linux-kernel - Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

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Date:	Tue, 1 Jun 2010 00:17:13 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	James Bottomley <James.Bottomley@...e.de>
cc:	Peter Zijlstra <peterz@...radead.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	tytso@....edu, LKML <linux-kernel@...r.kernel.org>,
	Florian Mickler <florian@...kler.org>,
	Linux PM <linux-pm@...ts.linux-foundation.org>,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	felipe.balbi@...ia.com, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [linux-pm] [PATCH 0/8] Suspend block api (version 8)

On Mon, 31 May 2010, James Bottomley wrote:

> On Mon, 2010-05-31 at 22:49 +0200, Thomas Gleixner wrote:
> > On Sat, 29 May 2010, James Bottomley wrote:
> > > The job of the kernel is to accommodate hardware as best it can ...
> > > sometimes it might not be able to, but most of the time it does a pretty
> > > good job.
> > > 
> > > The facts are that C states and S states are different and are entered
> > > differently. 
> > 
> > That's an x86'ism which is going away. And that's really completely
> > irrelevant for the mobile device space. Can we please stop trying to
> > fix todays x86 based laptop problems? They are simply not fixable.
> 
> You're the one mentioning x86, not me.  I already explained that some
> MSM hardware (the G1 for example) has lower power consumption in S3
> (which I'm using as an ACPI shorthand for suspend to ram) than any
> suspend from idle C state.

Those machines can go from idle into S2RAM just fine w/o touching the
/sys/power/state S2RAM mechanism.

It's just a deeper "C" state, really.

The confusion is that S3 is considered to be a complete different
mechanism - which is true for PC style x86 - but not relevant for
hardware which is sane from the PM point of view.

Now some people think, that suspend blockers are a cure for the
existing x86/ACPI/BIOS mess, which cannot go to S3 from idle, but
that's simply not feasible.

Thanks,

	tglx
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