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

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Date:   Mon, 10 Jun 2019 18:16:08 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
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, 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:

 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.

> 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.

BTW, apologies for the delay, I was away.

Thanks,
Lorenzo