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

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 <[email protected]> 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 <[email protected]>
>> Reviewed-by: Mario Limonciello (AMD) <[email protected]>
>> Reviewed-by: Pierre Gondois <[email protected]>
> 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
>>