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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-7ff7af2b537sm623722b3a.20.2025.12.18.18.13.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 18 Dec 2025 18:13:20 -0800 (PST) Message-ID: Date: Fri, 19 Dec 2025 10:13:14 +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: [PATCH v2 00/12] coresight: Add CPU cluster funnel/replicator/tmc support To: Sudeep Holla Cc: Suzuki K Poulose , Mike Leach , James Clark , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Mathieu Poirier , Leo Yan , Alexander Shishkin , Bjorn Andersson , Konrad Dybcio , kernel@oss.qualcomm.com, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, maulik.shah@oss.qualcomm.com, Jie Gan References: <20251218-cpu_cluster_component_pm-v2-0-2335a6ae62a0@oss.qualcomm.com> <20251218-careful-ruby-wildebeest-a8babd@sudeepholla> Content-Language: en-US From: yuanfang zhang In-Reply-To: <20251218-careful-ruby-wildebeest-a8babd@sudeepholla> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Proofpoint-GUID: vYWYjwnWaLqysm8DfLn2mrPIOUM-W49k X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjE5MDAxNiBTYWx0ZWRfX0sOwkIXoq3e9 gOg7I32R3PAZ2SDgeFxM2k5SQ/ML8w978KaEoczTtca5SvkYgay06z+R+a4AcRO7MevpaXJ3UAc isOGGoA44taJq23Paqnj+2oEjaE2prGPIW4A4hGx9ZVr0cQKP5L++TS+wLkArapyhcBnsLrl1ux YiX1LJ/uoH5vQLpmsNM6SEiDAflhyjY/Gh/e6ymfjPeXLjxhuDD1/fXFHNIVFLierr3on01RlFL a6jbEh/cx/fZtkKOe5+TEO3/+thfVIuMpJJm1CJPrWgYbS1IO4sUo1wKNZBkublZhbhF1NdSO9j 57YNRZgL7K8+lP65wrKezzDD7JrON/L6n1t4ezQUed5Bqvur8AF9PKI0LAo8LKcpAv9LBcbz9sW zYDidoE4ykbD22ch1FRgWBE7gYObzRQOZQc9tmQNiIdMB0UedCbLfHkkf3VRtuPXmG1+NNOwWfF PVud17+PpEBiy7iyVQQ== X-Authority-Analysis: v=2.4 cv=feSgCkQF c=1 sm=1 tr=0 ts=6944b4c1 cx=c_pps a=mDZGXZTwRPZaeRUbqKGCBw==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=CT3mT5stn3mpJVhV_EcA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=zc0IvFSfCIW2DFIPzwfm:22 X-Proofpoint-ORIG-GUID: vYWYjwnWaLqysm8DfLn2mrPIOUM-W49k X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-19_01,2025-12-17_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 priorityscore=1501 malwarescore=0 suspectscore=0 spamscore=0 lowpriorityscore=0 adultscore=0 bulkscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2512120000 definitions=main-2512190016 On 12/18/2025 7:33 PM, Sudeep Holla wrote: > On Thu, Dec 18, 2025 at 12:09:40AM -0800, Yuanfang Zhang wrote: >> This patch series adds support for CoreSight components local to CPU clusters, >> including funnel, replicator, and TMC, which reside within CPU cluster power >> domains. These components require special handling due to power domain >> constraints. >> > > Could you clarify why PSCI-based power domains associated with clusters in > domain-idle-states cannot address these requirements, given that PSCI CPU-idle > OSI mode was originally intended to support them? My understanding of this > patch series is that OSI mode is unable to do so, which, if accurate, appears > to be a flaw that should be corrected. It is due to the particular characteristics of the CPU cluster power domain.Runtime PM for CPU devices works little different, it is mostly used to manage hierarchical CPU topology (PSCI OSI mode) to talk with genpd framework to manage the last CPU handling in cluster. It doesn’t really send IPI to wakeup CPU device (It don’t have .power_on/.power_off) callback implemented which gets invoked from .runtime_resume callback. This behavior is aligned with the upstream Kernel. > >> Unlike system-level CoreSight devices, these components share the CPU cluster's >> power domain. When the cluster enters low-power mode (LPM), their registers >> become inaccessible. Notably, `pm_runtime_get` alone cannot bring the cluster >> out of LPM, making standard register access unreliable. >> > > Are these devices the only ones on the system that are uniquely bound to > cluster-level power domains? If not, what additional devices share this > dependency so that we can understand how they are managed in comparison? > Yes, devices like ETM and TRBE also share this power domain and access constraint. Their drivers naturally handle enablement/disablement on the specific CPU they belong to (e.g., via hotplug callbacks or existing smp_call_function paths). >> To address this, the series introduces: >> - Identifying cluster-bound devices via a new `qcom,cpu-bound-components` >> device tree property. > > Really, no please. > Our objective is to determine which CoreSight components are physically locate within the CPU cluster power domain. Would it be acceptable to derive this relationship from the existing power-domains binding? For example, if a Funnel or Replicator node is linked to a power-domains entry that specifies a cpumask, the driver could recognize this shared dependency and automatically apply the appropriate cluster-aware behavior. thanks, yuanfang.