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 <wei.c...@arm.com> > --- > 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. Will