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

Suzuki K Poulose
2025-12-18T09:32:17Z

Cc: Sudeep

On 18/12/2025 08:09, 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.
>
> 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.

Why ? AFAIU, we have ways to tie the power-domain to that of the cluster
and that can auto-magically keep the cluster power ON as long as you
want to use them.

Suzuki

>
> To address this, the series introduces:
> - Identifying cluster-bound devices via a new `qcom,cpu-bound-components`
> device tree property.
> - Implementing deferred probing: if associated CPUs are offline during
> probe, initialization is deferred until a CPU hotplug notifier detects
> the CPU coming online.
> - Utilizing `smp_call_function_single()` to ensure register accesses
> (initialization, enablement, sysfs reads) are always executed on a
> powered CPU within the target cluster.
> - Extending the CoreSight link `enable` callback to pass the `cs_mode`.
> This allows drivers to distinguish between SysFS and Perf modes and
> apply mode-specific logic.
>
> Jie Gan (1):
> arm64: dts: qcom: hamoa: add Coresight nodes for APSS debug block
>
> Yuanfang Zhang (11):
> dt-bindings: arm: coresight: Add 'qcom,cpu-bound-components' property
> coresight: Pass trace mode to link enable callback
> coresight-funnel: Support CPU cluster funnel initialization
> coresight-funnel: Defer probe when associated CPUs are offline
> coresight-replicator: Support CPU cluster replicator initialization
> coresight-replicator: Defer probe when associated CPUs are offline
> coresight-replicator: Update management interface for CPU-bound devices
> coresight-tmc: Support probe and initialization for CPU cluster TMCs
> coresight-tmc-etf: Refactor enable function for CPU cluster ETF support
> coresight-tmc: Update management interface for CPU-bound TMCs
> coresight-tmc: Defer probe when associated CPUs are offline
>
> Verification:
>
> This series has been verified on sm8750.
>
> Test steps for delay probe:
>
> 1. limit the system to enable at most 6 CPU cores during boot.
> 2. echo 1 >/sys/bus/cpu/devices/cpu6/online.
> 3. check whether ETM6 and ETM7 have been probed.
>
> Test steps for sysfs mode:
>
> echo 1 >/sys/bus/coresight/devices/tmc_etf0/enable_sink
> echo 1 >/sys/bus/coresight/devices/etm0/enable_source
> echo 1 >/sys/bus/coresight/devices/etm6/enable_source
> echo 0 >/sys/bus/coresight/devices/etm0/enable_source
> echo 0 >/sys/bus/coresight/devicse/etm6/enable_source
> echo 0 >/sys/bus/coresight/devices/tmc_etf0/enable_sink
>
> echo 1 >/sys/bus/coresight/devices/tmc_etf1/enable_sink
> echo 1 >/sys/bus/coresight/devcies/etm0/enable_source
> cat /dev/tmc_etf1 >/tmp/etf1.bin
> echo 0 >/sys/bus/coresight/devices/etm0/enable_source
> echo 0 >/sys/bus/coresight/devices/tmc_etf1/enable_sink
>
> echo 1 >/sys/bus/coresight/devices/tmc_etf2/enable_sink
> echo 1 >/sys/bus/coresight/devices/etm6/enable_source
> cat /dev/tmc_etf2 >/tmp/etf2.bin
> echo 0 >/sys/bus/coresight/devices/etm6/enable_source
> echo 0 >/sys/bus/coresight/devices/tmc_etf2/enable_sink
>
> Test steps for sysfs node:
>
> cat /sys/bus/coresight/devices/tmc_etf*/mgmt/*
>
> cat /sys/bus/coresight/devices/funnel*/funnel_ctrl
>
> cat /sys/bus/coresight/devices/replicator*/mgmt/*
>
> Test steps for perf mode:
>
> perf record -a -e cs_etm//k -- sleep 5
>
> Signed-off-by: Yuanfang Zhang <yuanfang.zhang@oss.qualcomm.com>
> ---
> Changes in v2:
> - Use the qcom,cpu-bound-components device tree property to identify devices
> bound to a cluster.
> - Refactor commit message.
> - Introduce a supported_cpus field in the drvdata structure to record the CPUs
> that belong to the cluster where the local component resides.
> - Link to v1: https://lore.kernel.org/r/20251027-cpu_cluster_component_pm-v1-0-31355ac588c2@oss.qualcomm.com
>
> ---
> Jie Gan (1):
> arm64: dts: qcom: hamoa: Add CoreSight nodes for APSS debug block
>
> Yuanfang Zhang (11):
> dt-bindings: arm: coresight: Add 'qcom,cpu-bound-components' property
> coresight-funnel: Support CPU cluster funnel initialization
> coresight-funnel: Defer probe when associated CPUs are offline
> coresight-replicator: Support CPU cluster replicator initialization
> coresight-replicator: Defer probe when associated CPUs are offline
> coresight-replicator: Update management interface for CPU-bound devices
> coresight-tmc: Support probe and initialization for CPU cluster TMCs
> coresight-tmc-etf: Refactor enable function for CPU cluster ETF support
> coresight-tmc: Update management interface for CPU-bound TMCs
> coresight-tmc: Defer probe when associated CPUs are offline
> coresight: Pass trace mode to link enable callback
>
> .../bindings/arm/arm,coresight-dynamic-funnel.yaml | 5 +
> .../arm/arm,coresight-dynamic-replicator.yaml | 5 +
> .../devicetree/bindings/arm/arm,coresight-tmc.yaml | 5 +
> arch/arm64/boot/dts/qcom/hamoa.dtsi | 926 +++++++++++++++++++++
> arch/arm64/boot/dts/qcom/purwa.dtsi | 12 +
> drivers/hwtracing/coresight/coresight-core.c | 7 +-
> drivers/hwtracing/coresight/coresight-funnel.c | 258 +++++-
> drivers/hwtracing/coresight/coresight-replicator.c | 341 +++++++-
> drivers/hwtracing/coresight/coresight-tmc-core.c | 387 +++++++--
> drivers/hwtracing/coresight/coresight-tmc-etf.c | 106 ++-
> drivers/hwtracing/coresight/coresight-tmc.h | 10 +
> drivers/hwtracing/coresight/coresight-tnoc.c | 3 +-
> drivers/hwtracing/coresight/coresight-tpda.c | 3 +-
> include/linux/coresight.h | 3 +-
> 14 files changed, 1902 insertions(+), 169 deletions(-)
> ---
> base-commit: 008d3547aae5bc86fac3eda317489169c3fda112
> change-id: 20251016-cpu_cluster_component_pm-ce518f510433
>
> Best regards,