[PATCH v11 15/27] coresight: Control path with range

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

Add parameters @from and @to for path enabling and disabling, allowing
finer-grained control of a path. The range is [@from..@to], where both
@from and @to are inclusive, introduce coresight_path_nodes_in_order()
to validate the given range if is ordered.

The helpers coresight_path_{first|last}_node() are provided for
conveniently fetching the first and last nodes on the path.

A minor refactoring removes the local variable "source" from
coresight_enable_path_from_to(), deferring reading the source until it
is needed.

Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
drivers/hwtracing/coresight/coresight-core.c | 100 ++++++++++++++++++++++-----
1 file changed, 82 insertions(+), 18 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 6ab80ae7c389e9031d4ab065d83bb676fd12160b..46b6447ce527b4c30d3f0d57801257f90580cc12 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -62,6 +62,24 @@ static LIST_HEAD(coresight_dev_idx_list);

static const struct cti_assoc_op *cti_assoc_ops;

+static struct coresight_node *
+coresight_path_first_node(struct coresight_path *path)
+{
+ if (list_empty(&path->path_list))
+ return NULL;
+
+ return list_first_entry(&path->path_list, struct coresight_node, link);
+}
+
+static struct coresight_node *
+coresight_path_last_node(struct coresight_path *path)
+{
+ if (list_empty(&path->path_list))
+ return NULL;
+
+ return list_last_entry(&path->path_list, struct coresight_node, link);
+}
+
void coresight_set_cti_ops(const struct cti_assoc_op *cti_op)
{
cti_assoc_ops = cti_op;
@@ -479,19 +497,46 @@ int coresight_resume_source(struct coresight_device *csdev)
EXPORT_SYMBOL_GPL(coresight_resume_source);

/*
- * coresight_disable_path_from : Disable components in the given path starting
- * from @nd in the list. If @nd is NULL, all the components, except the SOURCE
- * are disabled.
+ * Callers must fetch nodes from the path and pass @from and @to to the path
+ * enable/disable functions. Walk the path from @from to locate @to. If @to
+ * is found, it indicates @from and @to are in order. Otherwise, they are out
+ * of order.
+ */
+static bool coresight_path_nodes_in_order(struct coresight_path *path,
+ struct coresight_node *from,
+ struct coresight_node *to)
+{
+ struct coresight_node *nd;
+
+ if (WARN_ON_ONCE(!from || !to))
+ return false;
+
+ nd = from;
+ list_for_each_entry_from(nd, &path->path_list, link) {
+ if (nd == to)
+ return true;
+ }
+
+ return false;
+}
+
+/*
+ * coresight_disable_path_from_to: Disable components in the given path from
+ * @from to @to (inclusive) in the list. If both @from and @to are NULL, all
+ * the components, except the SOURCE are disabled.
*/
-static void coresight_disable_path_from(struct coresight_path *path,
- struct coresight_node *nd)
+static void coresight_disable_path_from_to(struct coresight_path *path,
+ struct coresight_node *from,
+ struct coresight_node *to)
{
u32 type;
struct coresight_device *csdev, *parent, *child;
+ struct coresight_node *nd;

- if (!nd)
- nd = list_first_entry(&path->path_list, struct coresight_node, link);
+ if (!coresight_path_nodes_in_order(path, from, to))
+ return;

+ nd = from;
list_for_each_entry_from(nd, &path->path_list, link) {
csdev = nd->csdev;
type = csdev->type;
@@ -525,12 +570,18 @@ static void coresight_disable_path_from(struct coresight_path *path,

/* Disable all helpers adjacent along the path last */
coresight_disable_helpers(csdev, path);
+
+ /* Iterate up to and including @to */
+ if (nd == to)
+ break;
}
}

void coresight_disable_path(struct coresight_path *path)
{
- coresight_disable_path_from(path, NULL);
+ coresight_disable_path_from_to(path,
+ coresight_path_first_node(path),
+ coresight_path_last_node(path));
}
EXPORT_SYMBOL_GPL(coresight_disable_path);

@@ -563,19 +614,20 @@ static int coresight_enable_helpers(struct coresight_device *csdev,
return ret;
}

-int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
+static int coresight_enable_path_from_to(struct coresight_path *path,
+ enum cs_mode mode,
+ struct coresight_node *from,
+ struct coresight_node *to)
{
int ret = 0;
u32 type;
- struct coresight_node *nd, *last;
+ struct coresight_node *nd;
struct coresight_device *csdev, *parent, *child;
- struct coresight_device *source;
-
- source = coresight_get_source(path);

- last = list_last_entry(&path->path_list, struct coresight_node, link);
+ if (!coresight_path_nodes_in_order(path, from, to))
+ return -EINVAL;

- nd = last;
+ nd = to;
list_for_each_entry_from_reverse(nd, &path->path_list, link) {
csdev = nd->csdev;
type = csdev->type;
@@ -615,7 +667,8 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
case CORESIGHT_DEV_TYPE_LINK:
parent = list_prev_entry(nd, link)->csdev;
child = list_next_entry(nd, link)->csdev;
- ret = coresight_enable_link(csdev, parent, child, source);
+ ret = coresight_enable_link(csdev, parent, child,
+ coresight_get_source(path));
if (ret)
goto err_disable_helpers;
break;
@@ -623,6 +676,10 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
ret = -EINVAL;
goto err_disable_helpers;
}
+
+ /* Iterate down to and including @from */
+ if (nd == from)
+ break;
}

out:
@@ -631,14 +688,21 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
coresight_disable_helpers(csdev, path);
err_disable_path:
/* No device is actually enabled */
- if (nd == last)
+ if (nd == to)
goto out;

nd = list_next_entry(nd, link);
- coresight_disable_path_from(path, nd);
+ coresight_disable_path_from_to(path, nd, to);
goto out;
}

+int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
+{
+ return coresight_enable_path_from_to(path, mode,
+ coresight_path_first_node(path),
+ coresight_path_last_node(path));
+}
+
struct coresight_device *coresight_get_sink(struct coresight_path *path)
{
struct coresight_device *csdev;

--
2.34.1