linux-kernel - Re: [PATCH 3/3][update] PM / sleep: Introduce command line argument for sleep state enumeration

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Date:	Fri, 01 Aug 2014 15:54:32 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Pavel Machek <pavel@....cz>
Cc:	Linux PM list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3][update] PM / sleep: Introduce command line argument for sleep state enumeration

On Wednesday, July 30, 2014 12:55:29 PM Pavel Machek wrote:
> Hi!
> 
> > For this reason I'm considering changing the defaul behavior going forward (so
> > that "mem" is always present and means "the deepest sleep state available other
> > than hibernation"), but I don't want to do that in one go.
> 
> Actually, I don't think that's good idea, at least on PC.
> 
> The way to wake up from S3 is power button. The way to wake up from
> "echo freeze > state" is going to be different, right?

No, it isn't.  That's the point among other things.

> If I disable S3 in the BIOS and get different result from "echo mem >
> state", that will be confusing.

It may or may not be, depending on how different the handling of the states
is.  It shouldn't be much different.

> Similar (but less severe) problem is there with S1, as it will
> probably power down USB ports, etc.

Hmm.  S1 is implemented very rarely AFAICS and usually it works in analogy
with suspend-to-idle, but in the firmware.

> So for example if I have system with S1, learn to do "echo mem >
> state" and that it still charges my phone, then ACPI updates come and
> "echo mem > state" now puts it in S3 and not charging my phone -- that
> would be confusing.

Yes, it would.

Rafael

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