Hi Ard, Firstly, this patch was meant for my edk2-staging branch, not mainline edk2 - sorry, forgot to edit the subject line!
The issue is that, without this workaround, PCI(e) bridges and devices will be detected multiple times during bus scanning, e.g. a bridge at bus 1 device 0 will also be seen at bus 1 device 1, bus 1 device 2 etc and hence all the devices on the other side of the bridge will be duplicated too. I copied this workaround from the old Juno PCIe driver as I was seeing the same problem when I was testing the Cadence PCIe host bridge library I have been working on. I agree there should probably be a more elegant solution, but I don't know the generic PCI driver code well enough to suggest one at the moment. Regards, Scott. > -----Original Message----- > From: Ard Biesheuvel [mailto:[email protected]] > Sent: 23 May 2017 17:42 > To: Scott Telford <[email protected]> > Cc: [email protected] <[email protected]>; Tian, Feng > <[email protected]>; Zeng, Star <[email protected]> > Subject: Re: [edk2] [PATCH] Copy bus scanning workaround from ARM Juno > PCIe driver. > > On 23 May 2017 at 09:15, Scott Telford <[email protected]> wrote: > > Copy workaround previously in > > > ArmPlatformPkg/ArmJunoPkg/Drivers/PciHostBridgeDxe/PciRootBridge.c:Pci > RbPciRead() > > to RootBridgeIoPciAccess(), to avoid spurious multiple detections when > > scanning buses. > > > > Contributed-under: TianoCore Contribution Agreement 1.0 > > Signed-off-by: Scott Telford <[email protected]> > > --- > > MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c | 13 > +++++++++++++ > > This does not belong in the generic driver. > > Could you please explain in more detail what the issue is? In any > case, we will need to put this workaround in a Juno specific > implementation of PciExpressLib > > > 1 file changed, 13 insertions(+) > > > > diff --git a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c > b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c > > index a0e7e5b..3cca3c1 100644 > > --- a/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c > > +++ b/MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciRootBridgeIo.c > > @@ -945,6 +945,19 @@ RootBridgeIoPciAccess ( > > PciAddress.ExtendedRegister = PciAddress.Register; > > } > > > > + // The UEFI PCI enumerator scans for devices at all possible addresses, > > + // and ignores some PCI rules - this results in some hardware being > > + // detected multiple times. We work around this by faking absent > > + // devices > > + if ((PciAddress.Bus == 0) && ((PciAddress.Device != 0) || > (PciAddress.Function != 0))) { > > + *((UINT32 *)Buffer) = 0xffffffff; > > + return EFI_SUCCESS; > > + } > > + if ((PciAddress.Bus == 1) && ((PciAddress.Device != 0) || > (PciAddress.Function != 0))) { > > + *((UINT32 *)Buffer) = 0xffffffff; > > + return EFI_SUCCESS; > > + } > > + > > Address = PCI_SEGMENT_LIB_ADDRESS ( > > RootBridge->RootBridgeIo.SegmentNumber, > > PciAddress.Bus, > > -- > > 2.2.2 > > > > _______________________________________________ > > edk2-devel mailing list > > [email protected] > > https://urldefense.proofpoint.com/v2/url?u=https- > 3A__lists.01.org_mailman_listinfo_edk2- > 2Ddevel&d=DwIBaQ&c=aUq983L2pue2FqKFoP6PGHMJQyoJ7kl3s3GZ- > _haXqY&r=0b2qZ7fqn6FWL0d7Bhx7saDL- > B7sx3Cxz3HPARO7ozc&m=7SGL_JTC4ZjVpm7zTv_uO5MHMY48vYsBzhKmKB > q66zw&s=W6S9XFt8B-FdfcvWjCtvHTGo3uddEyMfM6BIEMe8dtY&e= _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
