linux-kernel - Re: [PATCH] PM / s2idle: Export s2idle_set

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Date:   Fri, 23 Oct 2020 12:28:20 +0800
From:   claude yen <claude.yen@...iatek.com>
To:     Sudeep Holla <sudeep.holla@....com>
CC:     "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <wsd_upstream@...iatek.com>, <linux-pm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] PM / s2idle: Export s2idle_set_ops

On Thu, 2020-10-22 at 08:02 +0100, Sudeep Holla wrote:
> On Thu, Oct 22, 2020 at 02:17:48PM +0800, Claude Yen wrote:
> > As suspend_set_ops is exported in commit a5e4fd8783a2
> > ("PM / Suspend: Export suspend_set_ops, suspend_valid_only_mem"),
> > exporting s2idle_set_ops to make kernel module setup s2idle ops too.
> > 
> > In this way, kernel module can hook platform suspend
> > functions regardless of Suspend-to-Ram(S2R) or
> > Suspend-to-Idle(S2I)
> >
> 
> If this is for arm64 platform, then NACK. You must use PSCI and it will
> set the ops and it can't be module.
> 

PSCI uses suspend_set_ops instead. And suspend_set_ops has been
exported years ago.

Suspend-to_Idle(S2I) is another suspend method supported by linux
kernel. The corresponding s2idle_ops can be hooked by s2idle_set_ops
by underlying platforms.  For example, S2I is now introduced into
Mediatek SoC platforms. Besides, power management driver is built as
kernel module.

Mobile platforms are now call for kernel drivers to be kernel modules.
This could help drivers easier to migrate to newer linux kernel.
Ref: https://linuxplumbersconf.org/event/7/contributions/790/

Regards,
Claude