Re: [PATCH v7 00/22] Generic DT bindings for PCI IOMMUs and ARM SMMU

On 14/09/16 09:41, Auger Eric wrote:

Hi,

On 12/09/2016 18:13, Robin Murphy wrote:

quoted

Hi all,

To any more confusing fixups and crazily numbered extra patches, here's
a quick v7 with everything rebased into the right order. The significant
change this time is to implement iommu_fwspec properly from the start,
which ends up being far simpler and more robust than faffing about
introducing it somewhere 'less intrusive' to move toward core code later.

New branch in the logical place:

git://linux-arm.org/linux-rm iommu/generic-v7

For information, as discussed privately with Robin I experience some
regressions with the former and now deprecated dt description.

on my AMD Overdrive board and my old dt description I now only see a
single group:

/sys/kernel/iommu_groups/
/sys/kernel/iommu_groups/0
/sys/kernel/iommu_groups/0/devices
/sys/kernel/iommu_groups/0/devices/e0700000.xgmac

whereas I formerly see

/sys/kernel/iommu_groups/
/sys/kernel/iommu_groups/3
/sys/kernel/iommu_groups/3/devices
/sys/kernel/iommu_groups/3/devices/0000:00:00.0
/sys/kernel/iommu_groups/1
/sys/kernel/iommu_groups/1/devices
/sys/kernel/iommu_groups/1/devices/e0700000.xgmac
/sys/kernel/iommu_groups/4
/sys/kernel/iommu_groups/4/devices
/sys/kernel/iommu_groups/4/devices/0000:00:02.2
/sys/kernel/iommu_groups/4/devices/0000:01:00.1
/sys/kernel/iommu_groups/4/devices/0000:00:02.0
/sys/kernel/iommu_groups/4/devices/0000:01:00.0
/sys/kernel/iommu_groups/2
/sys/kernel/iommu_groups/2/devices
/sys/kernel/iommu_groups/2/devices/e0900000.xgmac
/sys/kernel/iommu_groups/0
/sys/kernel/iommu_groups/0/devices
/sys/kernel/iommu_groups/0/devices/f0000000.pcie

This is the group topology without ACS override. Applying the non
upstreamed "pci: Enable overrides for missing ACS capabilities" I used
to see separate groups for each PCIe components. Now I don't see any
difference with and without ACS override.

OK, having reproduced on my Juno, the problem looks to be that
of_for_each_phandle() leaves err set to -ENOENT after successfully
walking a phandle list, which makes __find_legacy_master_phandle()
always bail out after the first SMMU.

Can you confirm that the following diff fixes things for you?

Robin

--->8---

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index fa892d25004d..ac4aab97c93a 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c

@@ -477,7 +477,7 @@ static int __find_legacy_master_phandle(struct

device *dev, void *data)
 			return 1;
 		}
 	it->node = np;
-	return err;
+	return err == -ENOENT ? 0 : err;
 }

 static struct platform_driver arm_smmu_driver;

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