[PATCH v11 19/27] coresight: etm4x: Set active path on target CPU

Leo Yan
2026-05-01T16:49:12Z

Set the path pointer on the target CPU during ETM enable and disable.

This ensures the device mode and path pointer are updated together and
observed atomically by the CPU PM notifier.

Tested-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
drivers/hwtracing/coresight/coresight-etm4x-core.c | 18 +++++++++++++++---
1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index bf29ecf487a6c57c67a31004a9911fffeba929f8..7c9e0af2f24556e27f6c1bcbb22044c52f13de12 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -234,6 +234,7 @@ void etm4_release_trace_id(struct etmv4_drvdata *drvdata)

struct etm4_enable_arg {
struct etmv4_drvdata *drvdata;
+ struct coresight_path *path;
int rc;
};

@@ -621,8 +622,12 @@ static void etm4_enable_sysfs_smp_call(void *info)
arg->rc = etm4_enable_hw(arg->drvdata);

/* The tracer didn't start */
- if (arg->rc)
+ if (arg->rc) {
coresight_set_mode(csdev, CS_MODE_DISABLED);
+ return;
+ }
+
+ csdev->path = arg->path;
}

/*
@@ -890,9 +895,13 @@ static int etm4_enable_perf(struct coresight_device *csdev,

out:
/* Failed to start tracer; roll back to DISABLED mode */
- if (ret)
+ if (ret) {
coresight_set_mode(csdev, CS_MODE_DISABLED);
- return ret;
+ return ret;
+ }
+
+ csdev->path = path;
+ return 0;
}

static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_path *path)
@@ -922,6 +931,7 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa
* ensures that register writes occur when cpu is powered.
*/
arg.drvdata = drvdata;
+ arg.path = path;
ret = smp_call_function_single(drvdata->cpu,
etm4_enable_sysfs_smp_call, &arg, 1);
if (!ret)
@@ -1063,6 +1073,7 @@ static void etm4_disable_sysfs_smp_call(void *info)

etm4_disable_hw(drvdata);

+ drvdata->csdev->path = NULL;
coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
}

@@ -1092,6 +1103,7 @@ static int etm4_disable_perf(struct coresight_device *csdev,
/* TRCVICTLR::SSSTATUS, bit[9] */
filters->ssstatus = (control & BIT(9));

+ drvdata->csdev->path = NULL;
coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);

/*

--
2.34.1