From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yijing Wang Subject: Re: [PATCH v9 08/30] PCI: Update pci_host_bridge bus resource Date: Wed, 8 Apr 2015 17:22:05 +0800 Message-ID: <5524F33D.7090800@huawei.com> References: <1428053164-28277-1-git-send-email-wangyijing@huawei.com> <1428053164-28277-10-git-send-email-wangyijing@huawei.com> <20150407224243.GL10892@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150407224243.GL10892@google.com> Sender: linux-m68k-owner@vger.kernel.org List-Id: linux-m68k@vger.kernel.org To: Bjorn Helgaas Cc: Jiang Liu , linux-pci@vger.kernel.org, Yinghai Lu , linux-kernel@vger.kernel.org, Marc Zyngier , linux-arm-kernel@lists.infradead.org, Russell King , dja@axtens.net, x86@kernel.org, Thomas Gleixner , Benjamin Herrenschmidt , Rusty Russell , Tony Luck , linux-ia64@vger.kernel.org, "David S. Miller" , Guan Xuetao , linux-alpha@vger.kernel.org, linux-m68k@lists.linux-m68k.org, Liviu Dudau , Arnd Bergmann , Geert Uytterhoeven , Yijing Wang On 2015/4/8 6:42, Bjorn Helgaas wrote: > On Fri, Apr 03, 2015 at 05:25:42PM +0800, Yijing Wang wrote: >> From: Yijing Wang >> >> Sometimes, the bus resource start number is not equal to >> root bus number. For example, in pci_scan_bus(), we always >> add the default bus resource which start bus number is 0, >> but the root bus number callers given may != 0, so >> we need to update pci_host_bridge bus resource, because we >> would check whether host bridge bus resoruce is confict >> in later patch. > > It's true that pci_scan_bus() always inserts [bus 00-ff]. But I think > that's completely bogus. The caller of pci_scan_bus() supplies a root bus > number X. Any bus numbers below X are useless as far as this host bridge > is concerned, and it's pointless to include them in the range inserted by > pci_scan_bus(). Agree, I think it's better to use the [bus start - FF] instead of [00-FF]. > > I think we'd be better off if we forced every pci_scan_bus() caller to > supply a real non-overlapping bus number range. We probably can't do that > easily because the arch knows the beginning bus number, but some don't know > how to figure out the ending bus number. It seems to have some problems in pci_scan_bus() if we have more than one pci host bridge in a domain. Because we add the default busn_res[00-FF] to resource list in pci_scan_bus(), and pass the resource list to pci_create_root_bus(). The pci root bus would consume the bus range from the start to the 0xFF, and request it from the per-domain resource[00-FF]. So if we have another pci host bridge in this domain, and pass another start bus number, it would fail when the root bus try to request bus resource from per-domain resource. Now only several archs call pci_scan_bus(), I guess they didn't run the code in above case, so we didn't find the bus report. > > Do we have a per-domain structure that tracks the bus numbers in use in the > domain? It seems like if we had one, we could use that to approximate the > end. For example, if the arch scans three root buses, at bus 00, bus 40, > and bus 80, we could start with the first one at [bus 00-ff], and when we > scan the one at bus 40, we could either report a conflict (if the bus 00 > tree included a bus 40) or reduce the first range to [bus 00-3f]. Per-domain resource pci_domain_busn_res is what we are looking for. For simplicity, we could report a conflict and fail when we find a conflict bus resource in system. >> resource_list_for_each_entry(window, resources) >> - if (window->res->flags & IORESOURCE_BUS) >> + if (window->res->flags & IORESOURCE_BUS) { >> + if (bus > window->res->start) >> + window->res->start = bus; > > I see what you're trying to do here, but I think this is the wrong place to > do it. I'd rather figure out a way to insert something other than > busn_resource in pci_scan_bus(). That probably means we need to > dynamically allocate a new busn_res struct. Allocate a new busn_res maybe unnecessary, the bus resource we added to resource list and passed to pci_create_root_bus() will never be used again after we call pci_bus_insert_busn_res(), we may could consider to use local busn_res in pci_scan_bus(). Thanks! Yijing. > >> return; >> + } >> >> pr_info( >> "No busn resource found for pci%04x:%02x, will use [bus %02x-ff]\n", >> -- >> 1.7.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-pci" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > . > -- Thanks! Yijing