coresight: core: Allow the coresight core driver to be built as a module

Enhance coresight developer's efficiency to debug coresight drivers.
- Kconfig becomes a tristate, to allow =m
- append -core to source file name to allow module to
  be called coresight by the Makefile
- modules can have only one init/exit, so we add the etm_perf
  register/unregister function calls to the core init/exit
  functions.
- add a MODULE_DEVICE_TABLE for autoloading on boot

Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Tested-by: Mike Leach <mike.leach@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Kim Phillips <kim.phillips@arm.com>
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200928163513.70169-25-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1694 insertions, 0 deletions

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
new file mode 100644
index 000000000000..6994c1309b2b
--- /dev/null
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -0,0 +1,1694 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2012, The Linux Foundation. All rights reserved.
+ */
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/slab.h>
+#include <linux/stringhash.h>
+#include <linux/mutex.h>
+#include <linux/clk.h>
+#include <linux/coresight.h>
+#include <linux/of_platform.h>
+#include <linux/delay.h>
+#include <linux/pm_runtime.h>
+
+#include "coresight-etm-perf.h"
+#include "coresight-priv.h"
+
+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 *, tracer_path);
+
+/*
+ * As of this writing only a single STM can be found in CS topologies.  Since
+ * there is no way to know if we'll ever see more and what kind of
+ * configuration they will enact, for the time being only define a single path
+ * for STM.
+ */
+static struct list_head *stm_path;
+
+/*
+ * When losing synchronisation a new barrier packet needs to be inserted at the
+ * beginning of the data collected in a buffer.  That way the decoder knows that
+ * it needs to look for another sync sequence.
+ */
+const u32 coresight_barrier_pkt[4] = {0x7fffffff, 0x7fffffff, 0x7fffffff, 0x7fffffff};
+EXPORT_SYMBOL_GPL(coresight_barrier_pkt);
+
+static const struct cti_assoc_op *cti_assoc_ops;
+
+void coresight_set_cti_ops(const struct cti_assoc_op *cti_op)
+{
+	cti_assoc_ops = cti_op;
+}
+EXPORT_SYMBOL_GPL(coresight_set_cti_ops);
+
+void coresight_remove_cti_ops(void)
+{
+	cti_assoc_ops = NULL;
+}
+EXPORT_SYMBOL_GPL(coresight_remove_cti_ops);
+
+static int coresight_id_match(struct device *dev, void *data)
+{
+	int trace_id, i_trace_id;
+	struct coresight_device *csdev, *i_csdev;
+
+	csdev = data;
+	i_csdev = to_coresight_device(dev);
+
+	/*
+	 * No need to care about oneself and components that are not
+	 * sources or not enabled
+	 */
+	if (i_csdev == csdev || !i_csdev->enable ||
+	    i_csdev->type != CORESIGHT_DEV_TYPE_SOURCE)
+		return 0;
+
+	/* Get the source ID for both compoment */
+	trace_id = source_ops(csdev)->trace_id(csdev);
+	i_trace_id = source_ops(i_csdev)->trace_id(i_csdev);
+
+	/* All you need is one */
+	if (trace_id == i_trace_id)
+		return 1;
+
+	return 0;
+}
+
+static int coresight_source_is_unique(struct coresight_device *csdev)
+{
+	int trace_id = source_ops(csdev)->trace_id(csdev);
+
+	/* this shouldn't happen */
