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cxl/acpi: Convert QTG _DSM latencies to picoseconds

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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 51293c565c ("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: 51293c565c ("cxl: Fix incorrect region perf data calculation")
Cc: stable@vger.kernel.org
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://patch.msgid.link/20261009045452.1107921-4-den@valinux.co.jp
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
This commit is contained in:
Koichiro Den 2026-10-09 13:54:52 +09:00 committed by Dave Jiang
parent db4503d457
commit 2658c66a5e
1 changed files with 8 additions and 2 deletions
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10
drivers/cxl/acpi.c
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@ -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;