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

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Date:   Wed, 8 Feb 2023 15:34:07 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Kazuki <kazukih0205@...il.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>,
        "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 Thu, Feb 09, 2023 at 12:19:39AM +0900, Kazuki wrote:
> On Wed, Feb 08, 2023 at 03:03:06PM +0000, Sudeep Holla wrote:

[...]

> > 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 don't know. I am not against it especially now that we have allowed a
non-PSCI based production system to boot the kernel.

> > 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.

Sorry still confusing. Are you saying you can enter s2idle and crash or
hang the system without changes(especially around this s2idle code) ?

If yes, then it is a bug. If the hang/crash is only after your changes,
we need to check.

-- 
Regards,
Sudeep