On Tue, May 10, 2022 at 1:33 AM Dmitry Osipenko
wrote:
>
> 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 call chains support for all restart and
> power-off modes. The new API is designed with simplicity and extensibility
> in mind.
>
> 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.
>
> Adoption plan
> -
>
> This patchset introduces the new API. It also converts multiple drivers
> and arch code to the new API to demonstrate how it all looks in practice,
> removing the pm_power_off_prepare global variable.
>
> The plan is:
>
> 1. Merge the new API and convert arch code to use do_kernel_power_off().
>For now the new API will co-exist with the older API.
>
> 2. Convert all drivers and platform code to the new API.
>
> 3. Remove obsoleted pm_power_off and pm_power_off_prepare variables.
>
> Results
> ---
>
> 1. Devices can be powered off properly.
>
> 2. Global variables are removed from drivers.
>
> 3. Global pm_power_off and pm_power_off_prepare callback variables are
> removed once all users are converted to the new API. The latter callback
> is removed by patch #24 of this series.
>
> 4. Ambiguous call chain ordering is prohibited for non-default priorities.
>
> Changelog:
>
> v8: - Reworked sys-off handler like was suggested by Rafael Wysocki in
> the comments to v7.
>
> - The struct sys-off handler now is private to kernel/reboot.c and
> new API is simplified.
>
> - There is a single sys-off API function for all handler types.
> Users shall pass the required sys-off mode type (restart, power-off
> and etc).
>
> - There is single struct sys_off_data callback argument for all
> handler modes.
>
> - User's callback now must return NOTIFY_DONE or NOTIFY_STOP.
>
> - The default priority level is zero now.
>
> - Multiple handlers now allowed to be registered at the default
> priority level.
>
> - Power-off call chain is atomic now, like the restart chain.
>
> - kernel/reboot.c changes are split up into several logical patches.
>
> - Added r-b from Michał Mirosław to unmodified patches from v7.
>
> - Added acks that were missing in v7 by accident.
The v8 looks much better than the previous versions to me.
I actually don't really have any comments on it except for the minor
remark regarding patch [1/27] sent separately.
Please just send an update of that one patch and I will queue up the
series for 5.19.
However, I'm going to send a pull request with it in the second half
of the merge window, after the majority of the other changes in the
subsystems touched by it have been integrated.
> v7: - Rebased on a recent linux-next. Dropped the recently removed
> NDS32 architecture. Only SH and x86 arches left un-acked.
>
> - Added acks from Thomas Bogendoerfer and Krzysztof Kozlowski
> to the MIPS and memory/emif patches respectively.
>
> - Made couple minor cosmetic improvements to the new API.
>
> - A month ago I joined Collabora and continuing to work on this series
> on the company's time, so changed my email address to collabora.com
>
> v6: - Rebased on a recent linux-next.
>
> - Made minor couple cosmetic changes.
>
> v5: - Dropped patches which cleaned up notifier/reboot headers, as was
> requested by Rafael Wysocki.
>
> - Dropped WARN_ON() from the code, as was requested by Rafael Wysocki.
> Replaced it with pr_err() appropriately.
>
> - Dropped *_notifier_has_unique_priority() functions and added
> *_notifier_chain_register_unique_prio() instead, as was suggested
> by Michał Mirosław and Rafael Wysocki.
>
> - Dropped export of blocking_notifier_call_chain_is_empty() symbol,
> as was suggested by Rafael Wysocki.
>
> - Michał Mirosław suggested that will be better to split up patch
> that adds the new API to ease reviewing, but Rafael Wysocki asked
> not add more patches, so I kept it as a single patch.
>
> - Added temporary "weak" stub for pm_power_off() which fixes linkage
> failure once symbol is removed from arch/* code. Previously I missed
> this problem because was only compile-testing object files.
>
> v4: - Made a very minor improvement to doc comments, clarifying couple
> default values.
>
> - Corrected list of emails recipient by adding Linus, Sebastian,
> Philipp and more NDS people. Removed bouncing emails.
>
> - Added acks that were given to v3.
>
> v3: - Renamed power_handler to sys_off_handler as was suggested by
>
