On Thursday 27 February 2014 12:36:27 Jason Gunthorpe wrote: > On Thu, Feb 27, 2014 at 07:12:59PM +0000, Liviu Dudau wrote: > > The outstanding issue is how to fix pci_address_to_pio() as it will not > > for for range->cpu_addr > IO_SPACE_LIMIT (16MB in my case). > > The default actually looks fine to me, it is the correct behavior for > systems that actually have a dedicated IO space (like x86) where the > 'CPU' value for IO is the exact value used in the IO accessor > instructions. In this case the IO_SPACE_LIMIT test is appropriate. Right. > It also looks correct for architectures that use the CPU MMIO address > as the IO address directly (where IO_SPACE_LIMIT would be 4G) Are you aware of any that still do? I thought we had stopped doing that. > Architectures that use the virtual IO window technique will always > require a custom pci_address_to_pio implementation. Hmm, at the moment we only call it from of_address_to_resource(), which in turn does not get called on PCI devices, and does not call pci_address_to_pio for 'simple' platform devices. The only case I can think of where it actually matters is when we have ISA devices in DT that use an I/O port address in the reg property, and that case hopefully won't happen on ARM32 or ARM64. > BTW, something that occured to me after reading the patches: > > For ARM64 you might want to think about doing away with the fixed > virtual IO window like we see in ARM32. Just use the CPU MMIO address > directly within the kernel, and implement a ioport_map to setup the MM > on demand. > > I think the legacy reasons for having all those layers of translation > are probably not applicable to ARM64, and it is much simpler without > the extra translation step.... > > Arnd, what do you think? Either I don't like it or I misunderstand you ;-) Most PCI drivers normally don't call ioport_map or pci_iomap, so we can't just do it there. If you are thinking of calling ioport_map for every PCI device that has an I/O BAR and storing the virtual address in the pci_dev resource, I don't see what that gains us in terms of complexity, and it will also break /dev/port. Arnd -- 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
