Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759577Ab3DZJmU (ORCPT ); Fri, 26 Apr 2013 05:42:20 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:11524 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757225Ab3DZJmS (ORCPT ); Fri, 26 Apr 2013 05:42:18 -0400 Message-ID: <517A4BB0.30608@huawei.com> Date: Fri, 26 Apr 2013 17:41:04 +0800 From: Yijing Wang User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: Yinghai Lu CC: Bjorn Helgaas , "Rafael J. Wysocki" , Huang Ying , David Bulkow , Kenji Kaneshige , "linux-pci@vger.kernel.org" , Linux Kernel Mailing List , Jiang Liu Subject: Re: [PATCH] PCI: Remove duplicate pci_disable_device for pcie port References: <1366940820-15302-1-git-send-email-yinghai@kernel.org> <5179FC4A.4080000@huawei.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.76.69] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2840 Lines: 81 On 2013/4/26 14:20, Yinghai Lu wrote: > On Thu, Apr 25, 2013 at 9:02 PM, Yijing Wang wrote: >> Hi Yinghai, >> We should not remove this additional pci_disable_device(). >> Because we enable pcie port device twice before. The first is pci_enable_brides(), >> in x86, it was called in pci_assign_unassigned_resources(). The second in pcie_port_device_register(). >> So we should call pci_disable_device() twice for pci_dev->enable_cnt balance. >> >> But there is still a problem here. If we unbind a pcie port device pcie port driver, we can not >> use its child devices again, because this pcie port device was disabled absolutely. >> >> So I think we should move the second pci_disable_device() to remove.c. >> >> I sent this patch to Bjorn and following is Bjorn reply >> "And it's not clear to me whether unbinding the >> pcie port driver should disable the bridge at all. I think one could >> argue that the bridge should remain functional even if the driver is >> unloaded, because the PCI core *enables* the bridge even if the driver >> is never loaded." >> >> Yinghai, how do you think about this issue? > Hi Yinghai, Thanks for your comment! We enable_bridges in PCI core code, so I think we should disable device in remove.c(PCI core level), another reason is call second pci_disable_device() in pci_stop_bus_device() is safe, because all child device has been stopped(unbind driver already). > 1. we always enable bridges after assign unassigned resource for boot path > and hotplug path. > we should never call disable for that. I agree "we should never call second disable" unless we stop this sub pci-tree(). Maybe the attached patch last letter is not safe enough, should wait pci bridge complete to stop itself, then call the second pci_disable_device(). > > 2. driver should be keep enable/disable during probe/remove I agree, use enable/disable balance is better. > > looks like we need to rethink pci enable bridge. > > if we want to enable one pci device, we should go up to enable all bridges till > root. Yes, now we enable pci bridges from root to end. like in pci_assign_unassigned_resources(). > > let if we disable one pci device, we need to go up to disable bridge if its all > pci device children get disabled. Yes, This is what I think too. It seems like we only can do this in remove.c > > if there is pci driver is bound with bridge device, those > disable/enable bridge should be skipped. Hmm, currently system achieve this by checking pci_dev->enable_cnt. > > Thanks > > Yinghai > > . > -- Thanks! Yijing -- 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/