linux-kernel - Re: [RFC PATCH v2 1/2] topology: Represent clusters of CPUs within a die.

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Message-ID: <20201202095556.cke6caza2hpw3cmn@bogus>
Date:   Wed, 2 Dec 2020 09:55:56 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Barry Song <song.bao.hua@...ilicon.com>
Cc:     Valentin Schneider <valentin.schneider@....com>,
        catalin.marinas@....com, will@...nel.org, rjw@...ysocki.net,
        lenb@...nel.org, gregkh@...uxfoundation.org,
        Jonathan.Cameron@...wei.com, mingo@...hat.com,
        peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        mark.rutland@....com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linuxarm@...wei.com, xuwei5@...wei.com, prime.zeng@...ilicon.com,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [RFC PATCH v2 1/2] topology: Represent clusters of CPUs within a
 die.

On Tue, Dec 01, 2020 at 04:03:46PM +0000, Valentin Schneider wrote:
> 
> On 01/12/20 02:59, Barry Song wrote:
> > Currently the ID provided is the offset of the Processor
> > Hierarchy Nodes Structure within PPTT.  Whilst this is unique
> > it is not terribly elegant so alternative suggestions welcome.
> >

I had already mentioned that you need to fix the firmware/PPTT on your
platform. If you fill only mandatory fields, then yes this is optional
and we resort to use offset as unique number in the kernel.

>
> Skimming through the spec, this sounds like something the ID structure
> (Type 2) could be used for. However in v1 Jonathan and Sudeep talked about
> UID's / DSDT, any news on that?
>

FYI, type 2 is for SoC identification which is being deprecated(still
need to check if that progressed and made to the official release yet)
in favour of Arm SMCCC v1.2 SOC_ID. Anyways it is irrelevant in this
context. They need to use UIDs and mark the corresponding flag as valid
for OSPM/kernel to use it.

> > Note that arm64 / ACPI does not provide any means of identifying
> > a die level in the topology but that may be unrelate to the cluster
> > level.
> >

May need spec extension if there are no ways to identify the same.

-- 
Regards,
Sudeep