[03/21] coresight: associating path with session rather than tracer

diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
index 62fcd98cc7cf..7b193a34d709 100644
--- a/drivers/hwtracing/coresight/coresight-priv.h
+++ b/drivers/hwtracing/coresight/coresight-priv.h
@@ -52,6 +52,11 @@  static inline void CS_UNLOCK(void __iomem *addr)
 	} while (0);
 }
 
+void coresight_disable_path(struct list_head *path);
+int coresight_enable_path(struct list_head *path);
+struct list_head *coresight_build_path(struct coresight_device *csdev);
+void coresight_release_path(struct list_head *path);
+
 #ifdef CONFIG_CORESIGHT_SOURCE_ETM3X
 extern int etm_readl_cp14(u32 off, unsigned int *val);
 extern int etm_writel_cp14(u32 off, u32 val);
diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
index 7e6e9ff27dd1..f26589effb70 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -29,6 +29,22 @@ 
 
 static DEFINE_MUTEX(coresight_mutex);
 
+/**
+ * struct coresight_node - elements of a path, from source to sink
+ * @csdev:	Address of an element.
+ * @link:	hook to the list.
+ */
+struct coresight_node {
+	struct coresight_device *csdev;
+	struct list_head link;
+};
+
+/*
+ * When operating Coresight drivers from the sysFS interface, only a single
+ * path can exist from a tracer (associated to a CPU) to a sink.
+ */
+static DEFINE_PER_CPU(struct list_head *, sysfs_path);
+
 static int coresight_id_match(struct device *dev, void *data)
 {
 	int trace_id, i_trace_id;
@@ -68,15 +84,12 @@  static int coresight_source_is_unique(struct coresight_device *csdev)
 				 csdev, coresight_id_match);
 }
 
-static int coresight_find_link_inport(struct coresight_device *csdev)
+static int coresight_find_link_inport(struct coresight_device *csdev,
+				      struct coresight_device *parent)
 {
 	int i;
-	struct coresight_device *parent;
 	struct coresight_connection *conn;
 
-	parent = container_of(csdev->path_link.next,
-			      struct coresight_device, path_link);
-
 	for (i = 0; i < parent->nr_outport; i++) {
 		conn = &parent->conns[i];
 		if (conn->child_dev == csdev)
@@ -89,15 +102,12 @@  static int coresight_find_link_inport(struct coresight_device *csdev)
 	return 0;
 }
 
-static int coresight_find_link_outport(struct coresight_device *csdev)
+static int coresight_find_link_outport(struct coresight_device *csdev,
+				       struct coresight_device *child)
 {
 	int i;
-	struct coresight_device *child;
 	struct coresight_connection *conn;
 
-	child = container_of(csdev->path_link.prev,
-			     struct coresight_device, path_link);
-
 	for (i = 0; i < csdev->nr_outport; i++) {
 		conn = &csdev->conns[i];
 		if (conn->child_dev == child)
@@ -138,14 +148,19 @@  static void coresight_disable_sink(struct coresight_device *csdev)
 	}
 }
 
-static int coresight_enable_link(struct coresight_device *csdev)
+static int coresight_enable_link(struct coresight_device *csdev,
+				 struct coresight_device *parent,
+				 struct coresight_device *child)
 {
 	int ret;
 	int link_subtype;
 	int refport, inport, outport;
 
-	inport = coresight_find_link_inport(csdev);
-	outport = coresight_find_link_outport(csdev);
+	if (!parent || !child)
+		return -EINVAL;
+
+	inport = coresight_find_link_inport(csdev, parent);
+	outport = coresight_find_link_outport(csdev, child);
 	link_subtype = csdev->subtype.link_subtype;
 
 	if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG)
@@ -168,14 +183,19 @@  static int coresight_enable_link(struct coresight_device *csdev)
 	return 0;
 }
 
-static void coresight_disable_link(struct coresight_device *csdev)
+static void coresight_disable_link(struct coresight_device *csdev,
+				   struct coresight_device *parent,
+				   struct coresight_device *child)
 {
 	int i, nr_conns;
 	int link_subtype;
 	int refport, inport, outport;
 
-	inport = coresight_find_link_inport(csdev);
-	outport = coresight_find_link_outport(csdev);
+	if (!parent || !child)
+		return;
+
+	inport = coresight_find_link_inport(csdev, parent);
+	outport = coresight_find_link_outport(csdev, child);
 	link_subtype = csdev->subtype.link_subtype;
 
 	if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) {
@@ -235,109 +255,167 @@  static void coresight_disable_source(struct coresight_device *csdev)
 	}
 }
 
-static int coresight_enable_path(struct list_head *path)
+void coresight_disable_path(struct list_head *path)
 {
-	int ret = 0;
-	struct coresight_device *cd;
+	struct coresight_node *nd;
+	struct coresight_device *csdev, *parent, *child;
 
