From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH 2/2] Fix console handling during suspend/resume Date: Thu, 15 Jun 2006 19:51:22 +0200 Message-ID: <20060615175122.GF23859@elf.ucw.cz> References: <1150324014.21941.23.camel@localhost.localdomain> <20060614224436.GF7751@elf.ucw.cz> <20060614235713.GA24859@elf.ucw.cz> <20060615161721.GB23859@elf.ucw.cz> <20060615165909.GE23859@elf.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-pm-bounces@lists.osdl.org Errors-To: linux-pm-bounces@lists.osdl.org To: Linus Torvalds Cc: Power management list List-Id: linux-pm@vger.kernel.org Hi! > > To have DMAs stopped, you need to "freeze" the devices. > = > No you don't. = > = > You need to stop the high-level _queues_, but that's something totally = > different from actually stopping the _devices_. Well, I believe you need the low-level devices, too. Even with high-level queues stopped, drivers may still do some DMA. (USB is the example, as is network receiving packet). > But that's fundamental: and it has absolutely zero to do with device = > suspend (although you do want to tell the device about it - a number of = > devices that do polling even in the absense of user input should probably = > take the hint from "save your state"). Heh, yes, that's what we are doing :-). FREEZE tells devices to stop DMA and save state. It is just... most devices tend to implement FREEZE and SUSPEND with some code; and because SUSPEND implies stopping DMA (plus some powersaving), it is actually okay (but slower than it could be). Pavel -- = (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html