Re: [PATCH v5 1/7] Documentation/cxl: Describe mixed-granularity regions

[Jonathan Cameron <jic23@kernel.org>]

On Thu,  3 Sep 2026 16:23:43 -0700
Alison Schofield <alison.schofield@intel.com> wrote:

> Linux has required that a region's interleave granularity equal the
> interleave granularity of its interleaving root decoder. A mixed-
> granularity region lifts that restriction: the region granularity may be
> finer than the root's, so the interleave refines from the root toward the
> endpoints.
> 
> Mixed-granularity region support introduces interleave relationships that
> are not obvious from the existing CXL documentation. This is particularly
> true for the 3-, 6-, and 12-way configurations and for understanding which
> configurations permitted by the CXL Specification are supported by Linux.
> 
> Document the mixed-granularity model and Linux's coarse-to-fine
> restriction. Include the relevant configurations from CXL 4.0 Section
> 9.13.1.1 and annotate their Linux support status.
> 
> This intentionally repeats information from the CXL Specification. The
> specification remains authoritative, but showing the Linux support policy
> alongside the legal configurations ensures readers do not mistake an
> unsupported Linux setup for a configuration unsupported by the CXL
> Specification.
> 
> Assisted-by: Claude:Opus-5
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>