it as it may break old
platforms. Some of the functions that still arm32 specific are retained
in arch/arm

> The other difference is a call to update_cpu_capacity() in the arm32
> implementation. Could that be moved to smp_store_cpu_info() which is the only
> callsite of store_cpu_topology()?
>

No please, leave arm32 as is. It was done for a reason like that and it
help to not break some of the old 32-by platforms.

> Either way, will respin a v3 that doesn't break the arm32 build when
> CONFIG_GENERIC_ARCH_TOPOLOGY is enabled :)
>

Thanks.

-- 
Regards,
Sudeep