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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-84edc29ebeasm449580b3a.30.2026.07.31.06.19.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 31 Jul 2026 06:19:34 -0700 (PDT) Message-ID: Date: Fri, 31 Jul 2026 21:19:15 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCHv2 3/3] ACPI: CPPC: Stop reading desired_perf in cppc_get_perf() To: Christian Loehle , "Rafael J . Wysocki" , Viresh Kumar Cc: linux-pm@vger.kernel.org, linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Len Brown , Jie Zhan , Lifeng Zheng , Pierre Gondois , Sumit Gupta , Sudeep Holla , Ionela Voinescu , zhongqiu.han@oss.qualcomm.com References: <20260729100245.2628302-1-christian.loehle@arm.com> <20260729100245.2628302-4-christian.loehle@arm.com> Content-Language: en-US From: Zhongqiu Han In-Reply-To: <20260729100245.2628302-4-christian.loehle@arm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzMxMDEwMSBTYWx0ZWRfX7uFRLI7rz4Yu agzErTsbfKk3gYfP1a7hF8Vc5Yal5IQw73OwTdkvsQwx+GAEPuR9mSqZNpnM6QeqcNFFqPntSwz CWfDLJMqTwI5RpFG4DODEopZzEJFSrVWfu9AlDUCagJ8UyygBMJRyNyJoAayNZetx/lF6r9sVgz i7OQtWx5MRTtq9kubCtvMb0lrpJSUWuUK2vgTmsWE1EAqNp8vDEItzfBRThN/sDnrtvUoUbiwjr A97XeJYCjjIKohNpW5r6fCPmuk+A4MWSt1aDLZ8iZEaSNtCQzAcduEfb76yJMzxOODZRHtu00tm ukkOnxMbwacU+7L8tRnpplmY6crI3YY34XteLMrEqaeQn2lLv1bXk23qxw9T2NMDiXB6hHjI9qJ FX0TgUnKNnovfrRdKVCeT+qJ9Tj9PXDD+2vkTURWz8QfgBDO69+GwFwgVm6H7HArZQpY+1lve8F ZH8URfBpX+t6f9a0z3g== X-Proofpoint-ORIG-GUID: 55xnpwYs7hHfyZgyHNti4KypV2dvKPZJ X-Proofpoint-Spam-Info: AW1haW4tMjYwNzMxMDEwMSBTYWx0ZWRfX9jCEcxDJjJB5 /rtf3whiK656HfDfXc+HIHdLyhWSwYVOYO87MnFuY+5XCi3djONd+E6E4LCrfFhX6t2bhLzL5wW dHOk47wLvMnwGtCSKaiHPCltIoNmZFg= X-Authority-Analysis: v=2.4 cv=YaGNIQRf c=1 sm=1 tr=0 ts=6a6ca0e7 cx=c_pps a=Qgeoaf8Lrialg5Z894R3/Q==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yx91gb_oNiZeI1HMLzn7:22 a=7CQSdrXTAAAA:8 a=EUspDBNiAAAA:8 a=It08kXP3PLQ7WbTW8E4A:9 a=QEXdDO2ut3YA:10 a=x9snwWr2DeNwDh03kgHS:22 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-GUID: 55xnpwYs7hHfyZgyHNti4KypV2dvKPZJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-31_04,2026-07-30_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 malwarescore=0 priorityscore=1501 suspectscore=0 bulkscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607310101 On 7/29/2026 6:02 PM, Christian Loehle wrote: > cppc_get_perf() has one in-tree caller, cppc_cpufreq_get_cpu_data(). > It uses the function to preserve existing controls before writing them, but > overwrites desired_perf with highest_perf before the first cppc_set_perf(). > Consequently, the current Desired Performance value is not consumed. > > Remove the Desired Performance read from this aggregate getter and > document that the field is returned as zero. > > Signed-off-by: Christian Loehle > --- > drivers/acpi/cppc_acpi.c | 23 ++++++++--------------- > 1 file changed, 8 insertions(+), 15 deletions(-) > > diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c > index 210988d57b71..8ce2033ba993 100644 > --- a/drivers/acpi/cppc_acpi.c > +++ b/drivers/acpi/cppc_acpi.c > @@ -1828,22 +1828,22 @@ int cppc_set_enable(int cpu, bool enable) > EXPORT_SYMBOL_GPL(cppc_set_enable); > > /** > - * cppc_get_perf - Get a CPU's performance controls. > + * cppc_get_perf - Get a CPU's readable performance controls. Small nit: is this also applicable to ACPI <6.6? > * @cpu: CPU for which to get performance controls. > * @perf_ctrls: ptr to cppc_perf_ctrls. See cppc_acpi.h > * > + * Desired Performance is not read and is returned as 0. Likewise. > + * > * 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, > + struct cpc_register_resource *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; > + u64 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; > - bool read_desired_perf = cppc_desired_perf_readable(); > int ret = 0, regs_in_pcc = 0; > > if (!cpc_desc) { > @@ -1856,16 +1856,14 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) > 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 ((read_desired_perf && CPC_IN_PCC(desired_perf_reg)) || > - CPC_IN_PCC(min_perf_reg) || > - CPC_IN_PCC(max_perf_reg) || CPC_IN_PCC(energy_perf_reg) || > + if (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); > @@ -1896,12 +1894,7 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) > } > perf_ctrls->min_perf = min; > > - if (read_desired_perf && CPC_SUPPORTED(desired_perf_reg)) { > - ret = cpc_read(cpu, desired_perf_reg, &desired_perf); > - if (ret) > - goto out_err; > - } > - perf_ctrls->desired_perf = desired_perf; > + perf_ctrls->desired_perf = 0; > > if (CPC_SUPPORTED(energy_perf_reg)) { > ret = cpc_read(cpu, energy_perf_reg, &energy_perf); This is an exported API, I'm not sure whether this would break any out of-tree users, but I don't think compatibility concerns for out-of-tree users should weigh heavily in this case. Looks good to me. Reviewed-by: Zhongqiu Han -- Thx and BRs, Zhongqiu Han