-	/*
-	 * At this point we have a full @path, from source to sink.  The
-	 * sink is the first entry and the source the last one.  Go through
-	 * all the components and enable them one by one.
-	 */
-	list_for_each_entry(cd, path, path_link) {
-		if (cd == list_first_entry(path, struct coresight_device,
-					   path_link)) {
-			ret = coresight_enable_sink(cd);
-		} else if (list_is_last(&cd->path_link, path)) {
-			/*
-			 * Don't enable the source just yet - this needs to
-			 * happen at the very end when all links and sink
-			 * along the path have been configured properly.
-			 */
-			;
-		} else {
-			ret = coresight_enable_link(cd);
+	list_for_each_entry(nd, path, link) {
+		csdev = nd->csdev;
+
+		switch (csdev->type) {
+		case CORESIGHT_DEV_TYPE_SINK:
+		case CORESIGHT_DEV_TYPE_LINKSINK:
+			coresight_disable_sink(csdev);
+			break;
+		case CORESIGHT_DEV_TYPE_SOURCE:
+			/* sources are disabled from either sysFS or Perf */
+			break;
+		case CORESIGHT_DEV_TYPE_LINK:
+			parent = list_prev_entry(nd, link)->csdev;
+			child = list_next_entry(nd, link)->csdev;
+			coresight_disable_link(csdev, parent, child);
+			break;
+		default:
+			break;
 		}
-		if (ret)
-			goto err;
 	}
+}
 
-	return 0;
-err:
-	list_for_each_entry_continue_reverse(cd, path, path_link) {
-		if (cd == list_first_entry(path, struct coresight_device,
-					   path_link)) {
-			coresight_disable_sink(cd);
-		} else if (list_is_last(&cd->path_link, path)) {
-			;
-		} else {
-			coresight_disable_link(cd);
+int coresight_enable_path(struct list_head *path)
+{
+
+	int ret = 0;
+	struct coresight_node *nd;
+	struct coresight_device *csdev, *parent, *child;
+
+	list_for_each_entry_reverse(nd, path, link) {
+		csdev = nd->csdev;
+
+		switch (csdev->type) {
+		case CORESIGHT_DEV_TYPE_SINK:
+		case CORESIGHT_DEV_TYPE_LINKSINK:
+			ret = coresight_enable_sink(csdev);
+			if (ret)
+				goto err;
+			break;
+		case CORESIGHT_DEV_TYPE_SOURCE:
+			/* sources are enabled from either sysFS or Perf */
+			break;
+		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);
+			if (ret)
+				goto err;
+			break;
+		default:
+			goto err;
 		}
 	}
 
+out:
 	return ret;
+err:
+	coresight_disable_path(path);
+	goto out;
 }
 
-static int coresight_disable_path(struct list_head *path)
+/**
+ * _coresight_build_path - recursively build a path from a @csdev to a sink.
+ * @csdev:	The device to start from.
+ * @path:	The list to add devices to.
+ *
+ * The tree of Coresight device is traversed until an activated sink is
+ * found.  From there the sink is added to the list along with all the
+ * devices that led to that point - the end result is a list from source
+ * to sink. In that list the source is the first device and the sink the
+ * last one.
+ */
+static int _coresight_build_path(struct coresight_device *csdev,
+				 struct list_head *path)
 {
-	struct coresight_device *cd;
+	int i;
+	bool found = false;
+	struct coresight_node *node;
+	struct coresight_connection *conn;
 
-	list_for_each_entry_reverse(cd, path, path_link) {
-		if (cd == list_first_entry(path, struct coresight_device,
-					   path_link)) {
-			coresight_disable_sink(cd);
-		} else if (list_is_last(&cd->path_link, path)) {
-			/*
-			 * The source has already been stopped, no need
-			 * to do it again here.
-			 */
-			;
-		} else {
-			coresight_disable_link(cd);
+	/* An activated sink has been found.  Enqueue the element */
+	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) && csdev->activated)
+		goto out;
+
+	/* Not a sink - recursively explore each port found on this element */
+	for (i = 0; i < csdev->nr_outport; i++) {
+		conn = &csdev->conns[i];
+		if (_coresight_build_path(conn->child_dev, path) == 0) {
+			found = true;
+			break;
 		}
 	}
 
+	if (!found)
+		return -ENODEV;
+
+out:
+	/*
+	 * A path from this element to a sink has been found.  The elements
+	 * leading to the sink are already enqueued, all that is left to do
+	 * is add a node for this element.
+	 */
+	node = kzalloc(sizeof(struct coresight_node), GFP_KERNEL);
+	if (!node)
+		return -ENOMEM;
+
+	node->csdev = csdev;
+	list_add(&node->link, path);
+
 	return 0;
 }
 
-static int coresight_build_paths(struct coresight_device *csdev,
-				 struct list_head *path,
-				 bool enable)
+struct list_head *coresight_build_path(struct coresight_device *csdev)
 {
-	int i, ret = -EINVAL;
-	struct coresight_connection *conn;
+	struct list_head *path;
 
