On Wed, Jun 16, 2021 at 08:43:12PM +0200, Hans de Goede wrote: > On 6/15/21 10:23 PM, Bjorn Helgaas wrote: > > On Tue, Jun 15, 2021 at 12:25:55PM +0200, Hans de Goede wrote: > I've 2 dmesgs from runs both with and without pci=nocrs, the one > with a clean kernel commandline (no special options) yields: > > [ 0.312333] pci_bus 0000:00: root bus resource [io 0x0000-0x0cf7 window] > [ 0.312335] pci_bus 0000:00: root bus resource [io 0x0d00-0xffff window] > [ 0.312336] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window] > [ 0.312337] pci_bus 0000:00: root bus resource [mem 0x65400000-0xbfffffff window] > [ 0.312338] pci_bus 0000:00: root bus resource [bus 00-fe] > > Where as the one with pci=nocrs on the kernel commandline gives: > > [ 0.271766] pci_bus 0000:00: root bus resource [io 0x0000-0xffff] > [ 0.271767] pci_bus 0000:00: root bus resource [mem 0x00000000-0x7fffffffff] > [ 0.271768] pci_bus 0000:00: root bus resource [bus 00-fe] > > Hmm, so assuming that you are right that pci=nocrs only influences > the root resources (and I believe you are), and given that the problem is > that we are getting these errors: > > [ 0.655335] pci 0000:00:15.0: BAR 0: no space for [mem size 0x00001000 64bit] > [ 0.655337] pci 0000:00:15.0: BAR 0: failed to assign [mem size 0x00001000 64bit] > [ 0.655339] pci 0000:00:15.1: BAR 0: no space for [mem size 0x00001000 64bit] > [ 0.655340] pci 0000:00:15.1: BAR 0: failed to assign [mem size 0x00001000 64bit] > [ 0.655342] pci 0000:00:1f.5: BAR 0: no space for [mem size 0x00001000] > > Instead of getting this: > > [ 0.355716] pci 0000:00:15.0: BAR 0: assigned [mem 0x29c000000-0x29c000fff 64bit] > [ 0.355783] pci 0000:00:15.1: BAR 0: assigned [mem 0x29c001000-0x29c001fff 64bit] > > So now I believe that my initial theory for this is probably completely wrong; and > I wonder if the issue is that the _CRS returned root IOMEM window is big enough > to exactly hold the BIOS assigned mappings, but it does not have any free space > allowing the kernel to assign space for the 0000:00:15.0 and 0000:00:15.1 > devices ? > > Assuming that that theory is right, how could we work around this problem? > Or at least do a quick debug patch to confirm that indeed the window is "full" ? I'd be pretty surprised if the host bridge window actually full -- [mem 0x65400000-0xbfffffff] is a pretty big range and these devices only need 4K each. But maybe we aren't smart enough when trying to allocate space. Places like __pci_bus_size_bridges() and __pci_assign_resource() are full of assumptions about what PCI BARs can go where, depending on 64bit-ness, prefetchability, etc. Maybe instrumenting those allocation paths would give some insight. Possibly we should go ahead and merge some permanent pci_dbg() stuff there too. I do note that the working "pci=nocrs" case puts these devices above 4GB. _CRS only told you about host bridge windows *below* 4GB, and Linux will never assign space that's outside the windows (except in the "pci=nocrs" case, of course). > >> This happens specifically for the designware I2C PCI devices on these > >> laptops, causing I2C-HID attached touchpads/touchscreens to not work. > >> > >> Booting with nocrs on these devices results in the kernel itself > >> assigning memory to these devices, fixing things: > > > > "pci=nocrs" to help people repro this or try the same workaround > > elsewhere. > > Not sure what you are trying to say here. Sorry, I just meant that instead of "Booting with nocrs ...", I'd like the commit log to say "Booting with 'pci=nocrs' ..." so that non-expert users reading it will have a bit of a head start on how to try this themselves. Bjorn
