[PATCH v11 08/27] coresight: Move per-CPU source pointer to core layer

[Leo Yan]

Move the per-CPU source pointer from ETM perf to the core layer, as this
will be used for not only perf session and also for CPU PM notifiers.

Provides coresight_{set|clear|get}_percpu_source() helpers to access the
per-CPU source pointer. Add a raw spinlock to protect exclusive access.

Device registration and unregistration call the set and clear helpers
for init and teardown the pointers.

Update callers to invoke coresight_get_percpu_source() for retrieving
the pointer.

Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c     | 38 ++++++++++++++++++++++++
 drivers/hwtracing/coresight/coresight-etm-perf.c | 14 +++------
 drivers/hwtracing/coresight/coresight-priv.h     |  1 +
 3 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 1a389f63ed006e054dc6bc9764f8be8c1def9da1..6da15f2ef9dc9770e7aa79cc94a7ed3d2f3ad871 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -35,6 +35,9 @@
 DEFINE_MUTEX(coresight_mutex);
 static DEFINE_PER_CPU(struct coresight_device *, csdev_sink);
 
+static DEFINE_RAW_SPINLOCK(coresight_dev_lock);
+static DEFINE_PER_CPU(struct coresight_device *, csdev_source);
+
 /**
  * struct coresight_node - elements of a path, from source to sink
  * @csdev:	Address of an element.
@@ -82,6 +85,39 @@ struct coresight_device *coresight_get_percpu_sink(int cpu)
 }
 EXPORT_SYMBOL_GPL(coresight_get_percpu_sink);
 
+static void coresight_set_percpu_source(struct coresight_device *csdev)
+{
+	if (!csdev || !coresight_is_percpu_source(csdev))
+		return;
+
+	guard(raw_spinlock_irqsave)(&coresight_dev_lock);
+
+	/* Expect no device to be set yet */
+	WARN_ON(per_cpu(csdev_source, csdev->cpu));
+	per_cpu(csdev_source, csdev->cpu) = csdev;
+}
+
+static void coresight_clear_percpu_source(struct coresight_device *csdev)
+{
+	if (!csdev || !coresight_is_percpu_source(csdev))
+		return;
+
+	guard(raw_spinlock_irqsave)(&coresight_dev_lock);
+
+	/* The per-CPU pointer should contain the same csdev */
+	WARN_ON(per_cpu(csdev_source, csdev->cpu) != csdev);
+	per_cpu(csdev_source, csdev->cpu) = NULL;
+}
+
+struct coresight_device *coresight_get_percpu_source(int cpu)
+{
+	if (WARN_ON(cpu < 0))
+		return NULL;
+
+	guard(raw_spinlock_irqsave)(&coresight_dev_lock);
+	return per_cpu(csdev_source, cpu);
+}
+
 struct coresight_device *coresight_get_source(struct coresight_path *path)
 {
 	struct coresight_device *csdev;
@@ -1436,6 +1472,7 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 	if (ret)
 		goto out_unlock;
 
+	coresight_set_percpu_source(csdev);
 	mutex_unlock(&coresight_mutex);
 
 	if (cti_assoc_ops && cti_assoc_ops->add)
@@ -1465,6 +1502,7 @@ void coresight_unregister(struct coresight_device *csdev)
 		cti_assoc_ops->remove(csdev);
 
 	mutex_lock(&coresight_mutex);
+	coresight_clear_percpu_source(csdev);
 	etm_perf_del_symlink_sink(csdev);
 	coresight_remove_conns(csdev);
 	coresight_clear_default_sink(csdev);
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index ca250d626db8ff89682fcb78e35a246cbd0ae367..d3b13ef130439fd501f88395d0de9dd21b84b827 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -49,7 +49,6 @@ struct etm_ctxt {
 };
 
 static DEFINE_PER_CPU(struct etm_ctxt, etm_ctxt);
-static DEFINE_PER_CPU(struct coresight_device *, csdev_src);
 
 GEN_PMU_FORMAT_ATTR(cycacc);
 GEN_PMU_FORMAT_ATTR(timestamp);
@@ -380,7 +379,7 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		struct coresight_path *path;
 		struct coresight_device *csdev;
 
-		csdev = per_cpu(csdev_src, cpu);
+		csdev = coresight_get_percpu_source(cpu);
 		/*
 		 * If there is no ETM associated with this CPU clear it from
 		 * the mask and continue with the rest. If ever we try to trace
@@ -856,17 +855,12 @@ int etm_perf_symlink(struct coresight_device *csdev, bool link)
 	if (!etm_perf_up)
 		return -EPROBE_DEFER;
 
-	if (link) {
+	if (link)
 		ret = sysfs_create_link(&pmu_dev->kobj, &cs_dev->kobj, entry);
-		if (ret)
-			return ret;
-		per_cpu(csdev_src, cpu) = csdev;
-	} else {
+	else
 		sysfs_remove_link(&pmu_dev->kobj, entry);
-		per_cpu(csdev_src, cpu) = NULL;
-	}
 
-	return 0;
+	return ret;
 }
 EXPORT_SYMBOL_GPL(etm_perf_symlink);
 
diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index a0cd1a0ad2a182f762cc9721fd93725f2d4ef688..7ce79fa36232bb1b0af768423777bab27cacee95 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -249,6 +249,7 @@ void coresight_add_helper(struct coresight_device *csdev,
 void coresight_set_percpu_sink(int cpu, struct coresight_device *csdev);
 struct coresight_device *coresight_get_percpu_sink(int cpu);
 struct coresight_device *coresight_get_source(struct coresight_path *path);
+struct coresight_device *coresight_get_percpu_source(int cpu);
 void coresight_disable_source(struct coresight_device *csdev, void *data);
 void coresight_pause_source(struct coresight_device *csdev);
 int coresight_resume_source(struct coresight_device *csdev);

-- 
2.34.1