On Mon, Jan 08, 2018 at 12:13:34PM +0100, Koen Vandeputte wrote: > > > On 2018-01-08 12:00, Lorenzo Pieralisi wrote: > >[+cc Joao, Jingoo] > > > >On Mon, Jan 08, 2018 at 09:51:37AM +0100, Koen Vandeputte wrote: > > > >[...] > > > >>[ Node 4 | node-4 ] lspci -v > >>00:00.0 PCI bridge: Synopsys, Inc. Device abcd (rev 01) (prog-if 00 > >>[Normal decode]) > >> Flags: bus master, fast devsel, latency 0, IRQ 298 > >> Memory at 01000000 (32-bit, non-prefetchable) [size=1M] > >> Bus: primary=00, secondary=01, subordinate=01, sec-latency=0 > > ^^^^^^^^^^^^^^ > > > >So basically, the subordinate number in the root port does not > >affect config space forwarding from what I see and it has always > >been like that for dwc. > > > >You are forced to update it to 0xff because otherwise the kernel > >stops enumerating bus numbers > 1 > Indeed, which affects all devices using Designware PCIe init + a > PCIe bridge downstream > >but that's a software issue > >not HW - the subordinate bus number does not seem to affect anything > >here. > > >Sigh. > > > >Another option would consist in forcing the kernel to reassign > >all bus numbers by setting the PCI_REASSIGN_ALL_BUS flag but > >that's not a good idea given how inconsistent that flag usage is. > > > >I think that updating the subordinate bus numbers in the DWC > >config register is the correct solution to make sure the kernel > >won't get confused anymore by what seems to be a fake root port, > >I need input from DWC maintainers to confirm my understanding. > > > >Thanks, > >Lorenzo > > > > The patch I'm currently using internally: > > > --- a/drivers/pci/host/pcie-designware.c > +++ b/drivers/pci/host/pcie-designware.c > @@ -861,7 +861,7 @@ void dw_pcie_setup_rc(struct pcie_port * > /* setup bus numbers */ > val = dw_pcie_readl_rc(pp, PCI_PRIMARY_BUS); > val &= 0xff000000; > - val |= 0x00010100; > + val |= 0x00ff0100; > dw_pcie_writel_rc(pp, PCI_PRIMARY_BUS, val); > > /* setup command register */ > > > Above version logically fixes it for all dwc devices using a bridge > after the RC, not only imx6. > If this is fine, I would submit the patch above and drop the current one. It is fine by me but I won't merge it till I get ACKs and tested-by from the respective maintainers - it can have potential widespread impact. > Backporting this to stable kernels (4.9 .. 4.4 .. etc) will fix all > nasty warnings on these setups during boot without any change in > functionality. > These kernels will require a separate patch as this source file got > moved & renamed. > Thanks for your time and analysis so far, Thank you for reporting it and fixing it. Lorenzo
