linux-kernel - Re: [PATCH v5 04/11] ACPI: CPPC: Extend cppc_set_epp_perf() to support auto

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Message-ID: <d5471fcc-ac74-495f-ab65-18aa870bd5ba@arm.com>
Date: Fri, 16 Jan 2026 16:59:29 +0100
From: Pierre Gondois <pierre.gondois@....com>
To: Sumit Gupta <sumitg@...dia.com>, rafael@...nel.org,
 viresh.kumar@...aro.org, lenb@...nel.org, robert.moore@...el.com,
 corbet@....net, zhenglifeng1@...wei.com, rdunlap@...radead.org,
 ray.huang@....com, gautham.shenoy@....com, mario.limonciello@....com,
 perry.yuan@....com, ionela.voinescu@....com, zhanjie9@...ilicon.com,
 linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
 linux-doc@...r.kernel.org, acpica-devel@...ts.linux.dev,
 linux-kernel@...r.kernel.org
Cc: linux-tegra@...r.kernel.org, treding@...dia.com, jonathanh@...dia.com,
 vsethi@...dia.com, ksitaraman@...dia.com, sanjayc@...dia.com,
 nhartman@...dia.com, bbasu@...dia.com
Subject: Re: [PATCH v5 04/11] ACPI: CPPC: Extend cppc_set_epp_perf() to
 support auto_sel and epp


On 12/23/25 13:13, Sumit Gupta wrote:
> Extend cppc_set_epp_perf() to write both auto_sel and energy_perf
> registers when they are in FFH or SystemMemory address space.
>
> This keeps the behavior consistent with PCC case where both registers
> are already updated together, but was missing for FFH/SystemMemory.
>
> Also update EPP constants for better clarity:
> - Add CPPC_EPP_PERFORMANCE_PREF (0x00) for performance preference
> - Add CPPC_EPP_ENERGY_EFFICIENCY_PREF (0xFF) for energy efficiency
>
> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> ---
>   drivers/acpi/cppc_acpi.c | 35 +++++++++++++++++++++++++++++------
>   include/acpi/cppc_acpi.h |  3 ++-
>   2 files changed, 31 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
> index a4e89fe6aab5..403ee988a8c6 100644
> --- a/drivers/acpi/cppc_acpi.c
> +++ b/drivers/acpi/cppc_acpi.c
> @@ -1556,6 +1556,8 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>   	struct cpc_register_resource *auto_sel_reg;
>   	struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu);
>   	struct cppc_pcc_data *pcc_ss_data = NULL;
> +	bool autosel_ffh_sysmem;
> +	bool epp_ffh_sysmem;
>   	int ret;
>   
>   	if (!cpc_desc) {
> @@ -1566,6 +1568,11 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>   	auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE];
>   	epp_set_reg = &cpc_desc->cpc_regs[ENERGY_PERF];
>   
> +	epp_ffh_sysmem = CPC_SUPPORTED(epp_set_reg) &&
> +		(CPC_IN_FFH(epp_set_reg) || CPC_IN_SYSTEM_MEMORY(epp_set_reg));
> +	autosel_ffh_sysmem = CPC_SUPPORTED(auto_sel_reg) &&
> +		(CPC_IN_FFH(auto_sel_reg) || CPC_IN_SYSTEM_MEMORY(auto_sel_reg));
> +
>   	if (CPC_IN_PCC(epp_set_reg) || CPC_IN_PCC(auto_sel_reg)) {
>   		if (pcc_ss_id < 0) {
>   			pr_debug("Invalid pcc_ss_id for CPU:%d\n", cpu);
> @@ -1590,14 +1597,30 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>   		/* after writing CPC, transfer the ownership of PCC to platform */
>   		ret = send_pcc_cmd(pcc_ss_id, CMD_WRITE);
>   		up_write(&pcc_ss_data->pcc_lock);
> -	} else if (osc_cpc_flexible_adr_space_confirmed &&
> -		   CPC_SUPPORTED(epp_set_reg) && CPC_IN_FFH(epp_set_reg)) {
> -		ret = cpc_write(cpu, epp_set_reg, perf_ctrls->energy_perf);
> +	} else if (osc_cpc_flexible_adr_space_confirmed) {

I had a comment in last version about the 
osc_cpc_flexible_adr_space_confirmed
handling. I don't know if it's still relevant:

https://lore.kernel.org/all/8fb77549-ce33-4c89-959b-57113eb716b6@arm.com/

> +		if (!epp_ffh_sysmem && !autosel_ffh_sysmem) {
> +			ret = -EOPNOTSUPP;
> +		} else {
> +			if (autosel_ffh_sysmem) {
> +				ret = cpc_write(cpu, auto_sel_reg, enable);
> +				if (ret)
> +					return ret;
> +			}
> +
> +			if (epp_ffh_sysmem) {
> +				ret = cpc_write(cpu, epp_set_reg,
> +						perf_ctrls->energy_perf);
> +				if (ret)
> +					return ret;
> +			}
> +		}
>   	} else {
> -		ret = -ENOTSUPP;
> -		pr_debug("_CPC in PCC and _CPC in FFH are not supported\n");
> +		ret = -EOPNOTSUPP;
>   	}
>   
> +	if (ret == -EOPNOTSUPP)
> +		pr_debug("CPU%d: _CPC not in PCC/FFH/SystemMemory\n", cpu);
> +
>   	return ret;
>   }
>   EXPORT_SYMBOL_GPL(cppc_set_epp_perf);
> @@ -1609,7 +1632,7 @@ EXPORT_SYMBOL_GPL(cppc_set_epp_perf);
>    */
>   int cppc_set_epp(int cpu, u64 epp_val)
>   {
> -	if (epp_val > CPPC_ENERGY_PERF_MAX)
> +	if (epp_val > CPPC_EPP_ENERGY_EFFICIENCY_PREF)
>   		return -EINVAL;
>   
>   	return cppc_set_reg_val(cpu, ENERGY_PERF, epp_val);
> diff --git a/include/acpi/cppc_acpi.h b/include/acpi/cppc_acpi.h
> index 12a1dc31bf2a..2860a0252313 100644
> --- a/include/acpi/cppc_acpi.h
> +++ b/include/acpi/cppc_acpi.h
> @@ -39,7 +39,8 @@
>   /* CPPC_AUTO_ACT_WINDOW_MAX_SIG is 127, so 128 and 129 will decay to 127 when writing */
>   #define CPPC_AUTO_ACT_WINDOW_SIG_CARRY_THRESH 129
>   
> -#define CPPC_ENERGY_PERF_MAX	(0xFF)
> +#define CPPC_EPP_PERFORMANCE_PREF		0x00
> +#define CPPC_EPP_ENERGY_EFFICIENCY_PREF		0xFF
>   
>   /* Each register has the folowing format. */
>   struct cpc_reg {