From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: MIME-Version: 1.0 In-Reply-To: <201204162330.12178.rjw@sisk.pl> References: <4F8790F6.5080408@intel.com> <201204132141.58063.rjw@sisk.pl> <201204162330.12178.rjw@sisk.pl> Date: Tue, 17 Apr 2012 13:13:39 +0800 Message-ID: Subject: Re: [RFC PATCH] PCIe: Add PCIe runtime D3cold support From: huang ying To: "Rafael J. Wysocki" Cc: "Yan, Zheng" , bhelgaas@google.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Lin Ming , Zhang Rui , ACPI Devel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-acpi-owner@vger.kernel.org List-ID: On Tue, Apr 17, 2012 at 5:30 AM, Rafael J. Wysocki wrote: >> >> +     return 0; >> >> +} >> >> + >> >> +static int pcie_port_runtime_resume(struct device *dev) >> >> +{ >> >> +     struct pci_dev *pdev = to_pci_dev(dev); >> >> + >> >> +     pci_restore_state(pdev); >> >> +     if (pdev->runtime_d3cold) >> >> +             msleep(100); >> > >> > What's _that_ supposed to do? >> >> When resume from d3cold, PCIe main link will be powered on again, it >> will take quite some time before the main link go into L0 state. >> Otherwise, accessing devices under the port may return wrong result. > > OK, but this is generic code and as per the standard the link should have been > reestablished at this point already. > > Please don't put some nonstandard-platform-specific quirks like this into > code that's supposed to handle _every_ PCIe system. After checking PCIe spec, I found that the 100ms here has its standard origin :) In PCI Express Base Specification Revision 2.0: Section 6.6.1 Conventional Reset " To allow components to perform internal initialization, system software must wait for at least 100 ms from the end of a Conventional Reset of one or more devices before it is permitted to issue Configuration Requests to those devices " But I think we should move the 100ms delay here to PCIe bus code or PCIe/ACPI code, because that is needed by all PCIe devices for D3cold support. Best Regards, Huang Ying