From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757951Ab1JRNwx (ORCPT ); Tue, 18 Oct 2011 09:52:53 -0400 Received: from rcsinet15.oracle.com ([148.87.113.117]:23801 "EHLO rcsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757783Ab1JRNww (ORCPT ); Tue, 18 Oct 2011 09:52:52 -0400 Message-ID: <4E9D8495.4010105@oracle.com> Date: Tue, 18 Oct 2011 19:22:21 +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> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: acsinet21.oracle.com [141.146.126.237] X-Auth-Type: Internal IP X-CT-RefId: str=0001.0A090202.4E9D84B0.0019:SCFMA922111,ss=1,re=-4.000,fgs=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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() ). > 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. Thanks, Ajay