Jun, Jun Sun wrote: > > Gleb, > > Sorry to get back to this late. I have been on a trip. > > If I understand you correctly, your major argument is that "we do scan first, > so that we can do resource assignment more easily because we have got all the > dev structures and lists". Yes. Also, "no code duplication". > > This unfortunately may not work, mainly because the PCI bridge may not be > setup properly so the scan results may be incomplete or invalid. You may control pci_scan_bridge by pcibios_assign_all_busses, just return 0 from the latter and the code in pci_scan_bridge assigns all numbers itself. > > However, I do see your point. Actually the most desirable result might be > that we do the resource assignement while we do the scan. > > I think more and more people are realizing that bus number assignment and > fixup must be done separately and done at the beginning. It is a more > complicated problem. For example, in a multi-CPU cPCI system, you don't want > to re-assign bus numbers unless you are the first CPU to boot up. Thus, pcibios_assign_all_busses should just check CPU number. > > pci_auto.c is not the ultimate solution. But the nice thing is that it solves > the broken firmware problem and yet still works with pci_scan_bus() scheme. > > My personal view is that we ultimately should do something like this: > > 1. do one pass scan for PCI bridges and do bus number assigment or fixup. > > 2. based on the above results, we should have a uniformed access to all > devices on all buses (such as read_pci_config(busno, ...)). > > 3. do another pass of pci scan to discover pci devs and assign proper > resources. You definitely can't mix device discovering and assignment of resources in one pass a on a multi-board cPCI system. While you may implement the algorithm above, I think it isn't necessary. Between my previous mail and your reply, I just implemented pcibios_ calls for a mips board that has 2 PCI busses with a PCI bridge between. Yes, BIOS doesn't initialize PCI properly. What I had to do is just call pci_scan_bus, pci_assign_unassigned_resources, and provide callbacks for - pcibios_fixup_bus (sets bus->resource[] to board private resources describing PCI spaces for root bus and to corresponding bridge resources for child bus. For the latter case, I had to inherit values from parent bus also.) - pcibios_update_resource (just write supplied value to the configuration register) - pcibios_fixup_pbus_ranges (convert addresses on the system bus to addresses on PCI bus) I also implemented registration of resources in the global resource tree, but it's not necessary. The only problem I observed is that PCI code treats 0 as invalid address. It's bad but non-fatal. > > BTW, I think your pcibios_assign_resources(bus) function may have already been > implemented in the current pci code. See pbus_assign_resources(). Those > functions are relatively new. I have not got time to fully digest them yet. I had. Basically, pci_assign_unassigned_resources will do the job if pcibios_fixup_bus will provide places for bus->resources. Regards, Gleb.
