linux-kernel - Re: s2idle breaks on machines without cpuidle support

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Date:   Thu, 9 Feb 2023 00:19:39 +0900
From:   Kazuki <kazukih0205@...il.com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>
Subject: Re: s2idle breaks on machines without cpuidle support

On Wed, Feb 08, 2023 at 03:03:06PM +0000, Sudeep Holla wrote:
> On Wed, Feb 08, 2023 at 11:43:27PM +0900, Kazuki wrote:
> > On Wed, Feb 08, 2023 at 02:16:58PM +0000, Sudeep Holla wrote:
> 
> [...]
> 
> > > I was about ask you earlier as why can't you implement just system
> > > suspend in PSCI where the last cpu just calls WFI if you are interested
> > > in system sleep state. Or you can implement CPU_SUSPEND with an additional
> > > retention state which enters PSCI implementation just to make sure there is
> > > an active cpuidle driver and the s2idle state machinery works as expected.
> >
> > The machine I have (Macbook with Apple M1) doesn't have PSCI.
> 
> Well, if we are allowing to boot on such a system, then we must allow
> adding a platform specific idle driver. It may be useful once we info
> to add deeper than WFI states.
Hmmm, I thought for arm64, non-PSCI idle drivers were prohibited? Or am
I mistaken here?
> 
> > I guess we should ensure that systems without a cpuidle driver
> > will not suspend maybe around here then.
> >
> 
> Are we ? I thought were making changes to enable it. Or are you saying
> we allow to enter into such a state and render the system unusable, if
> so we need to fix it.
Both as I mentioned in my first email. Apologies if it turned out to
be confusing.

Thanks,
Kazuki