From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alan Stern Subject: Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code) Date: Thu, 11 Jun 2009 11:22:06 -0400 (EDT) Message-ID: References: <200906111706.16848.oliver@neukum.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from iolanthe.rowland.org ([192.131.102.54]:45611 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753547AbZFKPWE (ORCPT ); Thu, 11 Jun 2009 11:22:04 -0400 In-Reply-To: <200906111706.16848.oliver@neukum.org> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: Oliver Neukum Cc: "Rafael J. Wysocki" , Linux-pm mailing list , ACPI Devel Maling List , LKML On Thu, 11 Jun 2009, Oliver Neukum wrote: > Am Donnerstag, 11. Juni 2009 16:52:03 schrieb Alan Stern: > > > Under this definition all devices behind an inactive link are sus= pended, > > > because they can't do any I/O. =A0Which appears to makes sense, b= ecause > > > their drivers have to be notified before the link is suspended an= d the > > > link has to be turned on for the devices to be able to communicat= e with > > > the CPU and RAM. > > > > > > If this definition is adopted, then it's quite clear that the dev= ice can > > > only be suspended if all of its children are suspended and it's a= lways > > > necessary to resume the parent of a device in order to resume the= device > > > itself. > > > > Okay, I'll agree to that. =A0It should be made clear that a device = which > > is "suspended" according to this definition is not necessarily in a > > low-power state. =A0For example, before powering down the link to a= disk > > drive you might want the drive's suspend method to flush the drive'= s > > cache, but it wouldn't have to spin the drive down. >=20 > This precludes handling busses that have low power states that are > left automatically. If such links are stacked the management of accep= table > latencies cannot be left to the busses. > An actual example are the link states of USB 3.0 I don't understand. Can you explain more fully? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757238AbZFKPWU (ORCPT ); Thu, 11 Jun 2009 11:22:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751230AbZFKPWF (ORCPT ); Thu, 11 Jun 2009 11:22:05 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:45612 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753559AbZFKPWE (ORCPT ); Thu, 11 Jun 2009 11:22:04 -0400 Date: Thu, 11 Jun 2009 11:22:06 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Oliver Neukum cc: "Rafael J. Wysocki" , Linux-pm mailing list , ACPI Devel Maling List , LKML Subject: Re: [patch update] Re: [linux-pm] Run-time PM idea (was: Re: [RFC][PATCH 0/2] PM: Rearrange core suspend code) In-Reply-To: <200906111706.16848.oliver@neukum.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 11 Jun 2009, Oliver Neukum wrote: > Am Donnerstag, 11. Juni 2009 16:52:03 schrieb Alan Stern: > > > Under this definition all devices behind an inactive link are suspended, > > > because they can't do any I/O.  Which appears to makes sense, because > > > their drivers have to be notified before the link is suspended and the > > > link has to be turned on for the devices to be able to communicate with > > > the CPU and RAM. > > > > > > If this definition is adopted, then it's quite clear that the device can > > > only be suspended if all of its children are suspended and it's always > > > necessary to resume the parent of a device in order to resume the device > > > itself. > > > > Okay, I'll agree to that.  It should be made clear that a device which > > is "suspended" according to this definition is not necessarily in a > > low-power state.  For example, before powering down the link to a disk > > drive you might want the drive's suspend method to flush the drive's > > cache, but it wouldn't have to spin the drive down. > > This precludes handling busses that have low power states that are > left automatically. If such links are stacked the management of acceptable > latencies cannot be left to the busses. > An actual example are the link states of USB 3.0 I don't understand. Can you explain more fully? Alan Stern