From mboxrd@z Thu Jan 1 00:00:00 1970 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 Message-ID: <5802577.H74A3Lg5B3@wuerfel> References: <1445963922-22711-1-git-send-email-tn@semihalf.com> <5638C728.2020503@semihalf.com> <5638CE5D.4030703@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: In-Reply-To: <5638CE5D.4030703@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org To: Sinan Kaya Cc: Tomasz Nowicki , Lorenzo Pieralisi , bhelgaas@google.com, will.deacon@arm.com, catalin.marinas@arm.com, rjw@rjwysocki.net, hanjun.guo@linaro.org, jiang.liu@linux.intel.com, robert.richter@caviumnetworks.com, Narinder.Dhillon@caviumnetworks.com, ddaney@caviumnetworks.com, Liviu.Dudau@arm.com, tglx@linutronix.de, wangyijing@huawei.com, Suravee.Suthikulpanit@amd.com, msalter@redhat.com, linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linaro-acpi@lists.linaro.org List-Id: linux-acpi@vger.kernel.org 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