+	if (trace_id < 0)
+		return 0;
+
+	return !bus_for_each_dev(&coresight_bustype, NULL,
+				 csdev, coresight_id_match);
+}
+
+static int coresight_find_link_inport(struct coresight_device *csdev,
+				      struct coresight_device *parent)
+{
+	int i;
+	struct coresight_connection *conn;
+
+	for (i = 0; i < parent->pdata->nr_outport; i++) {
+		conn = &parent->pdata->conns[i];
+		if (conn->child_dev == csdev)
+			return conn->child_port;
+	}
+
+	dev_err(&csdev->dev, "couldn't find inport, parent: %s, child: %s\n",
+		dev_name(&parent->dev), dev_name(&csdev->dev));
+
+	return -ENODEV;
+}
+
+static int coresight_find_link_outport(struct coresight_device *csdev,
+				       struct coresight_device *child)
+{
+	int i;
+	struct coresight_connection *conn;
+
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		conn = &csdev->pdata->conns[i];
+		if (conn->child_dev == child)
+			return conn->outport;
+	}
+
+	dev_err(&csdev->dev, "couldn't find outport, parent: %s, child: %s\n",
+		dev_name(&csdev->dev), dev_name(&child->dev));
+
+	return -ENODEV;
+}
+
+static inline u32 coresight_read_claim_tags(void __iomem *base)
+{
+	return readl_relaxed(base + CORESIGHT_CLAIMCLR);
+}
+
+static inline bool coresight_is_claimed_self_hosted(void __iomem *base)
+{
+	return coresight_read_claim_tags(base) == CORESIGHT_CLAIM_SELF_HOSTED;
+}
+
+static inline bool coresight_is_claimed_any(void __iomem *base)
+{
+	return coresight_read_claim_tags(base) != 0;
+}
+
+static inline void coresight_set_claim_tags(void __iomem *base)
+{
+	writel_relaxed(CORESIGHT_CLAIM_SELF_HOSTED, base + CORESIGHT_CLAIMSET);
+	isb();
+}
+
+static inline void coresight_clear_claim_tags(void __iomem *base)
+{
+	writel_relaxed(CORESIGHT_CLAIM_SELF_HOSTED, base + CORESIGHT_CLAIMCLR);
+	isb();
+}
+
+/*
+ * coresight_claim_device_unlocked : Claim the device for self-hosted usage
+ * to prevent an external tool from touching this device. As per PSCI
+ * standards, section "Preserving the execution context" => "Debug and Trace
+ * save and Restore", DBGCLAIM[1] is reserved for Self-hosted debug/trace and
+ * DBGCLAIM[0] is reserved for external tools.
+ *
+ * Called with CS_UNLOCKed for the component.
+ * Returns : 0 on success
+ */
+int coresight_claim_device_unlocked(void __iomem *base)
+{
+	if (coresight_is_claimed_any(base))
+		return -EBUSY;
+
+	coresight_set_claim_tags(base);
+	if (coresight_is_claimed_self_hosted(base))
+		return 0;
+	/* There was a race setting the tags, clean up and fail */
+	coresight_clear_claim_tags(base);
+	return -EBUSY;
+}
+EXPORT_SYMBOL_GPL(coresight_claim_device_unlocked);
+
+int coresight_claim_device(void __iomem *base)
+{
+	int rc;
+
+	CS_UNLOCK(base);
+	rc = coresight_claim_device_unlocked(base);
+	CS_LOCK(base);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(coresight_claim_device);
+
+/*
+ * coresight_disclaim_device_unlocked : Clear the claim tags for the device.
+ * Called with CS_UNLOCKed for the component.
+ */
+void coresight_disclaim_device_unlocked(void __iomem *base)
+{
+
+	if (coresight_is_claimed_self_hosted(base))
+		coresight_clear_claim_tags(base);
+	else
+		/*
+		 * The external agent may have not honoured our claim
+		 * and has manipulated it. Or something else has seriously
+		 * gone wrong in our driver.
