Re: [PATCH v3 1/2] ACPI: CPPC: Add support for CPPC v4

[Rafael J. Wysocki]

On Thu, May 14, 2026 at 9:49 PM Sumit Gupta <sumitg@xxxxxxxxxx> 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@xxxxxxxxxx>
> Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
> Reviewed-by: Pierre Gondois <pierre.gondois@xxxxxxx>

I can apply this one if there are no objections.

The other patch in the series seems to require more work though.

Mario, does your follow-up series depend on both patches in this one?

> ---
>  drivers/acpi/cppc_acpi.c | 23 +++++++++++++++++------
>  include/acpi/cppc_acpi.h |  8 ++++++--
>  2 files changed, 23 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index f370be8715ae..c76cfafa3589 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 +846,16 @@ 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 && (i - 2) == RESOURCE_PRIORITY) {
> +                       /*
> +                        * 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 Resource Priority not supported\n", pr->id);
> +                       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,
>  };
>
>  /*
> --
> 2.34.1
>
>