linux-kernel - Re: [PATCH v6 5/9] ACPI: CPPC: Extend cppc_set_epp

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Message-ID: <86303677-6124-424f-999d-c420eac0cceb@nvidia.com>
Date: Sun, 25 Jan 2026 01:38:02 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: "zhenglifeng (A)" <zhenglifeng1@...wei.com>
Cc: rafael@...nel.org, viresh.kumar@...aro.org, pierre.gondois@....com,
 ionela.voinescu@....com, lenb@...nel.org, robert.moore@...el.com,
 corbet@....net, rdunlap@...radead.org, ray.huang@....com,
 gautham.shenoy@....com, mario.limonciello@....com, perry.yuan@....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,
 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, sumitg@...dia.com
Subject: Re: [PATCH v6 5/9] ACPI: CPPC: Extend cppc_set_epp_perf() for
 FFH/SystemMemory


On 22/01/26 14:48, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> On 2026/1/20 22:56, 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.
>>
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
>> ---
>>   drivers/acpi/cppc_acpi.c | 24 +++++++++++++++++++++---
>>   1 file changed, 21 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
>> index de35aeb07833..45c6bd6ec24b 100644
>> --- a/drivers/acpi/cppc_acpi.c
>> +++ b/drivers/acpi/cppc_acpi.c
>> @@ -1562,6 +1562,8 @@ 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) {
>> @@ -1572,6 +1574,11 @@ 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);
>> @@ -1597,11 +1604,22 @@ int cppc_set_epp_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls, bool enable)
>>                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);
>> +                (epp_ffh_sysmem || autosel_ffh_sysmem)) {
>> +             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;
>> +             }
> Don't know if such a scenario exists, but if one of them is in PCC and the
> other is in FFH or system memory, only the one in PCC will be updated
> based on your modifications.
The current code handles mixed cases correctly.
When either register is in PCC, the first if block executes and calls
cpc_write() for both registers. The cpc_write() internally handles
each register's type (PCC, FFH, or SystemMemory)


Thank you,
Sumit Gupta



>>        } else {
>>                ret = -ENOTSUPP;
>> -             pr_debug("_CPC in PCC and _CPC in FFH are not supported\n");
>> +             pr_debug("_CPC in PCC/FFH/SystemMemory are not supported\n");
>>        }
>>
>>        return ret;