On Tue, 03 Jun 2014 11:21:10 +0200, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tuesday 03 June 2014 09:44:59 Grant Likely wrote: > > > The reason I think allow an ECAM makes sense in ranges is because it allows for a direct IO read/write to CFG space (w/o any mapping) similar to what one would do for MEM space or IO. > > > > I don't think that's right. PCI addresses are defined as follows: > > phys.hi cell: npt000ss bbbbbbbb dddddfff rrrrrrrr > > phys.mid cell: hhhhhhhh hhhhhhhh hhhhhhhh hhhhhhhh > > phys.low cell: llllllll llllllll llllllll llllllll > > > > where 'ddddd' is the device number (0-31) and 'fff' is the function number (0-7) > > > > Going up by one device number or even function number does not result in > > contiguious address values: > > > > device 0: 0x00000000 00000000 00000000 > > device 1: 0x00000800 00000000 00000000 > > device 2: 0x00001000 00000000 00000000 > > device 3: 0x00001800 00000000 00000000 > > ... > > device 30:0x0000f000 00000000 00000000 > > device 31:0x0000f800 00000000 00000000 > > > > a simple ranges doesn't work transparently because each of those config > > ranges needs to be mapped to a 4k block. I think ranges would need to > > look like this: > > > > ranges = <0x00000000 0 0 0x0ff00000 0x1000>, > > <0x00000800 0 0 0x0ff01000 0x1000>, > > <0x00001800 0 0 0x0ff02000 0x1000>, > > ... > > <0x0000f000 0 0 0x0ff1e000 0x1000>, > > <0x0000f800 0 0 0x0ff1f000 0x1000>; > > > > (I just hacked the above up; I make no claims to it's accuracy for > > actual address values) > > > > But I don't even thing the semantics work there because the address is > > encoded in the phys.hi cell, not the phys.low cell. Incrementing by one > > does not behaves as most bus addresses work. To actually work properly > > we would have needed a way to define a stride of 64bits when > > incrementing config space addresses in a ranges mapping. > > Thanks for clearing that up. I always suspected it was roughly this > way, but never managed to think it through completely before getting > distracted by something else. > > I wonder if the OF definition matches CAM though, if not ECAM, as > CAM is also limited to 256 byte config space per function. It's the same problem for 256 byte entries. The address values don't increment nicely and there is a big block of remapping needed. g. -- 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
