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Message-ID: <4fa3d3bb-9853-4041-9db1-3d9728cbff44@nvidia.com>
Date: Thu, 8 Jan 2026 19:09:32 +0530
From: Sumit Gupta <sumitg@...dia.com>
To: "zhenglifeng (A)" <zhenglifeng1@...wei.com>, rafael@...nel.org,
viresh.kumar@...aro.org, lenb@...nel.org, robert.moore@...el.com,
corbet@....net, pierre.gondois@....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, sumitg@...dia.com
Subject: Re: [PATCH v5 04/11] ACPI: CPPC: Extend cppc_set_epp_perf() to
support auto_sel and epp
On 25/12/25 09:26, zhenglifeng (A) wrote:
> External email: Use caution opening links or attachments
>
>
> On 2025/12/23 20:13, 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) {
>> + if (!epp_ffh_sysmem && !autosel_ffh_sysmem) {
>> + ret = -EOPNOTSUPP;
>> + } else {
> I think this can do the same thing:
>
> } else if (osc_cpc_flexible_adr_space_confirmed &&
> (epp_ffh_sysmem || autosel_ffh_sysmem)) {
>
> and reduce the levels of indentation.
Thanks for suggesting. Will change in v6.
>> + 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);
> The code below is unrelated to the code above and should ideally be
> separated into a separate patch I think.
Will move it to a separate patch in v6.
Thank you,
Sumit Gupta
>
>> @@ -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 {
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