+		 */
+		WARN_ON_ONCE(1);
+}
+EXPORT_SYMBOL_GPL(coresight_disclaim_device_unlocked);
+
+void coresight_disclaim_device(void __iomem *base)
+{
+	CS_UNLOCK(base);
+	coresight_disclaim_device_unlocked(base);
+	CS_LOCK(base);
+}
+EXPORT_SYMBOL_GPL(coresight_disclaim_device);
+
+/* enable or disable an associated CTI device of the supplied CS device */
+static int
+coresight_control_assoc_ectdev(struct coresight_device *csdev, bool enable)
+{
+	int ect_ret = 0;
+	struct coresight_device *ect_csdev = csdev->ect_dev;
+	struct module *mod;
+
+	if (!ect_csdev)
+		return 0;
+	if ((!ect_ops(ect_csdev)->enable) || (!ect_ops(ect_csdev)->disable))
+		return 0;
+
+	mod = ect_csdev->dev.parent->driver->owner;
+	if (enable) {
+		if (try_module_get(mod)) {
+			ect_ret = ect_ops(ect_csdev)->enable(ect_csdev);
+			if (ect_ret) {
+				module_put(mod);
+			} else {
+				get_device(ect_csdev->dev.parent);
+				csdev->ect_enabled = true;
+			}
+		} else
+			ect_ret = -ENODEV;
+	} else {
+		if (csdev->ect_enabled) {
+			ect_ret = ect_ops(ect_csdev)->disable(ect_csdev);
+			put_device(ect_csdev->dev.parent);
+			module_put(mod);
+			csdev->ect_enabled = false;
+		}
+	}
+
+	/* output warning if ECT enable is preventing trace operation */
+	if (ect_ret)
+		dev_info(&csdev->dev, "Associated ECT device (%s) %s failed\n",
+			 dev_name(&ect_csdev->dev),
+			 enable ? "enable" : "disable");
+	return ect_ret;
+}
+
+/*
+ * Set the associated ect / cti device while holding the coresight_mutex
+ * to avoid a race with coresight_enable that may try to use this value.
+ */
+void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
+				      struct coresight_device *ect_csdev)
+{
+	mutex_lock(&coresight_mutex);
+	csdev->ect_dev = ect_csdev;
+	mutex_unlock(&coresight_mutex);
+}
+EXPORT_SYMBOL_GPL(coresight_set_assoc_ectdev_mutex);
+
+static int coresight_enable_sink(struct coresight_device *csdev,
+				 u32 mode, void *data)
+{
+	int ret;
+
+	/*
+	 * We need to make sure the "new" session is compatible with the
+	 * existing "mode" of operation.
+	 */
+	if (!sink_ops(csdev)->enable)
+		return -EINVAL;
+
+	ret = coresight_control_assoc_ectdev(csdev, true);
+	if (ret)
+		return ret;
+	ret = sink_ops(csdev)->enable(csdev, mode, data);
+	if (ret) {
+		coresight_control_assoc_ectdev(csdev, false);
+		return ret;
+	}
+	csdev->enable = true;
+
+	return 0;
+}
+
+static void coresight_disable_sink(struct coresight_device *csdev)
+{
+	int ret;
+
+	if (!sink_ops(csdev)->disable)
+		return;
+
+	ret = sink_ops(csdev)->disable(csdev);
+	if (ret)
+		return;
+	coresight_control_assoc_ectdev(csdev, false);
+	csdev->enable = false;
+}
+
+static int coresight_enable_link(struct coresight_device *csdev,
+				 struct coresight_device *parent,
+				 struct coresight_device *child)
+{
+	int ret = 0;
+	int link_subtype;
+	int inport, outport;
+
+	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 && inport < 0)
+		return inport;
+	if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT && outport < 0)
+		return outport;
+
+	if (link_ops(csdev)->enable) {
+		ret = coresight_control_assoc_ectdev(csdev, true);
+		if (!ret) {
+			ret = link_ops(csdev)->enable(csdev, inport, outport);
+			if (ret)
+				coresight_control_assoc_ectdev(csdev, false);
+		}
+	}
+
+	if (!ret)
+		csdev->enable = true;
+
+	return ret;
+}
+
+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 inport, outport;
+
+	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) {
+		nr_conns = csdev->pdata->nr_inport;
+	} else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT) {
+		nr_conns = csdev->pdata->nr_outport;
+	} else {
+		nr_conns = 1;
+	}
+
+	if (link_ops(csdev)->disable) {
+		link_ops(csdev)->disable(csdev, inport, outport);
+		coresight_control_assoc_ectdev(csdev, false);
+	}
+
+	for (i = 0; i < nr_conns; i++)
+		if (atomic_read(&csdev->refcnt[i]) != 0)
+			return;
+
+	csdev->enable = false;
+}
+
+static int coresight_enable_source(struct coresight_device *csdev, u32 mode)
+{
+	int ret;
+
+	if (!coresight_source_is_unique(csdev)) {
+		dev_warn(&csdev->dev, "traceID %d not unique\n",
+			 source_ops(csdev)->trace_id(csdev));
+		return -EINVAL;
+	}
+
+	if (!csdev->enable) {
+		if (source_ops(csdev)->enable) {
+			ret = coresight_control_assoc_ectdev(csdev, true);
+			if (ret)
+				return ret;
+			ret = source_ops(csdev)->enable(csdev, NULL, mode);
+			if (ret) {
+				coresight_control_assoc_ectdev(csdev, false);
+				return ret;
+			};
+		}
+		csdev->enable = true;
+	}
+
+	atomic_inc(csdev->refcnt);
+
+	return 0;
+}
+
+/**
+ *  coresight_disable_source - Drop the reference count by 1 and disable
+ *  the device if there are no users left.
