linux-kernel - Re: [PATCH v2 0/3] PM / Domains: Add power on/off notifiers for genpd

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Date:   Mon, 28 Sep 2020 13:56:34 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lina Iyer <ilina@...eaurora.org>,
        Lukasz Luba <lukasz.luba@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/3] PM / Domains: Add power on/off notifiers for genpd

Rafael,

On Thu, 24 Sep 2020 at 13:06, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>
> Changes in v2:
>         - Improved error handling in patch3.
>
> A device may have specific HW constraints that must be obeyed to, before its
> corresponding PM domain (genpd) can be powered off - and vice verse at power
> on. These constraints can't be managed through the regular runtime PM based
> deployment for a device, because the access pattern for it, isn't always
> request based. In other words, using the runtime PM callbacks to deal with the
> constraints doesn't work for these cases.
>
> For these reasons, this series introduces a power on/off notification mechanism
> to genpd. To add/remove a notifier for a device, the device must already have
> been attached to the genpd, which also means that it needs to be a part of the
> PM domain topology.
>
> The intent is to allow these genpd power on/off notifiers to replace the need
> for the existing CPU_CLUSTER_PM_ENTER|EXIT notifiers. For example, those would
> otherwise be needed in psci_pd_power_off() in cpuidle-psci-domain.c, when
> powering off the CPU cluster.
>
> Another series that enables drivers/soc/qcom/rpmh-rsc.c to make use of the new
> genpd on/off notifiers, are soon to be posted. However, I would appreciate any
> feedback on the approach taken, even before that series hits LKML.
>
> Kind regards
> Ulf Hansson
>
>
> Ulf Hansson (3):
>   PM / Domains: Rename power state enums for genpd
>   PM / Domains: Allow to abort power off when no ->power_off() callback
>   PM / Domains: Add support for PM domain on/off notifiers for genpd
>
>  drivers/base/power/domain.c | 187 +++++++++++++++++++++++++++++-------
>  include/linux/pm_domain.h   |  19 +++-
>  2 files changed, 171 insertions(+), 35 deletions(-)
>
> --
> 2.25.1
>

I will need to iterate patch 3, potentially even a couple of more times.

As I expect patch 1 and patch2 to not get changed, may I suggest that
you pick up those so we can move focus to patch3?

Kind regards
Uffe