On 09/11/17 07:01, Ruiyu Ni wrote: > Per the UEFI Spec, GetBarAttributes() should return the Host address. > But current implementation returns the address read from the BAR, > which is the Device address. > Per the description of AddressTranslationOffset in ACPI spec: > "For bridges that translate addresses across the bridge, this is the > offset that must be added to the address on the secondary side to > obtain the address on the primary side."
The ACPI spec also says: "Non-bridge devices must list 0 for all Address Translation offset bits." However, the UEFI spec (v2.7) says, under EFI_PCI_IO_PROTOCOL.GetBarAttributes(): "The ACPI Specification does not define how to the use the Address Translation Offset for non-bridge devices. The UEFI Specification is extending the definition of Address Translation Offset to support systems that have different mapping for HostAddress and DeviceAddress. [...] Address Translation Offset. Offset to apply to the Starting address of a BAR to convert it to a PCI address. This value is zero unless the HostAddress and DeviceAddress for the BAR are different." So, I think the patch is correct, but the commit message should not refer to the ACPI spec. It should refer to / quote the UEFI spec only. > HostAddress = DeviceAddress + AddressTranslationOffset. The sentences from the UEFI spec are "Address Translation Offset. Offset to apply to the Starting address of a BAR to convert it to a PCI address", and "Address Range Minimum. Starting address of BAR." To me this seems to imply that AddrRangeMin is already a host address, and DeviceAddress = AddrRangeMin + AddressTranslationOffset > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ruiyu Ni <[email protected]> > Cc: Ard Biesheuvel <[email protected]> > Cc: Benjamin Herrenschmidt <[email protected]> > Cc: Andrew Fish <[email protected]> > Cc: Dong Wei <[email protected]> > Cc: Laszlo Ersek <[email protected]> > Cc: Bartosz Szczepanek <[email protected]> > --- > MdeModulePkg/Bus/Pci/PciBusDxe/PciIo.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/MdeModulePkg/Bus/Pci/PciBusDxe/PciIo.c > b/MdeModulePkg/Bus/Pci/PciBusDxe/PciIo.c > index cc7125e4fc..852d35d710 100644 > --- a/MdeModulePkg/Bus/Pci/PciBusDxe/PciIo.c > +++ b/MdeModulePkg/Bus/Pci/PciBusDxe/PciIo.c > @@ -1955,7 +1955,7 @@ PciIoGetBarAttributes ( > End->Checksum = 0; > > // > - // Get the Address Translation Offset > + // Get the Address Translation Offset and convert the Device address to > Host address. > // > if (Descriptor->ResType == ACPI_ADDRESS_SPACE_TYPE_MEM) { > Descriptor->AddrTranslationOffset = GetMmioAddressTranslationOffset ( > @@ -1967,6 +1967,7 @@ PciIoGetBarAttributes ( > FreePool (Descriptor); > return EFI_UNSUPPORTED; > } > + Descriptor->AddrRangeMin += Descriptor->AddrTranslationOffset; > } > } > > Actually, let me circle back to the initial problem here (apologies if it's too late for that) -- why are we adding the offset inside the GetBarAttributes() function? Isn't it the caller's responsibility to do the addition after GetBarAttributes() returns? I mean if a PCI driver author reads the UEFI 2.7 spec, the spec seems to give that impression. (I'm sorry if I should have raised these questions last week -- I don't wish to block this patch. Please go ahead if I'm wrong.) Thanks Laszlo _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