-	list_add(&csdev->path_link, path);
+	path = kzalloc(sizeof(struct list_head), GFP_KERNEL);
+	if (!path)
+		return NULL;
 
-	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
-	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) &&
-	    csdev->activated) {
-		if (enable)
-			ret = coresight_enable_path(path);
-		else
-			ret = coresight_disable_path(path);
-	} else {
-		for (i = 0; i < csdev->nr_outport; i++) {
-			conn = &csdev->conns[i];
-			if (coresight_build_paths(conn->child_dev,
-						    path, enable) == 0)
-				ret = 0;
-		}
+	INIT_LIST_HEAD(path);
+
+	if (_coresight_build_path(csdev, path)) {
+		kfree(path);
+		path = NULL;
 	}
 
-	if (list_first_entry(path, struct coresight_device, path_link) != csdev)
-		dev_err(&csdev->dev, "wrong device in %s\n", __func__);
+	return path;
+}
 
-	list_del(&csdev->path_link);
+/**
+ * coresight_release_path - release a previously built path.
+ * @path:	the path to release.
+ *
+ * Go through all the elements of a path and 1) removed it from the list and
+ * 2) free the memory allocated for each node.
+ */
+void coresight_release_path(struct list_head *path)
+{
+	struct coresight_node *nd, *next;
 
-	return ret;
+	list_for_each_entry_safe(nd, next, path, link) {
+		list_del(&nd->link);
+		kfree(nd);
+	}
+
+	kfree(path);
+	path = NULL;
 }
 
 int coresight_enable(struct coresight_device *csdev)
 {
 	int ret = 0;
-	LIST_HEAD(path);
+	int cpu;
+	struct list_head *path;
 
 	mutex_lock(&coresight_mutex);
 	if (csdev->type != CORESIGHT_DEV_TYPE_SOURCE) {
@@ -348,22 +426,47 @@  int coresight_enable(struct coresight_device *csdev)
 	if (csdev->enable)
 		goto out;
 
-	if (coresight_build_paths(csdev, &path, true)) {
-		dev_err(&csdev->dev, "building path(s) failed\n");
+	path = coresight_build_path(csdev);
+	if (!path) {
+		pr_err("building path(s) failed\n");
 		goto out;
 	}
 
-	if (coresight_enable_source(csdev))
-		dev_err(&csdev->dev, "source enable failed\n");
+	ret = coresight_enable_path(path);
+	if (ret)
+		goto err_path;
+
+	ret = coresight_enable_source(csdev);
+	if (ret)
+		goto err_source;
+
+	/*
+	 * When working from sysFS it is important to keep track
+	 * of the paths that were created so that they can be
+	 * undone in 'coresight_disable()'.  Since there can only
+	 * be a single session per tracer (when working from sysFS)
+	 * a per-cpu variable will do just fine.
+	 */
+	cpu = source_ops(csdev)->cpu_id(csdev);
+	per_cpu(sysfs_path, cpu) = path;
+
 out:
 	mutex_unlock(&coresight_mutex);
 	return ret;
+
+err_source:
+	coresight_disable_path(path);
+
+err_path:
+	coresight_release_path(path);
+	goto out;
 }
 EXPORT_SYMBOL_GPL(coresight_enable);
 
 void coresight_disable(struct coresight_device *csdev)
 {
-	LIST_HEAD(path);
+	int cpu;
+	struct list_head *path;
 
 	mutex_lock(&coresight_mutex);
 	if (csdev->type != CORESIGHT_DEV_TYPE_SOURCE) {
@@ -373,9 +476,12 @@  void coresight_disable(struct coresight_device *csdev)
 	if (!csdev->enable)
 		goto out;
 
+	cpu = source_ops(csdev)->cpu_id(csdev);
+	path = per_cpu(sysfs_path, cpu);
 	coresight_disable_source(csdev);
-	if (coresight_build_paths(csdev, &path, false))
-		dev_err(&csdev->dev, "releasing path(s) failed\n");
+	coresight_disable_path(path);
+	coresight_release_path(path);
+	per_cpu(sysfs_path, cpu) = NULL;
 
 out:
 	mutex_unlock(&coresight_mutex);
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index bf62b265bf52..851ecb22397e 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -152,7 +152,6 @@  struct coresight_connection {
 		by @coresight_ops.
  * @dev:	The device entity associated to this component.
  * @refcnt:	keep track of what is in use.
- * @path_link:	link of current component into the path being enabled.
  * @orphan:	true if the component has connections that haven't been linked.
  * @enable:	'true' if component is currently part of an active path.
  * @activated:	'true' only if a _sink_ has been activated.  A sink can be
@@ -168,7 +167,6 @@  struct coresight_device {
 	const struct coresight_ops *ops;
 	struct device dev;
 	atomic_t *refcnt;
-	struct list_head path_link;
 	bool orphan;
 	bool enable;	/* true only if configured as part of a path */
 	bool activated;	/* true only if a sink is part of a path */