Subject: [RFC PATCH v2 0/5] Add debugfs support for ARM SMMUv3

From: Qinxin Xia <[email-masked]>
Date: Sat, 28 Mar 2026 18:17:01 +0800

Add a comprehensive debugfs framework to the ARM SMMUv3 driver,                                                                                                                                                                                                                                                       
providing visibility into internal hardware state for debugging
and performance analysis. The debugfs entries are organized under
/sys/kernel/debug/iommu/arm_smmu_v3/, with per-SMMU instance directories
and per-device stream table entries.
                 
Each SMMU instance provides:
- capabilities – static SMMU features and queue sizes.
- registers – SMMU key registers.
- stream_table/ – a directory per device with subdirectories per Stream ID. 
                 
Each Stream ID subdirectory contains:
- ste – the Stream Table Entry in decoded and raw format.
- cd – all valid Context Descriptors (Stage 1 translation tables) associated with the device.
- a symlink named with the device’s BDF/name pointing to its sysfs directory for easy navigation.
                 
/sys/kernel/debug/iommu/arm_smmu_v3/smmu0/stream_table/
└── <sid>/       
    ├─── ste  
    ├─── cd   
    └─── <dev_name>

Changes since V1:
  Address the comments from Nicolin:
  1.Fixed the incorrect comments and replaced 'kzalloc' with 'kzalloc_obj'
  2.'stream_table_create/stream_table_remove' is called in probe_device/release_device
  3.Reused some functions in the driver

  Address the comments from Robin:
  1.Remove unnecessary CR0*EN extra strings
  2.Remove the limit on ssid

  Address the comments from Robin and Nicolin:
  1.The directory structure has been changed
  2.Added lock protection for the ste_show and cd_show

  Others:
  1.'arm_smmu_debugfs_remove' is added to remove the corresponding debugfs when SMMU device is removed
  2.'arm_smmu_debugfs_remove_stream_table' is added to remove the corresponding stream_dir when device is removed
  3.Use scoped_guard for locks that include return
  4.Added 'open' and 'release' operations to prevent the device from being released during dump
  5.Merged 'stream_table_create' and 'ste_show' into one patch
  6.Some other clean code

- Link: https://lore.kernel.org/all/[email-masked]/

Qinxin Xia (5):
  iommu/arm-smmu-v3: Add basic debugfs framework
  iommu/arm-smmu-v3: Add register display to debugfs
  iommu/arm-smmu-v3: Add Stream Table Entry display to debugfs
  iommu/arm-smmu-v3: Add device symlink in stream table debugfs
  iommu/arm-smmu-v3: Add Context Descriptor display to debugfs

 drivers/iommu/Kconfig                         |  11 +
 drivers/iommu/arm/arm-smmu-v3/Makefile        |   1 +
 .../arm/arm-smmu-v3/arm-smmu-v3-debugfs.c     | 571 ++++++++++++++++++
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c   |  33 +-
 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h   |  32 +
 5 files changed, 646 insertions(+), 2 deletions(-)
 create mode 100644 drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-debugfs.c

-- 
2.33.0