From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [linux-pm] Runtime PM discussion notes Date: Fri, 29 Jul 2011 15:41:05 +0200 Message-ID: <20110729134015.GA1561@ucw.cz> References: <20110711112619.GH5092@opensource.wolfsonmicro.com> <201107131104.06995.rjw@sisk.pl> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:53576 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753436Ab1G2NlP (ORCPT ); Fri, 29 Jul 2011 09:41:15 -0400 Content-Disposition: inline In-Reply-To: <201107131104.06995.rjw@sisk.pl> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: "Rafael J. Wysocki" Cc: Paul Walmsley , Mark Brown , linux-pm@lists.linux-foundation.org, linux-omap@vger.kernel.org Hi! > > > Actually, it just occurred to me that if we're waiting for a system > > > timer and can hand that off to a suitable timer in the PMIC then we can > > > do a suspend to RAM for the deep idle state from the hardware point of > > > view. > > > > Yep. At LinuxCon Cambridge two years ago, we had a discussion about > > whether it would be possible to enter ACPI S-states from CPUIdle (or some > > idle governor) on Intel chips. If I remember correctly, the conclusion > > was that ACPI always disables the screen/backlight, so it would only be > > useful for situations where that was acceptable. Well, auto suspending when screensaver is active would still be useful. (And IIRC some machines kept screen on when in S-state unless driver powered it down... but that might be S1. > The reason why you can't enter ACPI S-states from CPUidle is because you > need to go out of the idle loop to execute some ACPI-specific stuff. Which > is not even specific to Intel chips, but to ACPI in general. The code was little tricky/unclean, but it "worked" for me at one point... I called it "sleepy linux". Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html