Re: [PATCH v4 5/6] cxl/test: Add a topology to test mixed-granularity regions

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 20 Aug 2026 16:31:23 -0700
Alison Schofield <alison.schofield@intel.com> wrote:

> Add a cxl_test topology for mixed-granularity region testing.
> 
> modprobe cxl_test mixed_gran_regions=1 creates three host bridges,
> each with a passthrough host-bridge port above two switch levels
> and four endpoints, for twelve endpoints total.

Why the pass through HB? 
I queried the 2 levels of switches in the docs patch - maybe
you already answered that (I haven't checked just yet)

The spec examples that do multi level interleave are all cross-HB, HB and
then switch.

> 
> Two CFMWS windows are added:
> 1) A 2-way window at 4K gran over two host bridges, that hosts 8-way
> regions at 1K.
> 2) A 3-way window at 512 gran over three host bridges, that hosts
> 6-way regions at 256.
> 
> Both windows also host the same-granularity regions their ways allow.
> 
> Register every mock device through cxl_mock_platform_device_add() so
> the mock array is populated before platform_device_add(), matching the
> ordering the rest of cxl_test relies on to avoid the endpoint-probe
> race in commit d90f236f8b9e ("cxl/test: Update mock dev array before
> calling platform_device_add()").
> 
> NULL-check the legacy topology arrays, which are left empty when
> mixed_gran_regions=1 selects the new topology.
> 
> The default and existing special module params are unaffected.
> 
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>