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

[Robin Murphy]

On 14/09/16 09:41, Auger Eric wrote:
> Hi,
> 
> On 12/09/2016 18:13, Robin Murphy wrote:
>> 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;