Currently there is a refcount leak in CTI when using system wide mode or tracing multithreaded applications. See the last commit for a reproducer. This prevents the module from being unloaded.
Historically there have been a few issues and fixes attempted around here which have resulted in some extra logic and a member to keep track of CTI being enabled 'struct coresight_device->ect_enabled'. The fix in commit 665c157e0204 ("coresight: cti: Fix hang in cti_disable_hw()") was also related to CTI having its own enable/disable path which came later than other devices.
If we make CTI a helper device and enable helper devices adjacent to the path we get very similar enable/disable behavior to now, but with more reuse of the existing reference counting logic in the coresight core code. This also affects CATU which can have a little bit of its hard coded enable/disable code removed.
Enabling CATU on the generic path does require that input connections are tracked so that it can get its associated ETR buffer.
Applies to coresight/next (669c4614236a7) but also requires the realloc_array patch here [1].
Also available in full here [2].
[1]: https://lore.kernel.org/linux-arm-kernel/20230306152723.3090195-1-james.clar... [2]: https://gitlab.arm.com/linux-arm/linux-jc/-/tree/james-cs-cti-module-refcoun...
James Clark (8): coresight: Use enum type for cs_mode wherever possible coresight: Change name of pdata->conns coresight: Rename nr_outports to nr_outconns coresight: Dynamically add connections coresight: Store in-connections as well as out-connections coresight: Refactor out buffer allocation function for ETR coresight: Enable and disable helper devices adjacent to the path coresight: Fix CTI module refcount leak by making it a helper device
drivers/hwtracing/coresight/coresight-catu.c | 34 ++- drivers/hwtracing/coresight/coresight-core.c | 258 +++++++++++------- .../hwtracing/coresight/coresight-cti-core.c | 56 ++-- .../hwtracing/coresight/coresight-cti-sysfs.c | 4 +- drivers/hwtracing/coresight/coresight-cti.h | 4 +- drivers/hwtracing/coresight/coresight-etb10.c | 3 +- .../coresight/coresight-etm3x-core.c | 6 +- .../coresight/coresight-etm4x-core.c | 6 +- .../hwtracing/coresight/coresight-platform.c | 168 +++++++++--- drivers/hwtracing/coresight/coresight-priv.h | 9 +- drivers/hwtracing/coresight/coresight-stm.c | 6 +- drivers/hwtracing/coresight/coresight-sysfs.c | 1 - .../hwtracing/coresight/coresight-tmc-etf.c | 2 +- .../hwtracing/coresight/coresight-tmc-etr.c | 88 +++--- drivers/hwtracing/coresight/coresight-tmc.h | 2 + drivers/hwtracing/coresight/coresight-tpdm.c | 4 +- drivers/hwtracing/coresight/coresight-tpiu.c | 3 +- drivers/hwtracing/coresight/coresight-trbe.c | 3 +- drivers/hwtracing/coresight/ultrasoc-smb.c | 3 +- drivers/hwtracing/coresight/ultrasoc-smb.h | 2 +- include/linux/coresight.h | 92 ++++--- 21 files changed, 483 insertions(+), 271 deletions(-)