linux-kernel - Re: [PATCH v3 0/6] PM: QoS: Introduce a CPU system wakeup QoS limit for s2idle

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Message-ID: <CAPDyKFqAOdezBdBHu2WpQKJB2tpasWyHToMR4QJn+-pW3Ndx+w@mail.gmail.com>
Date: Tue, 25 Nov 2025 12:31:29 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: linux-pm@...r.kernel.org, Vincent Guittot <vincent.guittot@...aro.org>, 
	Peter Zijlstra <peterz@...radead.org>, Kevin Hilman <khilman@...libre.com>, 
	Pavel Machek <pavel@...nel.org>, Len Brown <len.brown@...el.com>, 
	Daniel Lezcano <daniel.lezcano@...aro.org>, Maulik Shah <quic_mkshah@...cinc.com>, 
	Prasad Sodagudi <psodagud@...cinc.com>, Dhruva Gole <d-gole@...com>, 
	Deepti Jaggi <quic_djaggi@...cinc.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/6] PM: QoS: Introduce a CPU system wakeup QoS limit
 for s2idle

On Mon, 24 Nov 2025 at 19:27, Rafael J. Wysocki <rafael@...nel.org> wrote:
>
> On Fri, Nov 21, 2025 at 11:03 AM Ulf Hansson <ulf.hansson@...aro.org> wrote:
> >
> > Changes in v3:
> >         - Take new the new QoS limit into account for cpuidle too (Rafael).
> >         - Add a new Kconfig for the new QoS interface (Rafael)
> >         - Improved the documentation (Dhruva)
> >         - Clarified commit messages and added acks.
> >
> > Changes in v2:
> >         - Limit the new QoS to CPUs  and make some corresponding renaming of the
> >         functions along with name of the device node for user space.
> >         - Make sure we deal with the failure/error path correctly when there are
> >         no state available for s2idle.
> >         - Add documentation.
> >
> > Some platforms supports multiple low power states for CPUs that can be used
> > when entering system-wide suspend and s2idle in particular. Currently we are
> > always selecting the deepest possible state for the CPUs, which can break the
> > system wakeup latency constraint that may be required for a use case.
> >
> > Therefore, this series suggests to introduce a new interface for user space,
> > allowing us to specify the CPU system wakeup QoS limit. The QoS limit is then
> > taken into account when selecting a suitable low power state for s2idle/cpuidle.
> >
> > Kind regards
> > Ulf Hansson
> >
> >
> > Ulf Hansson (6):
> >   PM: QoS: Introduce a CPU system wakeup QoS limit
> >   pmdomain: Respect the CPU system wakeup QoS limit for s2idle
> >   pmdomain: Respect the CPU system wakeup QoS limit for cpuidle
> >   sched: idle: Respect the CPU system wakeup QoS limit for s2idle
> >   cpuidle: Respect the CPU system wakeup QoS limit for cpuidle
> >   Documentation: power/cpuidle: Document the CPU system wakeup latency
> >     QoS
> >
> >  Documentation/admin-guide/pm/cpuidle.rst |   9 ++
> >  Documentation/power/pm_qos_interface.rst |   9 +-
> >  drivers/cpuidle/cpuidle.c                |  12 +--
> >  drivers/cpuidle/governor.c               |   4 +
> >  drivers/pmdomain/core.c                  |  10 ++-
> >  drivers/pmdomain/governor.c              |  33 ++++++-
> >  include/linux/cpuidle.h                  |   6 +-
> >  include/linux/pm_domain.h                |   1 +
> >  include/linux/pm_qos.h                   |   9 ++
> >  kernel/power/Kconfig                     |   4 +
> >  kernel/power/qos.c                       | 106 +++++++++++++++++++++++
> >  kernel/sched/idle.c                      |  12 +--
> >  12 files changed, 196 insertions(+), 19 deletions(-)
> >
> > --
>
> It looks good to me now.

Thanks!

>
> Do you want me to pick it up or do you want to route it differently?

I think you can pick this up via your tree. As I have some changes
queued via my pmdomain tree for the genpd governor, I asked git to
merge our branches (with this series applied to your tree) and it
seems to be working fine.

To address Dhruva's minor comments I just posted a new version, please
queue it via your tree.

Kind regards
Uffe