From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH] SCSI midlayer power management Date: Wed, 11 Aug 2004 22:19:45 +0200 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040811201944.GA1550@openzaurus.ucw.cz> References: <4119611D.60401@optonline.net> <20040811080935.GA26098@elf.ucw.cz> <411A1B72.1010302@optonline.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:57785 "EHLO atrey.karlin.mff.cuni.cz") by vger.kernel.org with ESMTP id S268217AbUHKU3T (ORCPT ); Wed, 11 Aug 2004 16:29:19 -0400 Content-Disposition: inline In-Reply-To: <411A1B72.1010302@optonline.net> List-Id: linux-scsi@vger.kernel.org To: Nathan Bryant Cc: Pavel Machek , 'James Bottomley' , Linux SCSI Reflector , Linux Kernel list , jgarzik@pobox.com Hi! > >swsusp will then resume disk and write the image, that should not be > >a > >problem. Is it guaranteed that after generic_scsi_suspend() no DMA is > >going on? > > > > > No. Remember that DMA works differently under SCSI than it does under > IDE. SCSI DMA is a host controller feature, whereas under IDE it is > enabled/disabled at the drive level and the drives have special > knowledge of DMA. Since generic_scsi_suspend() is the device level > suspend routine, it is called before the host controller's suspend > routine, (due to depth first traversal of device tree), which is > responsible for disabling the PCI slot. Only after the host > controller is suspended will there be no DMA, but if your real > question is "can I generically control a SCSI disk with PIO for > software suspend" then the answer is NO. For purposes of not No, I do not need PIO. I'll probably need host controller support, too, but even w/o it it should work acceptably. Thanks for the answers. -- 64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms