[RFC PATCH 0/3] iommu/arm-smmu-v3: Add debug interfaces for SMMUv3

From: Zhou Wang <wangzhou1@hisilicon.com>
To: Will Deacon <will@kernel.org>, Rob Herring <robh@kernel.org>
Cc: iommu@lists.linux-foundation.org,
	Zhou Wang <wangzhou1@hisilicon.com>,
	linux-arm-kernel@lists.infradead.org, chenxiang66@hisilicon.com
Subject: [RFC PATCH 0/3] iommu/arm-smmu-v3: Add debug interfaces for SMMUv3
Date: Fri, 29 Jan 2021 17:06:21 +0800	[thread overview]
Message-ID: <1611911184-116261-1-git-send-email-wangzhou1@hisilicon.com> (raw)

This RFC series is the followed patch of this discussion:
https://www.spinics.net/lists/arm-kernel/msg866187.html. 

Currently there is no debug interface about SMMUv3 driver, which makes it
not convenient when we want to dump some information, like the value of
CD/STE, S1/S2 page table, SMMU registers or cmd/event/pri queues.

This series tries to add support of dumping CD/STE and page table. The
interface design is that user sets device/pasid firstly by sysfs files
and then read related sysfs file to get information:

 (currently only support PCI device)
 echo <domain>:<bus>:<dev>.<fun> > /sys/kernel/debug/iommu/smmuv3/pci_dev
 echo <pasid> > /sys/kernel/debug/iommu/smmuv3/pasid

 Then value in CD and STE can be got by:
 cat /sys/kernel/debug/iommu/smmuv3/ste
 cat /sys/kernel/debug/iommu/smmuv3/cd

 S1 and S2 page tables can be got by:
 cat /sys/kernel/debug/iommu/smmuv3/pt_dump_s1
 cat /sys/kernel/debug/iommu/smmuv3/pt_dump_s2

For STE, CD and page table, related device and pasid are set in pci_dev
and pasid files as above.

First and second patch export some help functions or macros in arm-smmu-v3
and io-pgtable-arm codes, so we can reuse them in debugfs.c. As a RFC, this
series does not go further to dump SMMU registers and cmd/event/pri queues.
I am not sure this series is in the right way, so let's post it out and have a
discussion. Looking forward to any feedback.

Zhou Wang (3):
  iommu/arm-smmu-v3: Export cd/ste get functions
  iommu/io-pgtable: Export page table walk needed functions and macros
  iommu/arm-smmu-v3: Add debug interfaces for SMMUv3

 drivers/iommu/Kconfig                       |  11 +
 drivers/iommu/arm/arm-smmu-v3/Makefile      |   1 +
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c |  10 +-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h |  10 +
 drivers/iommu/arm/arm-smmu-v3/debugfs.c     | 398 ++++++++++++++++++++++++++++
 drivers/iommu/io-pgtable-arm.c              |  47 +---
 drivers/iommu/io-pgtable-arm.h              |  43 +++
 7 files changed, 475 insertions(+), 45 deletions(-)
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/debugfs.c

-- 
2.8.1

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