[PATCH v3 0/5] Add support for Broadcom BCM2712 IOMMU driver (Raspberry Pi 5)

[Daniel Drake]

Hi,

This series adds a driver for the Broadcom BCM2712 IOMMU found on
Raspberry Pi 5, and hooks up the display controller IOMMU for efficient
management of graphics memory. This is adapted from the downstream driver
from Raspberry Pi (original author Nick Hollinghurst), with main changes:
 - In page mapping mode, operate the translation aperture from address 0,
   with no bypass window. More like a IOMMU and less like a GART.
 - Implement the page table management using generic_pt
 - Support 4MB hugepage mapping in top level page table
 - Implement brcm,iommu-cache as standards-compliant DT property
 - Drop the dma-iova-offset hack, used to work around some issue seen with
   dma-ranges. This will need to be investigated separately and solved
   properly. (It's not needed for display controller iommu support included
   here.)
 - Misc simplifications/standardisations/cleanups
 
The IOMMU works strictly with 4KB pages. This means that unfortunately
when the kernel is compiled with PAGE_SIZE=16KB (the Raspberry Pi 5
kernel default), 12KB is wasted in each page that is allocated for page
tables. I plan to address this in followup work.

It has been tested on Raspberry Pi 5 using a 3D-accelerated graphical
environment which causes plenty of IOMMU maps & unmaps.

Thanks for the review comments and discussion. Further feedback and
testing welcome!

Changes in v3:
- Switch from a aperture and bypass window GART-like approach
  to IOMMU-like 0-based translation
- Add 3 SW bits which seem unused (per the chipset docs); drop patch
  for NO_SW_BIT handling. This reduces the claimed address space, so I had
  to tweak a iommu_pt test accordingly.
- Disallow domain sharing across multiple hardware IOMMU instances
- Clear and flush local MMU TLB during domain attach
- Handle unattached domains safely during TLB sync
- Set cache platform driver data late during probe to prevent race condition
- Improved handling of cache flush timeouts
- Use format string for device name in iommu_device_sysfs_add()
- Use cleanup.h helpers for scope management
- Expand DT binding descriptions for IOMMU and IOMMUC
- Add iommus property to HVS display node in DT
- Drop iommuc back-compat with current RPi DT
- Link to v2: https://lore.kernel.org/r/20260727-bcm2712-iommu-submit-v2-0-0247b5c03de8@xxxxxxxxxxxxxxx

Changes in v2:
- Use iommu_fwspec in xlate & probe_device
- Add blocked_domain support
- Simplify page size configuration between iommu driver and format
- Introduce PT_FEAT_NO_SW_BIT flag to allow formats to explicitly opt-in to
  a defensive flushing algorithm when no sw bit is available
- Implement 4MB pages at Level 1; this is more efficient and means the
  "allow full-table contiguous leaves in unit tests" commit has been
  dropped because it is no longer needed.
- Hardcode the aperture in an unused part of the address space, removing
  it from DT (it's a software-specific decision, not an attribute of the
  hardware), adding more explanatory comments
- Use pt_full_va_prefix to have the PT format operate within the aperture
  space, enabling use of IOMMU_PT_DOMAIN_OPS
- Add more dt-bindings explanation to brcm,iommu-cache and drop docs
  around the cache property used in RPi firmware (the driver still supports
  this however, for fw compat reasons)
- Correct iommu device address in bcm2712.dtsi
- Link to v1: https://lore.kernel.org/r/20260712-bcm2712-iommu-submit-v1-0-80e10cdde2ea@xxxxxxxxxxxxxxx

---
Daniel Drake (5):
      iommu_pt: Fix test_pgsize_boundary() failure on narrow-OA formats
      dt-bindings: iommu: Add Broadcom BCM2712 IOMMU
      iommu/generic_pt: Add Broadcom BCM2712 page table format
      iommu: Add Broadcom BCM2712 IOMMU driver
      arm64: dts: broadcom: bcm2712: Add GPU IOMMU and IOMMU cache nodes

 .../bindings/iommu/brcm,bcm2712-iommu.yaml         |  52 ++
 .../bindings/iommu/brcm,bcm2712-iommuc.yaml        |  38 ++
 arch/arm64/boot/dts/broadcom/bcm2712.dtsi          |  15 +
 drivers/iommu/Kconfig                              |  15 +
 drivers/iommu/Makefile                             |   1 +
 drivers/iommu/bcm2712-iommu-cache.c                |  83 +++
 drivers/iommu/bcm2712-iommu-cache.h                |   9 +
 drivers/iommu/bcm2712-iommu.c                      | 556 +++++++++++++++++++++
 drivers/iommu/generic_pt/.kunitconfig              |   1 +
 drivers/iommu/generic_pt/Kconfig                   |  10 +
 drivers/iommu/generic_pt/fmt/Makefile              |   2 +
 drivers/iommu/generic_pt/fmt/bcm2712.h             | 288 +++++++++++
 drivers/iommu/generic_pt/fmt/defs_bcm2712.h        |  18 +
 drivers/iommu/generic_pt/fmt/iommu_bcm2712.c       |   6 +
 drivers/iommu/generic_pt/kunit_iommu_pt.h          |   2 +-
 include/linux/generic_pt/common.h                  |   6 +
 include/linux/generic_pt/iommu.h                   |  12 +
 17 files changed, 1113 insertions(+), 1 deletion(-)
---
base-commit: 47096fc3d064a07c0842f748b99ebf01be120f2b
change-id: 20260712-bcm2712-iommu-submit-2e09899e65c4

Best regards,
-- 
Daniel Drake <dan@xxxxxxxxxxxxxxx>