From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756250AbYGVNSA (ORCPT ); Tue, 22 Jul 2008 09:18:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753573AbYGVNRv (ORCPT ); Tue, 22 Jul 2008 09:17:51 -0400 Received: from smtp.extricom.com ([192.114.46.18]:53727 "HELO smtp.extricom.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751023AbYGVNRt (ORCPT ); Tue, 22 Jul 2008 09:17:49 -0400 Message-ID: <4885DD41.9010202@extricom.com> Date: Tue, 22 Jul 2008 16:14:41 +0300 From: Eran Liberty User-Agent: Thunderbird 2.0.0.14 (X11/20080502) MIME-Version: 1.0 To: Matthew Wilcox CC: eran liberty , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Jesse Barnes Subject: Re: [PATCH 2.6.26] PCI: refuse to re-add a device to a bus upon pci_scan_child_bus() References: <48591941.4070408@extricom.com> <4884E0FB.9010909@extricom.com> <20080721194957.GH24246@parisc-linux.org> <20080722114929.GA7337@parisc-linux.org> In-Reply-To: <20080722114929.GA7337@parisc-linux.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org WOW, sorry for the html tags (though I had this Thunderbird under control). Here is the same mail without html tags (hopeully) Matthew, You seem to have a finer grasp of the subject then I do, please correct/educate me on any of the points I raise in the following lines. Matthew Wilcox wrote: > On Tue, Jul 22, 2008 at 11:21:06AM +0300, eran liberty wrote: >>> I think this is your real problem, that you're rescanning the entire >>> bus. I don't think that's the route we'd recommend taking. >> My stating point was that I have loaded a new design into a >> programmable device which sits on the pci device. The new design can >> implement numerous pci devices or non at all. I can think of an easy >> way (or clean one) to scan only the programmable device. Scanning the >> whole bus seemed reasonable. > That's what pci_scan_slot() is for. It scans the first function at the > device number, then (if the header indicates it's a multifunction > device) scans the other functions associated with that device. eg you > could call pci_scan_slot(bus, 0x30) and it will create function 06.0 > (and potentially 06.1, 06.2, ...) > You presumably already have the devfn for the existing device since > you're able to call pci_remove_bus_device(). Each slot represent a single device which can have more then one function. pci_scan_slot is aimed for scanning these multiple functions. I, on the other hand, have programmable device on the pci bus which is, for the sake of this discussion, a complete black box. This black box up on loading can implement more then one device, which can have more then one function each. So as far as I see it, now I need to scan all slots on the bus. But to be honest, upon looking a way to make my device work I dismissed the "pci_scan_slot()" option as It did not reach the "fixup_resource ()" part. >>> Why don't you call pci_scan_slot() instead? You won't get the benefit of >>> pcibios_fixup_bus(), but I'm not convinced that's safe to call on a bus >>> that's already been scanned. >>> >> As said its not exactly a slot its more like a regular pci device that >> someone suddenly welded into the pci bus. Its not a hotplug as well, >> and I do not want to give up on the pcibios_fixup_bus() >> > > Why not? What architecture are you using? What does > pcibios_fixup_bus() do for you? > I work with ARCH=powerpc. pcibios_fixup_bus() will deal with all the resource bars allocation. I needed Linux to renegotiate the resources bars on the PCI devices. > (as a side-note, I'd like to reimplement the pcibios_fixup_*() routines; > I think a lot of what they do can be done more generically these days. > It'll take a while and isn't high on my priority list). > If I can lend a hand there, let me know and I will try to squeeze it in somewhere. > >> As it is, with my patch applied i successfully go over the bus and >> remove my own devices before I reprogram the >> programmable device. >> >> while ((dev = pci_get_device(PCI_VENDOR_ID_MYCOMP,PCI_DEVICE_ID_MYDEV,NULL)) >> != NULL) { >> pci_remove_bus_device(dev); >> pci_dev_put(dev); >> } >> >> Load a new design into it. >> >> Then scan the entire bus and add the newly discovered devices. >> >> bus = null; >> while ((bus = pci_find_next_bus(bus)) != NULL) { >> pci_scan_child_bus(bus); >> pci_bus_assign_resources(bus); >> pci_bus_add_devices(bus); >> } >> >> As seen here, this sequence of instructions seems very intuitive. It >> will fail without the patch upon pci_bus_add_devices(). >> > > Seems utterly unintuitive to me. You're doing a lot of unnecessary work > here, and if you have two cards in your machine, you'll take away both > of them when you reload either of them. > Hmmm, I do want to remove all the devices that are implemented by the programmable unit which is reloaded. I have not considered the possibility of having more then one programmable unit. I guess that the removing part can be more fine tuned as the need arises. > What you should do is cache the pci_bus and the devfn at startup: > > static struct pci_bus *my_bus; > static int my_devfn; > > struct pci_dev *dev = pci_get_device(PCI_VENDOR_ID_MYCOMP, > PCI_DEVICE_ID_MYDEV, NULL); > if (!dev) > return -ENODEV; > my_bus = dev->bus; > my_devfn = dev->devfn; > pci_dev_put(dev); > > when you want to remove it: > > for (func = 0; func < 8; func++) > struct pci_dev *dev = pci_get_slot(my_bus, my_devfn + func); > if (!dev) > continue; > pci_remove_bus_device(dev); > pci_dev_put(dev); > } > > when you want to rescan it: > > pci_scan_slot(my_bus, my_devfn); > > (this only handles one programmable card. The basic idea could be > extended to handle multiple cards if you need to do that). > I think there is a hidden assumption in this code, again please correct me if I missed the point. This code assumes that the devices which will re-appear after the programmable unit is loaded has the same devfn and bus as the devices which were present before the reload. This assumption might be wrong. For example, I have a basic programmable image which has no pci devices at all. upon unloading I do not remove any device (as non are present) and up on reloading I suddenly have two. What is their bus? their devfn? Ultimately I would have expected to find a "int pci_scan_bus(struct pci_bus *bus );" the "pci_scan_child_bus ()" was the closest to the mark Liberty