On 2014/11/17 22:13, Arnd Bergmann wrote: > On Monday 17 November 2014 18:21:34 Yijing Wang wrote: >> This series is based Linux 3.18-rc1 and Lorenzo Pieralisi's >> arm PCI domain cleanup patches, link: >> https://patchwork.ozlabs.org/patch/407585/ >> >> Current pci scan interfaces like pci_scan_root_bus() and directly >> call pci_create_root_bus()/pci_scan_child_bus() lack flexiblity. >> Some platform infos like PCI domain and msi_chip have to be >> associated to PCI bus by some arch specific function. >> We want to make a generic pci_host_bridge, and make it hold >> the platform infos or hook. Then we could eliminate the lots >> of arch pci_domain_nr, also we could associate some platform >> ops something like pci_get_msi_chip(struct pci_dev *dev) >> with pci_host_bridge to avoid introduce arch weak functions. >> >> This RFC version not for all platforms, just applied the new >> scan interface in x86/arm/powerpc/ia64, I will refresh other >> platforms after the core pci scan interfaces are ok. > > I think overall this is a good direction to take, in particular > moving more things into struct pci_host_bridge so we can > slim down the architecture specific code. Hi Arnd, thanks very much for your review and comments! > > I don't particularly like the way you use the 'pci_host_info' > to pass callback pointers and some of the generic information. > This duplicates some of the issues we are currently trying > to untangle in the arm32 code to make drivers easier to share > between architectures. What arm32 code you are trying to untangle for example ? Introduce pci_host_info here because I want to make the PCI scan interfaces simple to host drviers, host drivers only need to call one scan interface(pci_scan_host_bridge), but from your comments, The combination pci_create_host_bridge() + pci_scan_xx() seems to be more popular. > > As a general approach, I'd rather see generic helper functions > being exported by the PCI core that a driver may or may not > call. > The way you split the interface between things that happen > before scanning the buses (pci_create_host_bridge) and > the actual scanning (__pci_create_root_bus, pci_scan_child_bus) > seems very helpful and I think we can expand that concept further: > > - The normal pci_create_host_bridge() function can contain > all of the DT scanning functions (finding bus/mem/io resources, > finding the msi-parent), while drivers that don't depend on DT > for this information can call the same function and fill the > same things after they have the pci_host_bridge pointer. > > - If a driver needs to set up mapping windows, it can do that after > calling pci_create_host_bridge(). E.g. all the dw_pcie glue drivers > can call a dw_pcie_setup_windows() function that takes the resources > out of the pci_host_bridge pointer before the bus is scanned. > > - The ACPI code can have a completely different way of creating > a struct pci_host_bridge, which is also passed into the same > bus scanning functions, but doesn't have to come from > pci_create_host_bridge. I hope platforms with ACPI or DT could both use pci_create_host_bridge(). Why we need to use two different ways to process it ? > > - The PowerPC of_scan_bus function can take the same pci_host_bridge > pointer that comes from pci_create_host_bridge(), but we'd call > either pci_create_root_bus or of_scan_bus instead of calling > of_scan_bus through an indirect pointer from pci_create_root_bus. > > Arnd > > . > -- Thanks! Yijing -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
