Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx> writes: > Hello, > > On Thu, 29 Oct 2020 14:30:22 -0500 > Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > >> We could quirk these NICs to avoid the retrain, but since aardvark and >> mvebu have no obvious connection and WLE200/WLE900 and MT76 have no >> obvious connection, I doubt there's a simple hardware defect that >> explains all these. > > aardvark and mvebu have one very strong connection: they are the only > two drivers making use of the PCI Bridge emulation logic in > drivers/pci/pci-bridge-emul.c: > > drivers/pci$ git grep pci-bridge-emul > akefile:obj-$(CONFIG_PCI_BRIDGE_EMUL) += pci-bridge-emul.o > controller/pci-aardvark.c:#include "../pci-bridge-emul.h" > controller/pci-mvebu.c:#include "../pci-bridge-emul.h" > pci-bridge-emul.c:#include "pci-bridge-emul.h" > > I haven't read the whole thread, but it is important to keep in mind > that on those two platforms, the PCI Bridge seen by Linux is *not* a > real HW bridge. It is faked by the the pci-bridge-emul code. So if this > code has defects/bugs in how it emulates a PCI Bridge behavior, you > might see weird things. Ohh, that's interesting. Why does it need to emulate it? And could this cause things weird interactions like what I'm seeing, where a somewhat buggy device in slot 2 affects the ability to retrain the link also in slot 1, but only if there's no device in slot 3? -Toke
