[PATCH v11 14/27] coresight: Move source helper disabling to coresight_disable_path()

[Leo Yan]

Move source helper disabling to coresight_disable_path() to pair it with
coresight_enable_path().

In coresight_enable_path(), if enabling a node fails, iterate to the
next node (which is the last successfully enabled node) and pass it to
coresight_disable_path() for rollback.  If the failed node is the last
node on the path, no device is actually enabled, so bail out directly.

As a result, coresight_disable_source() only controls the source,
leaving the associated helpers to be managed as part of path.  Update
the comment to reflect this change.

Tested-by: Jie Gan <jie.gan at oss.qualcomm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun at arm.com>
Reviewed-by: James Clark <james.clark at linaro.org>
Tested-by: James Clark <james.clark at linaro.org>
Signed-off-by: Leo Yan <leo.yan at arm.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 38 +++++++++++++---------------
 1 file changed, 17 insertions(+), 21 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 0c11e7fff1bd5cf504b17241595d83a1d11bcf40..6ab80ae7c389e9031d4ab065d83bb676fd12160b 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -447,19 +447,12 @@ static void coresight_disable_helpers(struct coresight_device *csdev,
 }
 
 /*
- * Helper function to call source_ops(csdev)->disable and also disable the
- * helpers.
- *
- * There is an imbalance between coresight_enable_path() and
- * coresight_disable_path(). Enabling also enables the source's helpers as part
- * of the path, but disabling always skips the first item in the path (which is
- * the source), so sources and their helpers don't get disabled as part of that
- * function and we need the extra step here.
+ * coresight_disable_source() only disables the source, but do nothing for
+ * the associated helpers, which are controlled as part of the path.
  */
 void coresight_disable_source(struct coresight_device *csdev, void *data)
 {
 	source_ops(csdev)->disable(csdev, data);
-	coresight_disable_helpers(csdev, NULL);
 }
 EXPORT_SYMBOL_GPL(coresight_disable_source);
 
@@ -486,9 +479,9 @@ int coresight_resume_source(struct coresight_device *csdev)
 EXPORT_SYMBOL_GPL(coresight_resume_source);
 
 /*
- * coresight_disable_path_from : Disable components in the given path beyond
- * @nd in the list. If @nd is NULL, all the components, except the SOURCE are
- * disabled.
+ * 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.
  */
 static void coresight_disable_path_from(struct coresight_path *path,
 					struct coresight_node *nd)
@@ -499,7 +492,7 @@ static void coresight_disable_path_from(struct coresight_path *path,
 	if (!nd)
 		nd = list_first_entry(&path->path_list, struct coresight_node, link);
 
-	list_for_each_entry_continue(nd, &path->path_list, link) {
+	list_for_each_entry_from(nd, &path->path_list, link) {
 		csdev = nd->csdev;
 		type = csdev->type;
 
@@ -519,12 +512,6 @@ static void coresight_disable_path_from(struct coresight_path *path,
 			coresight_disable_sink(csdev);
 			break;
 		case CORESIGHT_DEV_TYPE_SOURCE:
-			/*
-			 * We skip the first node in the path assuming that it
-			 * is the source. So we don't expect a source device in
-			 * the middle of a path.
-			 */
-			WARN_ON(1);
 			break;
 		case CORESIGHT_DEV_TYPE_LINK:
 			parent = list_prev_entry(nd, link)->csdev;
@@ -580,12 +567,16 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
 {
 	int ret = 0;
 	u32 type;
-	struct coresight_node *nd;
+	struct coresight_node *nd, *last;
 	struct coresight_device *csdev, *parent, *child;
 	struct coresight_device *source;
 
 	source = coresight_get_source(path);
-	list_for_each_entry_reverse(nd, &path->path_list, link) {
+
+	last = list_last_entry(&path->path_list, struct coresight_node, link);
+
+	nd = last;
+	list_for_each_entry_from_reverse(nd, &path->path_list, link) {
 		csdev = nd->csdev;
 		type = csdev->type;
 
@@ -639,6 +630,11 @@ int coresight_enable_path(struct coresight_path *path, enum cs_mode mode)
 err_disable_helpers:
 	coresight_disable_helpers(csdev, path);
 err_disable_path:
+	/* No device is actually enabled */
+	if (nd == last)
+		goto out;
+
+	nd = list_next_entry(nd, link);
 	coresight_disable_path_from(path, nd);
 	goto out;
 }

-- 
2.34.1