linux-kernel - Re: [PATCH v2 0/3] pmdomain: ti_sci: collect and send low-power mode constraints

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Message-ID: <CAPDyKFrBSHRmP+CFd7xWXnN6LXKaAtihYv22b60wYsgSShCD+g@mail.gmail.com>
Date: Fri, 6 Sep 2024 11:00:09 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Kevin Hilman <khilman@...libre.com>
Cc: linux-pm@...r.kernel.org, Nishanth Menon <nm@...com>, Vibhore Vardhan <vibhore@...com>, 
	Dhruva Gole <d-gole@...com>, Akashdeep Kaur <a-kaur@...com>, Sebin Francis <sebin.francis@...com>, 
	Markus Schneider-Pargmann <msp@...libre.com>, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] pmdomain: ti_sci: collect and send low-power mode constraints

On Fri, 6 Sept 2024 at 00:07, Kevin Hilman <khilman@...libre.com> wrote:
>
> Ulf Hansson <ulf.hansson@...aro.org> writes:
>
> > On Tue, 20 Aug 2024 at 02:00, Kevin Hilman <khilman@...libre.com> wrote:
> >>
> >> The latest (10.x) version of the firmware for the PM co-processor (aka
> >> device manager, or DM) adds support for a "managed" mode, where the DM
> >> firmware will select the specific low power state which is entered
> >> when Linux requests a system-wide suspend.
> >>
> >> In this mode, the DM will always attempt the deepest low-power state
> >> available for the SoC.
> >>
> >> However, Linux (or OSes running on other cores) may want to constrain
> >> the DM for certain use cases.  For example, the deepest state may have
> >> a wakeup/resume latency that is too long for certain use cases.  Or,
> >> some wakeup-capable devices may potentially be powered off in deep
> >> low-power states, but if one of those devices is enabled as a wakeup
> >> source, it should not be powered off.
> >>
> >> These kinds of constraints are are already known in Linux by the use
> >> of existing APIs such as per-device PM QoS and device wakeup APIs, but
> >> now we need to communicate these constraints to the DM.
> >>
> >> For TI SoCs with TI SCI support, all DM-managed devices will be
> >> connected to a TI SCI PM domain.  So the goal of this series is to use
> >> the PM domain driver for TI SCI devices to collect constraints, and
> >> communicate them to the DM via the new TI SCI APIs.
> >>
> >> This is all managed by TI SCI PM domain code.  No new APIs are needed
> >> by Linux drivers.  Any device that is managed by TI SCI will be
> >> checked for QoS constraints or wakeup capability and the constraints
> >> will be collected and sent to the DM.
> >>
> >> This series depends on the support for the new TI SCI APIs (v10) and
> >> was also tested with this series to update 8250_omap serial support
> >> for AM62x[2].
> >>
> >> [1] https://lore.kernel.org/all/20240801195422.2296347-1-msp@baylibre.com
> >> [2] https://lore.kernel.org/all/20240807141227.1093006-1-msp@baylibre.com/
> >>
> >> Signed-off-by: Kevin Hilman <khilman@...libre.com>
> >> ---
> >> Changes in v2:
> >>
> >> - To simplify this version a bit, drop the pmdomain ->power_off()
> >>   changes.  Constraints only sent during ->suspend() path.  The pmdomain
> >>   path was an optimization that may be added back later.
> >> - With the above simplification, drop the extra state variables that
> >>   had been added to keep track of constraint status.
> >> - Link to v1: https://lore.kernel.org/r/20240805-lpm-v6-10-constraints-pmdomain-v1-0-d186b68ded4c@baylibre.com
> >>
> >> ---
> >> Kevin Hilman (3):
> >>       pmdomain: ti_sci: add per-device latency constraint management
> >>       pmdomain: ti_sci: add wakeup constraint management
> >>       pmdomain: ti_sci: handle wake IRQs for IO daisy chain wakeups
> >>
> >>  drivers/pmdomain/ti/ti_sci_pm_domains.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 76 insertions(+)
> >> ---
> >> base-commit: ad7eb1b6b92ee0c959a0a6ae846ddadd7a79ea64
> >> change-id: 20240802-lpm-v6-10-constraints-pmdomain-f33df5aef449
> >>
> >> Best regards,
> >> --
> >> Kevin Hilman <khilman@...libre.com>
> >
> > Besides a couple of minor things that I have commented on for each
> > patch, this looks okay to me!
> >
> > Taking into account the other series that this depends on, what is the
> > best merging strategy? Is it safe for me to take it through my
> > pmdomain tree?
>
>
> That other series should be merged shortly, so I will check with
> Nishanth (on cc) if he can create an immutable branch/tag that you could
> use in your tree.
>
> It has a build-time dependency on that other series, so I think this is
> the best way.
>
> Alternatively, if you don't expect this to clash with other changes in
> your tree, with your ack/reviewed-by, Nishanth could merge this series
> via his tree and we could avoid the cross-tree shuffle.

At the moment there shouldn't be any clashes I think. Let's use
Nishanth's tree and see how it goes.

I will ack/review the patches when they are ready.

Kind regards
Uffe