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

[Suzuki K Poulose <suzuki.poulose@arm.com>]

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,