On Fri, Jun 03, 2016 at 07:57:34AM +0200, Stefan Roese wrote: > Hi Thomas, > > On 02.06.2016 15:18, Thomas Petazzoni wrote: > >On Thu, 2 Jun 2016 14:52:47 +0200, Stefan Roese wrote: > >>Add a check to mvebu_pcie_add_windows() to detect, if an MBus window is > >>already configured. If this is the case (base address, size, target and > >>attribute are identical), then this window is not created. This fixes > >>a problem I'm currently seeing on a custom Armada XP based board, which > >>generates this error upon PCI rescanning (in this case via sysfs): > >> > >>$ echo 1 > /sys/bus/pci/rescan > >>mvebu_mbus: cannot add window '4:e8', conflicts with another window > >>mvebu-pcie soc:pcie-controller: Could not create MBus window at [mem 0x9e000000-0x9e0fffff]: -22 > > > >Thanks for the patch. I am not familiar with what happens during a PCI > >rescan, but shouldn't the MBus windows be deleted and then re-added? > > It does not happen in this rescan case. > > >The pci-mvebu driver deletes the MBus windows for a given PCI device > >when invalid memory base/limits are set in the emulated PCI bridge. > >Shouldn't this happen over a rescan? > > I'm not sure what *should* happen upon rescan. But testing shows, that > no MBus window is removed upon rescan. I just tested what happens, > if the PCI devices are "removed" via sysfs. And this also does not > delete any of the MBus windows. > > >If it doesn't, then the other question is whether the check you're > >adding should be done in the PCI driver or in the MBus driver. > > > >In commit b566e782be32145664d96ada3e389f17d32742e5, we already relaxed > >the checks done by the MBus driver, and since this commit we allow > >different windows to have the same target/attribute. > > > >Should the MBus driver also allow re-creating a window that > >already exists, if all its properties are the same? > > This sounds like a good idea to me. To move this detection / decision > one layer up. So that it will work for other drivers using this > MBus interface as well. I don't know how you want to solve it, but it definitely should be safe to write the bridge window registers multiple times, either with the same values, a new invalid base/limit pair, or a new valid base/limit pair. A complete emulation should handle all those, including disposing of an old valid window and replacing it with a new, different, valid window. And of course, it should handle individual 16-bit writes for the base/limit of the 32-bit windows. Bjorn -- 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
