From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [PATCH] iommu/arm-smmu: request pcie devices to enable ACS Date: Tue, 14 Jun 2016 09:56:27 +0100 Message-ID: <20160614085627.GA19407@arm.com> References: <1465809617-13003-1-git-send-email-Wei.Chen@arm.com> <20160613124531.GE1605@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Wei Chen Cc: Wei Chen , steve.capper-5wv7dgnIgG8@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: iommu@lists.linux-foundation.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