From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261682AbVGZPt0 (ORCPT ); Tue, 26 Jul 2005 11:49:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261829AbVGZPsK (ORCPT ); Tue, 26 Jul 2005 11:48:10 -0400 Received: from prgy-npn1.prodigy.com ([207.115.54.37]:60166 "EHLO oddball.prodigy.com") by vger.kernel.org with ESMTP id S261682AbVGZPpy (ORCPT ); Tue, 26 Jul 2005 11:45:54 -0400 Message-ID: <42E65BAB.7030806@tmr.com> Date: Tue, 26 Jul 2005 11:50:03 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.8) Gecko/20050511 X-Accept-Language: en-us, en MIME-Version: 1.0 To: "Brown, Len" , Linux Kernel Mailing List Subject: Re: Variable ticks References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Brown, Len wrote: > > >>>>Question one, are there other actions to consider? >>> >>> >>>Yes. >>>Speaking for ACPI C3 state, note that DMA also >>>wakes up the CPU -- even if there was no device interrupt. >>>(aka, "the trouble with USB") >> >>Trouble? Why would USB do DMA unless there was a device activity? > > > look here: > http://www.google.com/search?hl=en&q=usb+selective+suspend > > Linux is working on it too, but it is in development. Somehow I didn't ask that right... The stuff on selective disable is interesting, but my question is why a USB device, call it a keyboard, would do DMA unless I press a key, at which point response will be better if the CPU wakes up out of C3. I understand that specialty attachments may send what amounts to keep alives, or gather data (webcam) you don't want, but the typical mouse and KB would seem to be things which generate DMA at user initiation, and would not be blocked for low power, only for suspend. -- -bill davidsen (davidsen@tmr.com) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me