Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753173Ab2KTQEh (ORCPT ); Tue, 20 Nov 2012 11:04:37 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:41045 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752312Ab2KTQEg (ORCPT ); Tue, 20 Nov 2012 11:04:36 -0500 Date: Tue, 20 Nov 2012 11:04:35 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Huang Ying cc: Bjorn Helgaas , , , , "Rafael J. Wysocki" , "Rafael J. Wysocki" Subject: Re: [PATCH] PCI/PM: Keep runtime PM enabled for unbound PCI devices In-Reply-To: <1353398902-21253-1-git-send-email-ying.huang@intel.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1423 Lines: 31 On Tue, 20 Nov 2012, Huang Ying wrote: > For unbound PCI devices, what we need is: > > - Always in D0 state, because some devices does not work again after > being put into D3 by the PCI bus. > > - In SUSPENDED state if allowed, so that the parent devices can still > be put into low power state. > > To satisfy these requirement, the runtime PM for the unbound PCI > devices are disabled and set to SUSPENDED state. One issue of this > solution is that the PCI devices will be put into SUSPENDED state even > if the SUSPENDED state is forbidden via the sysfs interface > (.../power/control) of the device. This is not an issue for most > devices, because most PCI devices are not used at all if unbounded. > But there are exceptions. For example, unbound VGA card can be used > for display, but suspend its parents make it stop working. > > To fix the issue, we keep the runtime PM enabled when the PCI devices > are unbound. But the runtime PM callbacks will do nothing if the PCI > devices are unbound. This way, we can put the PCI devices into > SUSPENDED state without put the PCI devices into D3 state. Acked-by: Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/