Re: [PATCH 3/3] cxl/acpi: Convert QTG _DSM latencies to picoseconds

[Alison Schofield]

On Fri, Oct 09, 2026 at 01:54:52PM +0900, Koichiro Den wrote:
> The QTG _DSM expects read and write latencies in picoseconds, as
> specified in CXL 3.0, Table 9-30.
> 
> The code base originally kept the latencies passed to the QTG _DSM in
> picoseconds in effect. Commit 51293c565cf4 ("cxl: Fix incorrect region
> perf data calculation") normalized CDAT and host bridge latencies to
> nanoseconds, but did not add a conversion back to picoseconds when
> constructing the _DSM input. Firmware can therefore select QTG IDs using
> understated latencies.
> 
> Convert the latencies to picoseconds when constructing the _DSM input
> package. Multiply in 64 bits and reject latencies that cannot fit in the
> DWORD inputs defined by the specification.

Reviewed-by: Alison Schofield <alison.schofield@xxxxxxxxx>