On 08/02/2022 11:21, Yicong Yang wrote:

quoted

This patch should be earlier in the series, before the PTT driver, and the comment on hisi_ptt_check_iommu_mapping() should mention what is going on here.

ok I'll reorder the serives and modify the comments of hisi_ptt_check_iommu_mapping() like:

/*
  * The DMA of PTT trace can only use direct mapping, due to some
  * hardware restriction. Check whether there is an iommu or the
  * policy of the iommu domain is passthrough, otherwise the trace
  * cannot work.

IOMMU, capitalize acronyms

  *
  * The PTT device is supposed to behind the arm smmu v3, which
  * should have passthrough the device by a quirk. Otherwise user
  * should manually set the iommu domain type to identity through
  * sysfs.

Sorry, but I don't really understand your meaning here.

I did not think that if we have a default domain then we can change via 
sysfs to anything else.

  */

quoted

quoted

Signed-off-by: Yicong Yang<yangyicong@hisilicon.com>
---
   drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 16 ++++++++++++++++
   1 file changed, 16 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index 6dc6d8b6b368..6f67a2b1dd27 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -2838,6 +2838,21 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
       }
   }
   +#define IS_HISI_PTT_DEVICE(pdev)    ((pdev)->vendor == PCI_VENDOR_ID_HUAWEI && \
+                     (pdev)->device == 0xa12e)

I assume that not all revisions will require this check, right?

So if you are very confident that the next revision will be fixed then I 
would add a check for this current broken revision.

quoted

For current revisions it's necessary.

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