On Thu, Feb 27, 2014 at 08:22:12PM +0000, Arnd Bergmann wrote: > On Thursday 27 February 2014 13:07:29 Jason Gunthorpe wrote: > > On Thu, Feb 27, 2014 at 08:48:08PM +0100, Arnd Bergmann wrote: > > > > 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. > > > > I thought ia64 used to, but it has been a long time since I've touched > > one... > > They have a different way of doing it now, no idea how it looked in > the past: > > #define IO_SPACE_LIMIT 0xffffffffffffffffUL > > #define MAX_IO_SPACES_BITS 8 > #define MAX_IO_SPACES (1UL << MAX_IO_SPACES_BITS) > #define IO_SPACE_BITS 24 > #define IO_SPACE_SIZE (1UL << IO_SPACE_BITS) > > #define IO_SPACE_NR(port) ((port) >> IO_SPACE_BITS) > #define IO_SPACE_BASE(space) ((space) << IO_SPACE_BITS) > #define IO_SPACE_PORT(port) ((port) & (IO_SPACE_SIZE - 1)) > > #define IO_SPACE_SPARSE_ENCODING(p) ((((p) >> 2) << 12) | ((p) & 0xfff)) > > So their port number is a logical token that contains the I/O space number > and a 16MB offset. > > Apparently sparc64 uses physical memory addressing for I/O space, the > same way they do for memory space, and they just set IO_SPACE_LIMIT to > 0xffffffffffffffffUL. > > > > > 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. > > > > Sure, I ment, after Liviu's patch it will become required since he is > > cleverly using it to figure out what the io mapping the bridge driver > > setup before calling the helper. > > Ok. I was arguing more that we should add this dependency. I've thought about this last night and I think I was trying to be too clever for my own good. As Jason points out, arm64 needs its own version of pci_address_to_pio(). I have an idea on how to borrow the powerpc/microblaze one and make it useful without the need for pci_controller *hose. It would be generic enough for other platforms that use virtual I/O windows can use, but I'll start with it being defined for arm64 for discussions in this list. I'll post v3 shortly. Best regards, Liviu > > > > > 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 > > > > Okay, that was one of the 'legacy reasons'. Certainly lots of drivers > > do call pci_iomap, but if you think legacy drivers that don't are > > important to ARM64 then it makes sense to use the virtual IO window. > > I think all uses of I/O space are legacy, but I don't think that > drivers doing inb/outb are more obsolete than those doing pci_iomap. > It's got more to do with the subsystem requirements, e.g. libata > requires the use of pci_iomap. > > > > 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 > > > > Mainly we get to drop the fancy dynamic allocation stuff for the fixed > > virtual window, and it gives the option to have a 1:1 relationship > > between CPU addresses and PCI BARs. > > I don't think the allocation is much of a problem, as long as we > can localize it in one function that is shared by everyone. > The problems I saw were all about explaining to people how it > works, but they really shouldn't have to know. > > > Arnd > > -- ==================== | I would like to | | fix the world, | | but they're not | | giving me the | \ source code! / --------------- ¯\_(ツ)_/¯ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html