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

[Leo Yan]

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 at 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 at arm.com>