linux-kernel - Re: [PATCH 07/18] drivers: firmware: psci: Prepare to use OS initiated suspend mode

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Message-ID: <20190607151716.GF15577@e107155-lin>
Date:   Fri, 7 Jun 2019 16:17:16 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Mark Rutland <mark.rutland@....com>,
        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>,
        Bjorn Andersson <bjorn.andersson@...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>,
        Sudeep Holla <sudeep.holla@....com>, linux-pm@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Lina Iyer <lina.iyer@...aro.org>
Subject: Re: [PATCH 07/18] drivers: firmware: psci: Prepare to use OS
 initiated suspend mode

On Mon, May 13, 2019 at 09:22:49PM +0200, Ulf Hansson wrote:
> The per CPU variable psci_power_state, contains an array of fixed values,
> which reflects the corresponding arm,psci-suspend-param parsed from DT, for
> each of the available CPU idle states.
>
> This isn't sufficient when using the hierarchical CPU topology in DT in
> combination with having PSCI OS initiated (OSI) mode enabled. More
> precisely, in OSI mode, Linux is responsible of telling the PSCI FW what
> idle state the cluster (a group of CPUs) should enter, while in PSCI
> Platform Coordinated (PC) mode, each CPU independently votes for an idle
> state of the cluster.
>
> For this reason, let's introduce an additional per CPU variable called
> domain_state and implement two helper functions to read/write its values.
> Following patches, which implements PM domain support for PSCI, will use
> the domain_state variable and set it to corresponding bits that represents
> the selected idle state for the cluster.
>
> Finally, in psci_cpu_suspend_enter() and psci_suspend_finisher(), let's
> take into account the values in the domain_state, as to get the complete
> suspend parameter.
>

I understand it was split to ease review, but this patch also does
nothing as domain_state = 0 always. I was trying hard to find where it's
set, but I assume it will be done in later patches. Again may be this
can be squashed into the first caller of psci_set_domain_state

--
Regards,
Sudeep