[v2,0/4] iommu: M1 Pro/Max DART support

Message

Janne Grunau May 3, 2022, 6:22 a.m. UTC

Hej,

I've taken over this series to add support for DART on M1 Pro/Max from
Sven.

Since v1 we have discovered further differences in the PTE format. It
has four differences which makes it incompatible with the one in the
M1:

  - the physical addresses are shifted left by 4 bits and and have 2 more
    bits inside the PTE entries
  - the read/write protection flags are at a different position
  - the subpage protection feature is now mandatory. For Linux we can
    just configure it to always allow access to the entire page.
  - BIT(1) tags "uncached" mappings (used for the display controller)

The last difference is the most troublesome since it makes the PTE format
incomaptible with iopte_type(). Handling this inside io-pgtable-arm.c
seems manageable since DART supports just a single block size. It opens
the question at which point we decide that DART uses its own
io_pgtable_ops.

There is second type of DART (t8110) present on M1 Pro/Max SoCs which
uses the same PTE format as t6000.

Janne

Sven Peter (4):
  dt-bindings: iommu: dart: add t6000 compatible
  iommu/io-pgtable: Add DART subpage protection support
  iommu/io-pgtable: Add DART PTE support for t6000
  iommu: dart: Support t6000 variant

 .../devicetree/bindings/iommu/apple,dart.yaml |  4 +-
 drivers/iommu/apple-dart.c                    | 24 +++++-
 drivers/iommu/io-pgtable-arm.c                | 76 ++++++++++++++++++-
 drivers/iommu/io-pgtable.c                    |  1 +
 include/linux/io-pgtable.h                    |  3 +
 5 files changed, 101 insertions(+), 7 deletions(-)


base-commit: 3123109284176b1532874591f7c81f3837bbdc17