From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754741Ab1J0Oel (ORCPT ); Thu, 27 Oct 2011 10:34:41 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:61403 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750883Ab1J0Oej (ORCPT ); Thu, 27 Oct 2011 10:34:39 -0400 Message-ID: <4EA96BEA.7060004@oracle.com> Date: Thu, 27 Oct 2011 20:04:18 +0530 From: Ajaykumar Hotchandani User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110414 Lightning/1.0b2 Thunderbird/3.1.10 MIME-Version: 1.0 To: Stefano Stabellini CC: Yinghai Lu , Jesse Barnes , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] PCI: Set device power state to PCI_D0 for device without native PM support References: <4E8C40A8.6080205@oracle.com> <4E92DEC1.5050806@oracle.com> <4E9D8495.4010105@oracle.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet22.oracle.com [156.151.31.94] X-CT-RefId: str=0001.0A090206.4EA96BFB.00DD,ss=1,re=0.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/27/2011 06:44 PM, Stefano Stabellini wrote: > On Tue, 18 Oct 2011, Ajaykumar Hotchandani wrote: >> On 10/13/2011 08:00 PM, Stefano Stabellini wrote: >>> On Mon, 10 Oct 2011, Ajaykumar Hotchandani wrote: >>>> On 10/06/2011 09:47 PM, Stefano Stabellini wrote: >>>>> On Thu, 6 Oct 2011, Yinghai Lu wrote: >>>>>> On Thu, Oct 6, 2011 at 3:39 AM, Stefano Stabellini >>>>>> wrote: >>>>>>> I had the same issue and sent a patch a while ago to fix it, adding >>>>>>> >>>>>>> current_state = PCI_D0 in acpiphp_glue.c:register_slot >>>>>>> >>>>>>> it is strange that this does not work for you: >>>>>>> >>>>>>> http://marc.info/?l=linux-kernel&m=129891002722845&w=2 >>>>>> So guest os has to load acpiphp instead of pciehp? >>>>> maybe pciehp needs to make sure that current_state = D0 in >>>>> pciehp_enable_slot, like acpiphp does >>>> Here, acpi hotplugging is involved. >>>> With your change in register_slot(), device will have proper power state when module is being loaded for the first time after booting. >>>> However, while unload of pci module; following is in pci_device_remove(): >>>> if (pci_dev->current_state == PCI_D0) >>>> pci_dev->current_state = PCI_UNKNOWN; >>>> >>>> So, device power state state will remain PCI_UNKNOWN while module is loaded again. Subsequently, MSI write will do nothing. >>> Does this mean that this bug would actually trigger even with devices that >>> do support _EJ0 and power management? >> Nope. I don't have system to verify. But, for the scenario you mentioned >> (device is hot pluggable, acpi bus power manageable and device with >> pm_cap supported; if I understand it correctly), following is what I >> think should happen: >> - Inside pci_platform_power_transition(), >> platform_pci_power_manageable() will be successful. However, >> platform_pci_set_power_state() will fail (as device supports EJ0) and >> subsequently pci_update_current_state() will not get called. >> - So, current power state of device will not be read and power state of >> device will remain PCI_UNKNOWN. >> - Now, pci_raw_set_power_state() will get called. Here, as current power >> state is PCI_UNKNOWN, pci_write_config_word() will be called with pmcsr >> value as 0. As, last two bits of pmcsr is 0, written power state of >> device will be PCI_D0 now. And subsequently, dev->current_state will be >> assigned as PCI_D0 (by using pci_read_config_word() ). > OK, I understand. > > >>> Because acpi_pci_set_power_state won't set current_state to PCI_D0 >>> because the "hotplug driver will take care of _PSx" (see >>> 10b3dcae0f275e2546e55303d64ddbb58cec7599) but the hotplug driver is not >>> actually invoked when loading again a driver module of an existing pci >>> device (the example you mention above)? >> Can you please elaborate more on this? >> acpi_bus_set_power() will update state of acpi_dev (ACPI_STATE_XX) and >> not pci_dev (PCI_XX). >> And here, issue lies with current_state of pci_dev. > I agree, I was merely stating again what the problem is. > > BTW I am OK with your patch. Should we revert 47e9037ac16637cd7f12b8790ea7ce6680e42168 (your changes in register_slot() ) I think, after this change, it's not needed. Or, am I missing some scenario?