linux-kernel - Re: [PATCH 00/18] ARM/ARM64: Support hierarchical CPU arrangement for PSCI

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Message-ID: <CAPDyKFqC8+Sv5WRhwOxqphAt8tb_PDisy13Miz5e-PajvwS1ew@mail.gmail.com>
Date:   Mon, 10 Jun 2019 20:57:07 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "Raju P . L . S . S . S . N" <rplsssn@...eaurora.org>,
        Amit Kucheria <amit.kucheria@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Niklas Cassel <niklas.cassel@...aro.org>,
        Tony Lindgren <tony@...mide.com>,
        Kevin Hilman <khilman@...nel.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Souvik Chakravarty <souvik.chakravarty@....com>,
        Linux PM <linux-pm@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/18] ARM/ARM64: Support hierarchical CPU arrangement for PSCI

On Mon, 10 Jun 2019 at 19:16, Lorenzo Pieralisi
<lorenzo.pieralisi@....com> wrote:
>
> On Mon, Jun 10, 2019 at 05:54:39PM +0200, Ulf Hansson wrote:
>
> [...]
>
> > My summary from the earlier ones, is that because the PSCI spec
> > includes support for OSI, we should also support it in the kernel (and
> > ATF). In a discussion offlist, Lorenzo agreed that it's okay to add,
> > without an apple to apple comparison. Maybe Lorenzo can fill in and
> > state this publicly, to save us all some time?
>
> The comparison should have been made before even requesting PSCI OSI
> mode changes to the specifications, so we have a chip on our shoulders
> anyway.
>
> We will enable PSCI OSI but that's not where the problem lies, enabling
> PSCI OSI from a firmware perspective should take 10 lines of code,
> not:

Thanks for confirming!

>
>  drivers/firmware/psci/Makefile                |   2 +-
>  drivers/firmware/psci/psci.c                  | 219 ++++++++--
>  drivers/firmware/psci/psci.h                  |  29 ++
>  drivers/firmware/psci/psci_pm_domain.c        | 403 ++++++++++++++++++
>
> I have some concerns about these changes that I will state in the
> relevant patches.

Most of the above changes isn't for solely for OSI, but to support a
hierarchical topology described in the PSCI DT layout. This is for
example needed when other resources shares the same power rail as the
CPU cluster.

In other words, the series is orthogonal to whether OSI or PC mode is
used for PSCI, just to make that clear. BTW, this is what you
requested me to change into, a while ago.

>
> > My final point in regards to the OSI mode support, it's a minor part
> > of the series. I don't see how that should hurt from a maintenance
> > point of view, or perhaps I am wrong? In any case, I offer my help
> > with review/maintenance in any form as you may see need/fit.
>
> I will go through the series but most of this code should move
> to core PM code, it has nothing to do with PSCI.

I am looking forward to your review - and for sure, I am open to suggestions!

>
> BTW, apologies for the delay, I was away.
>
> Thanks,
> Lorenzo

Kind regards
Uffe