From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Tue, 14 Jun 2016 09:56:27 +0100 Subject: [PATCH] iommu/arm-smmu: request pcie devices to enable ACS In-Reply-To: References: <1465809617-13003-1-git-send-email-Wei.Chen@arm.com> <20160613124531.GE1605@arm.com> Message-ID: <20160614085627.GA19407@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, Jun 14, 2016 at 11:11:36AM +0800, Wei Chen wrote: > On 13 June 2016 at 20:45, Will Deacon wrote: > > On Mon, Jun 13, 2016 at 05:20:17PM +0800, Wei Chen wrote: > >> The PCIe ACS capability will affect the layout of iommu groups. > >> Generally speaking, if the path from root port to the PCIe device > >> is ACS enabled, the iommu will create a single iommu group for this > >> PCIe device. If all PCIe devices on the path are ACS enabled then > >> Linux can determine this path is ACS enabled. > >> > >> Linux use two PCIe configuration registers to determine the ACS > >> status of PCIe devices: > >> ACS Capability Register and ACS Control Register. > >> > >> The first register is used to check the implementation of ACS function > >> of a PCIe device, the second register is used to check the enable status > >> of ACS function. If one PCIe device has implemented and enabled the ACS > >> function then Linux will determine this PCIe device enabled ACS. > >> > >> From the Chapter:6.12 of PCI Express Base Specification Revision 3.1a, > >> we can find that when a PCIe device implements ACS function, the enable > >> status is set to disabled by default and can be enabled by ACS-aware > >> software. > >> > >> ACS will affect the iommu groups topology, so, the iommu driver is > >> ACS-aware software. This patch adds a call to pci_request_acs() to the > >> arm-smmu driver to enable the ACS function in PCIe devices that support > >> it. > >> > >> Signed-off-by: Wei Chen > >> --- > >> drivers/iommu/arm-smmu-v3.c | 2 ++ > >> drivers/iommu/arm-smmu.c | 4 +++- > >> 2 files changed, 5 insertions(+), 1 deletion(-) > > > > Thanks, queued for 4.8 w/ Robin and Eric's reviewed-by tags and the minor > > commit wording change. > > > > Thanks, I will post a v2 patch to include above changes. :/ As above, I've already queued this. Will