Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH V1 11/11] arm64, pci, acpi: Support for ACPI based PCI hostbridge init | Date | Tue, 03 Nov 2015 16:59:28 +0100 |
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On Tuesday 03 November 2015 10:10:21 Sinan Kaya wrote: > > I don't see anywhere in the SBSA spec addendum that the PCI > configuration space section that unaligned accesses *MUST* be supported. > > If this is required, please have this info added to the spec. I can work > with the designers for the next chip. > > Unaligned access on the current hardware returns incomplete values or > can cause bus faults. The behavior is undefined.
Unaligned accesses are not allowed, but any PCI compliant device must support aligned 1, 2 or 4 byte accesses on its configuration space, though the byte-enable mechanism. In an ECAM host bridge, those are mapped to load/store accesses from the CPU with the respective width and natural alignment.
Arnd
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