linux-kernel - Re: [PATCH v6 00/21] Introduce power-off+restart call chain API

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Message-ID: <de2cbd2a-8d0d-8678-e514-b153d04546cc@gmx.de>
Date:   Wed, 16 Feb 2022 21:30:26 +0100
From:   Helge Deller <deller@....de>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Dmitry Osipenko <digetx@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
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        Lee Jones <lee.jones@...aro.org>,
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        "K . C . Kuen-Chern Lin" <kclin@...estech.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Subject: Re: [PATCH v6 00/21] Introduce power-off+restart call chain API

On 2/16/22 13:25, Rafael J. Wysocki wrote:
> On Tue, Feb 15, 2022 at 11:00 PM Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> 31.01.2022 02:36, Dmitry Osipenko пишет:
>>> Problem
>>> -------
>>>
>>> SoC devices require power-off call chaining functionality from kernel.
>>> We have a widely used restart chaining provided by restart notifier API,
>>> but nothing for power-off.
>>>
>>> Solution
>>> --------
>>>
>>> Introduce new API that provides both restart and power-off call chains.
>>>
>>> Why combine restart with power-off? Because drivers often do both.
>>> More practical to have API that provides both under the same roof.
>>>
>>> The new API is designed with simplicity and extensibility in mind.
>>> It's built upon the existing restart and reboot APIs. The simplicity
>>> is in new helper functions that are convenient for drivers. The
>>> extensibility is in the design that doesn't hardcode callback
>>> arguments, making easy to add new parameters and remove old.
>>>
>>> This is a third attempt to introduce the new API. First was made by
>>> Guenter Roeck back in 2014, second was made by Thierry Reding in 2017.
>>> In fact the work didn't stop and recently arm_pm_restart() was removed
>>> from v5.14 kernel, which was a part of preparatory work started by
>>> Guenter Roeck. I took into account experience and ideas from the
>>> previous attempts, extended and polished them.
>>
>>
>> Rafael and all, do you see anything critical that needs to be improved
>> in this v6?
>>
>> Will be great if you could take this patchset via the power tree if it
>> looks okay, or give an ack.
>
> I need some more time for this, sorry.
>
> I'm a bit concerned about seeing no response to this set from anyone.
>
> It looks like multiple platforms may be affected by it in principle,
> so doesn't anyone care?

I did looked into the whole patch set after applying it locally.

While I agree a new combined API is good, and the beginning looked promising,
after some time I started to ask myself if the whole infrastructure might
be a little overdesigned.

Anyway, I tested it and it works for me on parisc.
And it's probably better than what we have today.

Helge