On Tue, Sep 15, 2015 at 07:02:54PM +0100, David Daney wrote: > On 09/15/2015 10:49 AM, Will Deacon wrote: > > On Sat, Sep 12, 2015 at 12:21:57AM +0100, David Daney wrote: > >> /* Limit the bus-range to fit within reg */ > >> - bus_max = pci->cfg.bus_range->start + > >> - (resource_size(&pci->cfg.res) >> pci->cfg.ops.bus_shift) - 1; > >> + bus_max = (resource_size(&pci->cfg.res) >> pci->cfg.ops.bus_shift) - 1; > >> + if (bus_max > 255) > >> + bus_max = 255; > >> pci->cfg.bus_range->end = min_t(resource_size_t, > >> pci->cfg.bus_range->end, bus_max); > > > > Hmm, this is changing the meaning of the bus-range property in the > > device-tree, which really needs to match what IEEE Std 1275-1994 requires. > > I doesn't change the bus-range. Not directly, but pci->cfg.bus_range is a resource populated from the "bus-range" property in the device-tree, so it's changing how the driver uses that property. > > My understanding was that the bus-range could be used to offset the config > > space, which is why it's subtracted from the bus number in > > gen_pci_map_cfg_bus_[e]cam. > > There is an inconsistency in the current code. The calculation of the > cfg.win[?] pointers is done such that the beginning of the config space > specified in the "reg" property corresponds to bus 0. I don't follow you here. The mapping functions explicitly subtract the start of the bus range when calculating the window offset: resource_size_t idx = bus->number - pci->cfg.bus_range->start; so if I have bus-range = <128 255>; then bus 128 lives at the start of the configuration space described by the reg property, not bus 0. Sorry if I'm being thick; I just can't see the inconsistency. > The calculation that I am changing, was done such that the beginning of > the config space specified in the "reg" property corresponds to the > first bus of the "bus-range" > > Which is correct? I assumed that the config space specified in the > "reg" property corresponds to bus 0. Based on this assumption, I made > the bus_max calculation match. > > Due to hardware peculiarities, our bus-range starts at a non-zero bus > number. So, something has to be done to make all the code agree on a > single interpretation of the meaning "reg" property. I think you're the first to exercise this code, so it's definitely worth us fixing whatever's going wrong. > > Also, why is your config space so large that > > we end up overflowing bus_max? > > It isn't. The part of the patch that changes the type from u8 to int > was just to add some sanity. The code was easily susceptible to > overflow failures, it seemed best to change to int. Can we drop this part for now if it's not actually needed? Will -- 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
