From 2658c66a5efb5f30f5ced708a5de831845b43f6d Mon Sep 17 00:00:00 2001 From: Koichiro Den Date: Fri, 9 Oct 2026 13:54:52 +0900 Subject: [PATCH] cxl/acpi: Convert QTG _DSM latencies to picoseconds 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. Fixes: 51293c565cf4 ("cxl: Fix incorrect region perf data calculation") Cc: stable@vger.kernel.org Signed-off-by: Koichiro Den Reviewed-by: Alison Schofield Reviewed-by: Dave Jiang Link: https://patch.msgid.link/20261009045452.1107921-4-den@valinux.co.jp Signed-off-by: Dave Jiang --- drivers/cxl/acpi.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/cxl/acpi.c b/drivers/cxl/acpi.c index fb09a5ff48c1..b7ce6b59c680 100644 --- a/drivers/cxl/acpi.c +++ b/drivers/cxl/acpi.c @@ -231,9 +231,10 @@ cxl_acpi_evaluate_qtg_dsm(acpi_handle handle, struct access_coordinate *coord, int entries, int *qos_class) { union acpi_object *out_obj, *out_buf, *obj; + /* QTG _DSM expects latencies in picoseconds. */ union acpi_object in_array[4] = { - [0].integer = { ACPI_TYPE_INTEGER, coord->read_latency }, - [1].integer = { ACPI_TYPE_INTEGER, coord->write_latency }, + [0].integer = { ACPI_TYPE_INTEGER, coord->read_latency * 1000ULL }, + [1].integer = { ACPI_TYPE_INTEGER, coord->write_latency * 1000ULL }, [2].integer = { ACPI_TYPE_INTEGER, coord->read_bandwidth }, [3].integer = { ACPI_TYPE_INTEGER, coord->write_bandwidth }, }; @@ -251,6 +252,11 @@ cxl_acpi_evaluate_qtg_dsm(acpi_handle handle, struct access_coordinate *coord, if (!entries) return -EINVAL; + /* Latency inputs must fit in the DWORD fields defined by the spec. */ + if (coord->read_latency > U32_MAX / 1000 || + coord->write_latency > U32_MAX / 1000) + return -ERANGE; + out_obj = acpi_evaluate_dsm(handle, &acpi_cxl_qtg_id_guid, 1, 1, &in_obj); if (!out_obj) return -ENXIO;