[PATCH v11 00/27] CoreSight: Refactor power management for CoreSight path

Leo Yan
2026-05-01T16:48:18Z

This series focuses on CoreSight path power management. The changes can
be divided into four parts for review:

Patches 01 - 09: Preparison for CPU PM:
Fix helper enable failure handling.
Refactor CPU ID stored in csdev.
Move CPU lock to sysfs layer.
Move per-CPU source pointer from etm-perf to core layer.
Refactor etm-perf to retrieve source via per-CPU's event
data for lockless and get source reference during AUX
setup.
Patches 10 - 12: Refactor CPU idle flow managed in the CoreSight core
layer.
Patches 13 - 22: Refactor path enable / disable with range, control path
during CPU idle.
Patches 23 - 24: Support the sink (TRBE) control during CPU idle.
Patches 25 - 27: Move CPU hotplug into the core layer, and fix sysfs
mode for hotplug.

This series is rebased on the coresight-next branch and has been verified
on Juno-r2 (ETM + ETR) and FVP RevC (ETE + TRBE). Built successfully
for armv7 (ARCH=arm).

---
Changes in v11:
- Moved per-CPU source pointer from etm-perf to core (Suzuki).
- Added grabbing/ungrabbing csdev for device reference (Suzuki).
- Minor refine for error handling and logs in CPU PM (James).
- Refactored etm-perf with fetching path/source from event data (Suzuki).
- Fixed Helper error handling (sashiko).
- Added Jie's test tag (thanks!).
- Minor improvement for comments and commit logs.
- Link to v10: https://lore.kernel.org/r/20260405-arm_coresight_path_power_management_improvement-v10-0-13e94754a8be@arm.com

Changes in v10:
- Removed redundant checks in ETMv4 PM callbacks (sashiko).
- Added a new const structure etm4_cs_pm_ops (sashiko).
- Used fine-grained spinlock on sysfs_active_config (sashiko).
- Blocked notification after failures in save / restore to avoid lockups.
- Changed Change CPUHP_AP_ARM_CORESIGHT_STARTING to
CPUHP_AP_ARM_CORESIGHT_ONLINE so that the CPU hotplug callback runs in
the thread context (sashiko).
- Link to v9: https://lore.kernel.org/r/20260401-arm_coresight_path_power_management_improvement-v9-0-091d73e44072@arm.com

Changes in v9:
- Changed to use per-CPU path pointer with lockless access.
- Removed the change for adding csdev->path, the related refactoring
will be sent separately.
- Re-orged patches to avoid intermediate breakage (sashiko).
- Link to v8: https://lore.kernel.org/r/20260325-arm_coresight_path_power_management_improvement-v8-0-7b1902e18041@arm.com

Changes in v8:
- Moved the "cpu" field in coresight_device for better pack with new
patch 01 (Suzuki).
- Added check if not set CPU for per_cpu_source/per_cpu_sink (Suzuki).
- Renamed spinlock name in syscfg (Suzuki).
- Refactored paired enable and disable path with new patches
10 and 12 (Suzuki).
- Link to v7: https://lore.kernel.org/r/20260320-arm_coresight_path_power_management_improvement-v7-0-327ddd36b58b@arm.com

Signed-off-by: Leo Yan <leo.yan@arm.com>

---
Leo Yan (26):
coresight: Handle helper enable failure properly
coresight: Extract device init into coresight_init_device()
coresight: Populate CPU ID into coresight_device
coresight: Remove .cpu_id() callback from source ops
coresight: Take hotplug lock in enable_source_store() for Sysfs mode
coresight: perf: Retrieve path and source from event data
coresight: Take a reference on csdev
coresight: Move per-CPU source pointer to core layer
coresight: Grab per-CPU source device during AUX setup
coresight: Register CPU PM notifier in core layer
coresight: etm4x: Hook CPU PM callbacks
coresight: etm4x: Remove redundant checks in PM save and restore
coresight: syscfg: Use IRQ-safe spinlock to protect active variables
coresight: Move source helper disabling to coresight_disable_path()
coresight: Control path with range
coresight: Use helpers to fetch first and last nodes
coresight: Introduce coresight_enable_source() helper
coresight: Save active path for system tracers
coresight: etm4x: Set active path on target CPU
coresight: etm3x: Set active path on target CPU
coresight: sysfs: Use source's path pointer for path control
coresight: Control path during CPU idle
coresight: Add PM callbacks for sink device
coresight: sysfs: Increment refcount only for system tracers
coresight: Move CPU hotplug callbacks to core layer
coresight: sysfs: Validate CPU online status for per-CPU sources

Yabin Cui (1):
coresight: trbe: Save and restore state across CPU low power state

drivers/hwtracing/coresight/coresight-catu.c | 2 +-
drivers/hwtracing/coresight/coresight-core.c | 530 ++++++++++++++++++---
drivers/hwtracing/coresight/coresight-cti-core.c | 9 +-
drivers/hwtracing/coresight/coresight-etm-perf.c | 268 ++++++-----
drivers/hwtracing/coresight/coresight-etm3x-core.c | 73 +--
drivers/hwtracing/coresight/coresight-etm4x-core.c | 166 ++-----
drivers/hwtracing/coresight/coresight-priv.h | 6 +
drivers/hwtracing/coresight/coresight-syscfg.c | 38 +-
drivers/hwtracing/coresight/coresight-syscfg.h | 2 +
drivers/hwtracing/coresight/coresight-sysfs.c | 133 ++----
drivers/hwtracing/coresight/coresight-trbe.c | 61 ++-
include/linux/coresight.h | 15 +-
include/linux/cpuhotplug.h | 2 +-
13 files changed, 833 insertions(+), 472 deletions(-)
---
base-commit: 971f3474f8898ae8bbab19a9b547819a5e6fbcf1
change-id: 20251104-arm_coresight_path_power_management_improvement-dab4966f8280

Best regards,
--
Leo Yan <leo.yan@arm.com>