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

[Sumit Gupta]

Hi Rafael,


On 01/06/26 23:05, Rafael J. Wysocki wrote:
> External email: Use caution opening links or attachments
>
>
> On Wed, May 27, 2026 at 9:47 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>
> This patch is good to go AFAICS, while there are still comments on the
> second one in the series.
>
> Do you want me to apply this one separately?

Yes please. Patch 1 is independent of patch 2.
I will send patch 2 separately as a v5 after addressing the
review comments.

Thank you,
Sumit Gupta


> > ---
> >   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 ee8352830c32..9b18fb9aab7c 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
> > @@ -110,6 +112,8 @@ enum cppc_regs {
> >          REFERENCE_PERF,
> >          LOWEST_FREQ,
> >          NOMINAL_FREQ,
> > +       OSPM_NOMINAL_PERF,
> > +       RESOURCE_PRIORITY,
> >   };
> >
> >   /*
> > --
> > 2.34.1