linux-kernel - Re: [PATCH v2 00/12] coresight: Add CPU cluster funnel/replicator/tmc support

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Message-ID: <20251218-careful-ruby-wildebeest-a8babd@sudeepholla>
Date: Thu, 18 Dec 2025 11:33:05 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Yuanfang Zhang <yuanfang.zhang@....qualcomm.com>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Mike Leach <mike.leach@...aro.org>,
	James Clark <james.clark@...aro.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Leo Yan <leo.yan@...ux.dev>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>, kernel@....qualcomm.com,
	coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, maulik.shah@....qualcomm.com,
	Jie Gan <jie.gan@....qualcomm.com>
Subject: Re: [PATCH v2 00/12] coresight: Add CPU cluster
 funnel/replicator/tmc support

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.

> 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?

> To address this, the series introduces:
> - Identifying cluster-bound devices via a new `qcom,cpu-bound-components`
>   device tree property.

Really, no please.

-- 
Regards,
Sudeep