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

Sumit Gupta
2026-04-27T08:04:45Z

On 27/04/26 12:36, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> It seems that mario has sent a similar patch:
>
> https://lore.kernel.org/all/20260427035520.1427080-3-superm1@kernel.org/

Thank you for sharing.
Yes, both look similar with below two change.
1. REG_OPTIONAL needs the 0x1FC7D0 -> 0x7FC7D0 update to mark
the two new registers optional. This is present in my [PATCH 1/2].
2. For Resource Priority, pkg_data added to cpc_entry.
This is present in Mario's [PATCH 2/6].

Hi Mario,
How would you like to proceed? A few options:
(a) Let both CPPCv4 patches from this series go separately.
(b) Fold the REG_OPTIONAL update from my patch 1/2 into your
patch, and pull my patch 2/2 into your series.
(c) Anything else you'd prefer.
Either way works for me.

Thank you,
Sumit Gupta

>
> 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,
>> };
>>
>> /*