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Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , Wei Liu , Dexuan Cui , Lorenzo Pieralisi , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-pci@vger.kernel.org, Sunil Muthuswamy , Mike Rapoport Subject: Re: [RFC v4 1/7] PCI: Introduce domain_nr in pci_host_bridge Message-ID: <20210714193319.GA1867593@bjorn-Precision-5520> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210714102737.198432-2-boqun.feng@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210714_123321_896839_934D2E73 X-CRM114-Status: GOOD ( 34.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Jul 14, 2021 at 06:27:31PM +0800, Boqun Feng wrote: > Currently we retrieve the PCI domain number of the host bridge from the > bus sysdata (or pci_config_window if PCI_DOMAINS_GENERIC=y). Actually > we have the information at PCI host bridge probing time, and it makes > sense that we store it into pci_host_bridge. One benefit of doing so is > the requirement for supporting PCI on Hyper-V for ARM64, because the > host bridge of Hyper-V doesn't have pci_config_window, whereas ARM64 is > a PCI_DOMAINS_GENERIC=y arch, so we cannot retrieve the PCI domain > number from pci_config_window on ARM64 Hyper-V guest. > > As the preparation for ARM64 Hyper-V PCI support, we introduce the > domain_nr in pci_host_bridge and a sentinel value to allow drivers to > set domain numbers properly at probing time. Currently > CONFIG_PCI_DOMAINS_GENERIC=y archs are only users of this > newly-introduced field. Thanks for pushing on this. PCI_DOMAINS_GENERIC is really not very generic today and it will be good to make it more so. > Signed-off-by: Boqun Feng > --- > drivers/pci/probe.c | 6 +++++- > include/linux/pci.h | 10 ++++++++++ > 2 files changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 79177ac37880..60c50d4f156f 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -594,6 +594,7 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge) > bridge->native_pme = 1; > bridge->native_ltr = 1; > bridge->native_dpc = 1; > + bridge->domain_nr = PCI_DOMAIN_NR_NOT_SET; > > device_initialize(&bridge->dev); > } > @@ -898,7 +899,10 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > bus->ops = bridge->ops; > bus->number = bus->busn_res.start = bridge->busnr; > #ifdef CONFIG_PCI_DOMAINS_GENERIC > - bus->domain_nr = pci_bus_find_domain_nr(bus, parent); > + if (bridge->domain_nr == PCI_DOMAIN_NR_NOT_SET) > + bus->domain_nr = pci_bus_find_domain_nr(bus, parent); > + else > + bus->domain_nr = bridge->domain_nr; The domain_nr in struct pci_bus is really only used by pci_domain_nr(). It seems like it really belongs in the struct pci_host_bridge and probably doesn't need to be duplicated in the struct pci_bus. But that's probably a project for the future. > #endif > > b = pci_find_bus(pci_domain_nr(bus), bridge->busnr); > diff --git a/include/linux/pci.h b/include/linux/pci.h > index 540b377ca8f6..952bb7d46576 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -526,6 +526,15 @@ static inline int pci_channel_offline(struct pci_dev *pdev) > return (pdev->error_state != pci_channel_io_normal); > } > > +/* > + * PCI Conventional has at most 256 PCI bus segments and PCI Express has at > + * most 65536 "PCI Segments Groups", therefore -1 is not a valid PCI domain s/Segments/Segment/ Do you have a reference for these limits? I don't think either Conventional PCI or PCIe actually specifies a hardware limit on the number of domains (I think PCI uses "segment group" to mean the same thing). "Segment" in the Conventional PCI spec, r3.0, means a bus segment, which connects all the devices on a single bus. Obviously there's a limit of 256 buses under a single host bridge, but that's different concept than a domain/segment group. The PCI Firmware spec, r3.3, defines "Segment Group Number" as being in the range 0..65535, but as far as I know, that's just a firmware issue, and it applies equally to Conventional PCI and PCIe. I think you're right that -1 is a reasonable sentinel; I just don't want to claim a difference here unless there really is one. > + * number, and can be used as a sentinel value indicating ->domain_nr is not > + * set by the driver (and CONFIG_PCI_DOMAINS_GENERIC=y can set it in generic > + * code). > + */ > +#define PCI_DOMAIN_NR_NOT_SET (-1) > + > struct pci_host_bridge { > struct device dev; > struct pci_bus *bus; /* Root bus */ > @@ -533,6 +542,7 @@ struct pci_host_bridge { > struct pci_ops *child_ops; > void *sysdata; > int busnr; > + int domain_nr; > struct list_head windows; /* resource_entry */ > struct list_head dma_ranges; /* dma ranges resource list */ > u8 (*swizzle_irq)(struct pci_dev *, u8 *); /* Platform IRQ swizzler */ > -- > 2.30.2 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel