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b=iUE+6cnuHyVxGU0MssG2MLOjGfUeBqo7qBpVZO18Abwc5DPPgwBAX/kONhnt86OCCRdzcEz5arZKfts75iy2umfKpHiPChvPjzj2JkREbxzfMCjb73PhMg46cjoGlhmNrEt7T5DoTXZmOsZ8n0x34Sc2y50S2ZHYEfU9M+9ala8= Authentication-Results-Original: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=arm.com; Received: from VI0PR08MB10391.eurprd08.prod.outlook.com (2603:10a6:800:20c::6) by PAVPR08MB9329.eurprd08.prod.outlook.com (2603:10a6:102:305::19) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.9542.9; Mon, 26 Jan 2026 11:20:34 +0000 Received: from VI0PR08MB10391.eurprd08.prod.outlook.com ([fe80::fa6b:9ba8:5c2f:ac91]) by VI0PR08MB10391.eurprd08.prod.outlook.com ([fe80::fa6b:9ba8:5c2f:ac91%4]) with mapi id 15.20.9542.010; Mon, 26 Jan 2026 11:20:34 +0000 Message-ID: <3097e4dd-a895-4c55-96c7-433ae1d046f9@arm.com> Date: Mon, 26 Jan 2026 12:20:31 +0100 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 4/9] ACPI: CPPC: Add cppc_get_perf() API to read performance controls To: Sumit Gupta , "zhenglifeng (A)" Cc: rafael@kernel.org, viresh.kumar@linaro.org, ionela.voinescu@arm.com, lenb@kernel.org, robert.moore@intel.com, corbet@lwn.net, rdunlap@infradead.org, ray.huang@amd.com, gautham.shenoy@amd.com, mario.limonciello@amd.com, perry.yuan@amd.com, zhanjie9@hisilicon.com, linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, acpica-devel@lists.linux.dev, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, treding@nvidia.com, jonathanh@nvidia.com, vsethi@nvidia.com, ksitaraman@nvidia.com, sanjayc@nvidia.com, nhartman@nvidia.com, bbasu@nvidia.com References: <20260120145623.2959636-1-sumitg@nvidia.com> <20260120145623.2959636-5-sumitg@nvidia.com> <7f0b280d-9c22-46dc-a924-a85591e1034d@huawei.com> <53827af7-f3b6-4e1c-8c8d-2f57ef5be97e@nvidia.com> Content-Language: en-US From: Pierre Gondois In-Reply-To: <53827af7-f3b6-4e1c-8c8d-2f57ef5be97e@nvidia.com> Content-Type: text/plain; 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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 26 Jan 2026 11:21:38.2141 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: afd53b33-dbaa-47c7-0646-08de5ccd1299 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DB3PEPF0000885F.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI0PR08MB11017 On 1/24/26 21:19, Sumit Gupta wrote: > > On 25/01/26 01:35, Sumit Gupta wrote: >> >> On 22/01/26 14:26, zhenglifeng (A) wrote: >>> External email: Use caution opening links or attachments >>> >>> >>> On 2026/1/20 22:56, Sumit Gupta wrote: >>>> Add cppc_get_perf() function to read values of performance control >>>> registers including desired_perf, min_perf, max_perf, energy_perf, >>>> and auto_sel. >>>> >>>> This provides a read interface to complement the existing >>>> cppc_set_perf() write interface for performance control registers. >>>> >>>> Note that auto_sel is read by cppc_get_perf() but not written by >>>> cppc_set_perf() to avoid unintended mode changes during performance >>>> updates. It can be updated with existing dedicated cppc_set_auto_sel() >>>> API. >>>> >>>> Use cppc_get_perf() in cppc_cpufreq_get_cpu_data() to initialize >>>> perf_ctrls with current hardware register values during cpufreq >>>> policy initialization. >>>> >>>> Signed-off-by: Sumit Gupta >>>> --- >>>>   drivers/acpi/cppc_acpi.c       | 80 >>>> ++++++++++++++++++++++++++++++++++ >>>>   drivers/cpufreq/cppc_cpufreq.c |  6 +++ >>>>   include/acpi/cppc_acpi.h       |  5 +++ >>>>   3 files changed, 91 insertions(+) >>>> >>>> diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c >>>> index a09bdabaa804..de35aeb07833 100644 >>>> --- a/drivers/acpi/cppc_acpi.c >>>> +++ b/drivers/acpi/cppc_acpi.c >>>> @@ -1739,6 +1739,86 @@ int cppc_set_enable(int cpu, bool enable) >>>>   } >>>>   EXPORT_SYMBOL_GPL(cppc_set_enable); >>>> >>>> +/** >>>> + * cppc_get_perf - Get a CPU's performance controls. >>>> + * @cpu: CPU for which to get performance controls. >>>> + * @perf_ctrls: ptr to cppc_perf_ctrls. See cppc_acpi.h >>>> + * >>>> + * Return: 0 for success with perf_ctrls, -ERRNO otherwise. >>>> + */ >>>> +int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) >>>> +{ >>>> +     struct cpc_desc *cpc_desc = per_cpu(cpc_desc_ptr, cpu); >>>> +     struct cpc_register_resource *desired_perf_reg, >>>> +                                  *min_perf_reg, *max_perf_reg, >>>> +                                  *energy_perf_reg, *auto_sel_reg; >>>> +     u64 desired_perf = 0, min = 0, max = 0, energy_perf = 0, >>>> auto_sel = 0; >>>> +     int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu); >>>> +     struct cppc_pcc_data *pcc_ss_data = NULL; >>>> +     int ret = 0, regs_in_pcc = 0; >>>> + >>>> +     if (!cpc_desc) { >>>> +             pr_debug("No CPC descriptor for CPU:%d\n", cpu); >>>> +             return -ENODEV; >>>> +     } >>>> + >>>> +     if (!perf_ctrls) { >>>> +             pr_debug("Invalid perf_ctrls pointer\n"); >>>> +             return -EINVAL; >>>> +     } >>>> + >>>> +     desired_perf_reg = &cpc_desc->cpc_regs[DESIRED_PERF]; >>>> +     min_perf_reg = &cpc_desc->cpc_regs[MIN_PERF]; >>>> +     max_perf_reg = &cpc_desc->cpc_regs[MAX_PERF]; >>>> +     energy_perf_reg = &cpc_desc->cpc_regs[ENERGY_PERF]; >>>> +     auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE]; >>>> + >>>> +     /* Are any of the regs PCC ?*/ >>>> +     if (CPC_IN_PCC(desired_perf_reg) || CPC_IN_PCC(min_perf_reg) || >>>> +         CPC_IN_PCC(max_perf_reg) || CPC_IN_PCC(energy_perf_reg) || >>>> +         CPC_IN_PCC(auto_sel_reg)) { >>>> +             if (pcc_ss_id < 0) { >>>> +                     pr_debug("Invalid pcc_ss_id for CPU:%d\n", cpu); >>>> +                     return -ENODEV; >>>> +             } >>>> +             pcc_ss_data = pcc_data[pcc_ss_id]; >>>> +             regs_in_pcc = 1; >>>> +             down_write(&pcc_ss_data->pcc_lock); >>>> +             /* Ring doorbell once to update PCC subspace */ >>>> +             if (send_pcc_cmd(pcc_ss_id, CMD_READ) < 0) { >>>> +                     ret = -EIO; >>>> +                     goto out_err; >>>> +             } >>>> +     } >>>> + >>>> +     /* Read optional elements if present */ >>>> +     if (CPC_SUPPORTED(max_perf_reg)) >>>> +             cpc_read(cpu, max_perf_reg, &max); >>>> +     perf_ctrls->max_perf = max; >>>> + >>>> +     if (CPC_SUPPORTED(min_perf_reg)) >>>> +             cpc_read(cpu, min_perf_reg, &min); >>>> +     perf_ctrls->min_perf = min; >>>> + >>>> +     if (CPC_SUPPORTED(desired_perf_reg)) >>>> +             cpc_read(cpu, desired_perf_reg, &desired_perf); >>>> +     perf_ctrls->desired_perf = desired_perf; >>> desired_perf_reg is not an optional one, so it has to be supported. > > Please ignore my previous reply on this. Had some problem with my email > client and both mails got mixed. > > The register is optional when Autonomous mode is enabled. > Seems the comment here is already resolved with Pierre's reply. > We discussed this during v4 [1] also. > [1] > https://lore.kernel.org/lkml/ccd45c1b-2f69-4725-918f-18063f00a864@nvidia.com/ > > Thank you, > Sumit Gupta > > As suggested at: https://lore.kernel.org/all/5afea521-7d80-4e72-8809-77af60b0d957@arm.com/ Maybe it would be useful to add a patch checking this: diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index e3796b520e473..7db74e19425e6 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -854,6 +854,12 @@ int acpi_cppc_processor_probe(struct acpi_processor *pr)         }         per_cpu(cpu_pcc_subspace_idx, pr->id) = pcc_subspace_id; +       if (!CPC_SUPPORTED(&cpc_ptr->cpc_regs[DESIRED_PERF]) && +           (!osc_sb_cppc2_support_acked || + !CPC_SUPPORTED(&cpc_ptr->cpc_regs[AUTO_SEL_ENABLE]))) +               pr_warn("Desired perf. register is mandatory if CPPCV2 is not supported " +                       "or autonomous selection is disabled.\n"); +         /*          * Initialize the remaining cpc_regs as unsupported.          * Example: In case FW exposes CPPC v2, the below loop will initialize