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

[zhenglifeng (A)]

It seems that mario has sent a similar patch:

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

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@xxxxxxxxxx>
> ---
>  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,
>  };
>  
>  /*