linux-kernel - Re: [PATCH] arm64: acpi: reenumerate topology ids

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Date:   Fri, 29 Jun 2018 11:29:27 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Andrew Jones <drjones@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        jeremy.linton@....com, ard.biesheuvel@...aro.org,
        shunyong.yang@...-semitech.com, yu.zheng@...-semitech.com,
        catalin.marinas@....com, will.deacon@....com
Subject: Re: [PATCH] arm64: acpi: reenumerate topology ids

On Thu, Jun 28, 2018 at 07:32:43PM +0200, Andrew Jones wrote:
> On Thu, Jun 28, 2018 at 05:30:51PM +0100, Sudeep Holla wrote:
> > I am not sure if we can ever guarantee that DT and ACPI will get the
> > same ids whatever counter we use as it depends on the order presented in
> > the firmware(DT or ACPI). So I am not for generating ids for core and
> > threads in that way.
>
> I don't believe we have to guarantee that the exact (package,core,thread)
> triplet describing a PE with DT matches ACPI. We just need to guarantee
> that each triplet we select properly puts a PE in the same group as its
> peers. So, as long as we keep the grouping described by DT or ACPI, then
> the (package,core,thread) IDs assigned are pretty arbitrary.
>

If that's the requirement, we already do that. The IDs are just too
arbitrary :)

> I could change the commit message to state we can generate IDs *like*
> DT does (i.e. with counters), even if they may not result in identical
> triplet to PE mappings.
>

Why we need to make it *like DT* ?

> >
> > So I would like to keep it simple and just have this counters for
> > package ids as demonstrated in Shunyong's patch.
> >
>
> If we don't also handle cores when there are threads, then the cores
> will also end up having weird IDs.
>

Yes, but if PPTT says it has valid ID, I would prefer that over DT like
generated.

--
Regards,
Sudeep