Re: [PATCH 1/2] ACPI: CPPC: Add support for CPPC v4

zhenglifeng (A)
2026-04-27T07:06:57Z

It seems that mario has sent a similar patch:

https://lore.kernel.org/all/20260427035520.1427080-3-superm1@kernel.org/

On 4/27/2026 1:18 PM, Sumit Gupta wrote:
> CPPC v4 (ACPI 6.6, Section 8.4.6) adds two optional entries to the
> _CPC package:
>
> 1. OSPM Nominal Performance (8.4.6.1.2.6): A write-only register that
> lets OSPM inform the platform what it considers nominal performance.
> The platform classifies performance above this level as boost and
> below as throttle for its power/thermal decisions.
>
> 2. Resource Priority (8.4.6.1.2.7): A Package of Resource Priority
> Register Descriptor sub-packages that allow OSPM to set relative
> priority among processors for shared resources (boost, throttle,
> L2/L3 cache, memory bandwidth). Parsing the full structure is not
> yet supported; such entries are marked as unsupported.
>
> Add v4 _CPC table parsing (25 entries) and update REG_OPTIONAL to
> mark the two new registers as optional.
>
> Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
> ---
> drivers/acpi/cppc_acpi.c | 24 ++++++++++++++++++------
> include/acpi/cppc_acpi.h | 8 ++++++--
> 2 files changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index 2e91c5a97761..a1c91ce20cc8 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -134,7 +134,7 @@ static DEFINE_PER_CPU(struct cpc_desc *, cpc_desc_ptr);
> * cpc_regs[] with the corresponding index. 0 means mandatory and 1
> * means optional.
> */
> -#define REG_OPTIONAL (0x1FC7D0)
> +#define REG_OPTIONAL (0x7FC7D0)
>
> /*
> * Use the index of the register in per-cpu cpc_regs[] to check if
> @@ -751,18 +751,19 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
> /*
> * Disregard _CPC if the number of entries in the return package is not
> * as expected, but support future revisions being proper supersets of
> - * the v3 and only causing more entries to be returned by _CPC.
> + * the v4 and only causing more entries to be returned by _CPC.
> */
> if ((cpc_rev == CPPC_V2_REV && num_ent != CPPC_V2_NUM_ENT) ||
> (cpc_rev == CPPC_V3_REV && num_ent != CPPC_V3_NUM_ENT) ||
> - (cpc_rev > CPPC_V3_REV && num_ent <= CPPC_V3_NUM_ENT)) {
> + (cpc_rev == CPPC_V4_REV && num_ent != CPPC_V4_NUM_ENT) ||
> + (cpc_rev > CPPC_V4_REV && num_ent <= CPPC_V4_NUM_ENT)) {
> pr_debug("Unexpected number of _CPC return package entries (%d) for CPU:%d\n",
> num_ent, pr->id);
> goto out_free;
> }
> - if (cpc_rev > CPPC_V3_REV) {
> - num_ent = CPPC_V3_NUM_ENT;
> - cpc_rev = CPPC_V3_REV;
> + if (cpc_rev > CPPC_V4_REV) {
> + num_ent = CPPC_V4_NUM_ENT;
> + cpc_rev = CPPC_V4_REV;
> }
>
> cpc_ptr->num_entries = num_ent;
> @@ -845,6 +846,17 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)
>
> cpc_ptr->cpc_regs[i-2].type = ACPI_TYPE_BUFFER;
> memcpy(&cpc_ptr->cpc_regs[i-2].cpc_entry.reg, gas_t, sizeof(*gas_t));
> + } else if (cpc_obj->type == ACPI_TYPE_PACKAGE) {
> + /*
> + * ACPI 6.6, s8.4.6.1.2.7 defines Resource Priority
> + * as a Package of Resource Priority Register Descriptor
> + * sub-packages. Parsing the full structure is not yet
> + * supported; mark the register as unsupported for now.
> + */
> + pr_debug("CPU:%d entry %d: package type not supported\n",
> + pr->id, i);
> + cpc_ptr->cpc_regs[i-2].type = ACPI_TYPE_INTEGER;
> + cpc_ptr->cpc_regs[i-2].cpc_entry.int_value = 0;
> } else {
> pr_debug("Invalid entry type (%d) in _CPC for CPU:%d\n",
> i, pr->id);
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index d1f02ceec4f9..8693890a7275 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -17,16 +17,18 @@
> #include <acpi/pcc.h>
> #include <acpi/processor.h>
>
> -/* CPPCv2 and CPPCv3 support */
> +/* CPPCv2, CPPCv3 and CPPCv4 support */
> #define CPPC_V2_REV 2
> #define CPPC_V3_REV 3
> +#define CPPC_V4_REV 4
> #define CPPC_V2_NUM_ENT 21
> #define CPPC_V3_NUM_ENT 23
> +#define CPPC_V4_NUM_ENT 25
>
> #define PCC_CMD_COMPLETE_MASK (1 << 0)
> #define PCC_ERROR_MASK (1 << 2)
>
> -#define MAX_CPC_REG_ENT 21
> +#define MAX_CPC_REG_ENT 23
>
> /* CPPC specific PCC commands. */
> #define CMD_READ 0
> @@ -109,6 +111,8 @@ enum cppc_regs {
> REFERENCE_PERF,
> LOWEST_FREQ,
> NOMINAL_FREQ,
> + OSPM_NOMINAL_PERF,
> + RESOURCE_PRIORITY,
> };
>
> /*