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Date: Wed, 05 Aug 2015 21:50:38 -0700 From: Guenter Roeck <linux@...ck-us.net> To: Yinghai Lu <yinghai@...nel.org> CC: Bjorn Helgaas <bhelgaas@...gle.com>, "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Lorenzo Pieralisi <lorenzo.pieralisi@....com> Subject: Re: [PATCH v3] PCI: Only enable IO window if supported On 08/05/2015 09:25 PM, Yinghai Lu wrote: > On Wed, Aug 5, 2015 at 7:22 PM, Guenter Roeck <linux@...ck-us.net> wrote: >> On 08/05/2015 06:38 PM, Yinghai Lu wrote: >>> >>> On Wed, Aug 5, 2015 at 6:14 PM, Yinghai Lu <yinghai@...nel.org> wrote: >>>> >>>> >>>> It only can avoid warning with bridge, and still have warning on >>>> devices under the bridge. >>>> >>>> also would have problem on transparent bridges, like >>>> >>>> BRIDGE_A ---- BRIDGE_AA----DEVICE_AA >>>> | >>>> \-- BRIDGE_AB ---DEVICE_AB >>>> >>>> if only BRIDGE_A and BRIDGE_AA are transparent, and BRIDGE_AB is not. >>>> >>>> and if pci_bridge_supports_io() return false for BRIDGE_A. >>>> >>>> We will have all three bridges have PCI_BUS_FLAGS_SUPPORTS_IO cleared. >>>> so all will not been sized and will not get assigned io port resource. >>>> >>>> later DEVICE_AA could root bus io port as parent, and get io resource >>>> assigned. >>>> but DEVICE_AB will not get assigned. >>>> >>>> so we should get rid of pci_bridge_supports_io(), and just check root >>>> resource IO port. >>> >>> >>> I would suggest this version instead: >>> >>> Subject: [PATCH] PCI: Only try to assign io port only if root bus support >>> that >>> >> >> Bjorn had asked me to move the IO support check out of >> pci_bridge_check_ranges(). >> It looks like you want to keep it there. >> >> Can you explain your reasons ? Sorry, I just don't understand. > > in pci_alloc_child_bus(), child bus's bus_flags will be assigned with > parent's bus_flags. > > so if one parent bus has bridge's io bar can not changed, then all > children bus will also > have same bus_flags, and their bridge io bar will not used. > > then if BRIDGE_AB is not transparent, we do need to use it's bridge io bar. > If I understand you correctly, we might need to change the code in pci_read_bridge_io() as follows. From if (!(child->bus_flags & PCI_BUS_FLAGS_SUPPORTS_IO)) return; to something like if (!(child->bus_flags & PCI_BUS_FLAGS_SUPPORTS_IO)) { if (dev->transparent) return; child->bus_flags |= PCI_BUS_FLAGS_SUPPORTS_IO; } Would that solve the problem you are concerned about ? Thanks, Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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