[PATCH v3 0/2] cxl: Allow passthrough decoders with >16K granularity

[Alison Schofield <alison.schofield@intel.com>]

Changes in v3:
- Program the real IG encoding for an encodable non-interleaving granularity
  instead of always writing EIG=0 (RichardC, Sashiko)
- Update Patch 1 commit msg text and this cover letter text per above change
Link to v2:
https://lore.kernel.org/linux-cxl/cover.1783795720.git.alison.schofield@intel.com/

Changes in v2:
- Rebased on Linux 7.2-rc1
- Only v1 feedback was from Sashiko and that was not an issue
Link to v1:
https://lore.kernel.org/linux-cxl/cover.1781136281.git.alison.schofield@intel.com/

Sashiko reported [1] that region setup rejects valid topologies
containing a passthrough decoder beneath a wide parent interleave. In
these configurations, a passthrough decoder can compute a granularity
above the 16K maximum encodable in the interleave granularity (IG)
field even though non-interleaving decoders do not consume that field.

The first patch avoids validating the interleave granularity of
non-interleaving decoders, encodes the IG field as a don't-care
only when the computed granularity is not encodable, and updates
the sysfs ABI documentation accordingly.

The second patch extends cxl-test with a topology that allows a CXL
unit test to cover this case.

A unit test update for this case is posted for review [2].

[1] https://lore.kernel.org/all/20260530002613.682E71F00893@smtp.kernel.org/
[2] https://lore.kernel.org/all/cover.1781136221.git.alison.schofield@intel.com/


Alison Schofield (2):
  cxl/region: Allow passthrough decoders with >16K granularity
  cxl/test: Add a 2-way 16K root decoder for passthrough testing

 Documentation/ABI/testing/sysfs-bus-cxl |  5 ++-
 drivers/cxl/core/hdm.c                  |  8 ++++-
 drivers/cxl/core/region.c               | 47 ++++++++++++++----------
 tools/testing/cxl/test/cxl.c            | 48 +++++++++++++++++++++++--
 4 files changed, 85 insertions(+), 23 deletions(-)


base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
-- 
2.37.3