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Wysocki (Intel) wrote: > External email: Use caution opening links or attachments > > > On Mon, Nov 9, 2026 at 6:01 PM Rafael J. Wysocki (Intel) > wrote: >> >> On Fri, Nov 6, 2026 at 8:35 PM Sumit Gupta wrote: >>> >>> Expose the OSPM Nominal Performance register (ACPI 6.6, Section >>> 8.4.6.1.2.6), which conveys the nominal performance level at which the >>> platform may run. Unlike the read-only Nominal Performance register, it >>> is writable, so OSPM can ask for a nominal level below the >>> platform-reported one, which then becomes the boundary between boosted >>> and throttled operation. >>> >>> Add cppc_set_ospm_nominal_perf() to write the register. Per the spec, >>> the value must lie in [Lowest Performance, Nominal Performance], which >>> the caller is responsible for validating. >>> >>> Add cppc_ospm_nominal_perf_supported() to report whether the platform >>> implements the register as writable, since a write-only register cannot >>> be probed by reading it. It uses the same cpc_is_writable() test as the >>> setter, so support is never reported for a register that a write would >>> reject, and takes cpc_desc_lock while looking the descriptor up. >>> >>> The register also joins the writable set that the SystemMemory overlap >>> validation uses, as the driver now writes it and can compete with >>> another control sharing an access unit. >>> >>> Reviewed-by: Christian Loehle >>> Signed-off-by: Sumit Gupta >>> --- >>> drivers/acpi/cppc_acpi.c | 44 ++++++++++++++++++++++++++++++++++++++++ >>> include/acpi/cppc_acpi.h | 10 +++++++++ >>> 2 files changed, 54 insertions(+) >>> >>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c >>> index 5a1f84fddb7f..3a0ecdd1ab11 100644 >>> --- a/drivers/acpi/cppc_acpi.c >>> +++ b/drivers/acpi/cppc_acpi.c >>> @@ -463,6 +463,7 @@ static bool cpc_reg_is_writable(unsigned int reg_idx) >>> case AUTO_SEL_ENABLE: >>> case AUTO_ACT_WINDOW: >>> case ENERGY_PERF: >>> + case OSPM_NOMINAL_PERF: >> >> Sashiko is unhappy about this change: >> >> https://sashiko.dev/#/patchset/20261106193304.3347374-1-sumitg%40nvidia.com > > So I've queued up patches [1-5/8] for 7.5 and I'll wait for a > clarification here. Hi Rafael, Thanks for queuing 1-5. Sorry, I missed this Sashiko error. In v9, if OSPM_NOMINAL_PERF shares an access unit with Performance Limited, its range is no longer checked for overlaps. It is write-only, so another field's read-modify-write over it would write undefined bits into it. v10 keeps its range reserved, so such a layout is still rejected. Sent v10 of patches 6-8 on top of the queued 1-5 [1]. [1] https://lore.kernel.org/lkml/20261109195400.3600561-1-sumitg@nvidia.com/ Thanks, Sumit