+ *
+ *  @csdev - The coresight device to disable
+ *
+ *  Returns true if the device has been disabled.
+ */
+static bool coresight_disable_source(struct coresight_device *csdev)
+{
+	if (atomic_dec_return(csdev->refcnt) == 0) {
+		if (source_ops(csdev)->disable)
+			source_ops(csdev)->disable(csdev, NULL);
+		coresight_control_assoc_ectdev(csdev, false);
+		csdev->enable = false;
+	}
+	return !csdev->enable;
+}
+
+/*
+ * 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.
+ */
+static void coresight_disable_path_from(struct list_head *path,
+					struct coresight_node *nd)
+{
+	u32 type;
+	struct coresight_device *csdev, *parent, *child;
+
+	if (!nd)
+		nd = list_first_entry(path, struct coresight_node, link);
+
+	list_for_each_entry_continue(nd, path, link) {
+		csdev = nd->csdev;
+		type = csdev->type;
+
+		/*
+		 * ETF devices are tricky... They can be a link or a sink,
+		 * depending on how they are configured.  If an ETF has been
+		 * "activated" it will be configured as a sink, otherwise
+		 * go ahead with the link configuration.
+		 */
+		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
+			type = (csdev == coresight_get_sink(path)) ?
+						CORESIGHT_DEV_TYPE_SINK :
+						CORESIGHT_DEV_TYPE_LINK;
+
+		switch (type) {
+		case CORESIGHT_DEV_TYPE_SINK:
+			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;
+			child = list_next_entry(nd, link)->csdev;
+			coresight_disable_link(csdev, parent, child);
+			break;
+		default:
+			break;
+		}
+	}
+}
+
+void coresight_disable_path(struct list_head *path)
+{
+	coresight_disable_path_from(path, NULL);
+}
+EXPORT_SYMBOL_GPL(coresight_disable_path);
+
+int coresight_enable_path(struct list_head *path, u32 mode, void *sink_data)
+{
+
+	int ret = 0;
+	u32 type;
+	struct coresight_node *nd;
+	struct coresight_device *csdev, *parent, *child;
+
+	list_for_each_entry_reverse(nd, path, link) {
+		csdev = nd->csdev;
+		type = csdev->type;
+
+		/*
+		 * ETF devices are tricky... They can be a link or a sink,
+		 * depending on how they are configured.  If an ETF has been
+		 * "activated" it will be configured as a sink, otherwise
+		 * go ahead with the link configuration.
+		 */
+		if (type == CORESIGHT_DEV_TYPE_LINKSINK)
+			type = (csdev == coresight_get_sink(path)) ?
+						CORESIGHT_DEV_TYPE_SINK :
+						CORESIGHT_DEV_TYPE_LINK;
+
+		switch (type) {
+		case CORESIGHT_DEV_TYPE_SINK:
+			ret = coresight_enable_sink(csdev, mode, sink_data);
+			/*
+			 * Sink is the first component turned on. If we
+			 * failed to enable the sink, there are no components
+			 * that need disabling. Disabling the path here
+			 * would mean we could disrupt an existing session.
+			 */
+			if (ret)
+				goto out;
+			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_from(path, nd);
+	goto out;
+}
+
+struct coresight_device *coresight_get_sink(struct list_head *path)
+{
+	struct coresight_device *csdev;
+
+	if (!path)
+		return NULL;
+
+	csdev = list_last_entry(path, struct coresight_node, link)->csdev;
+	if (csdev->type != CORESIGHT_DEV_TYPE_SINK &&
+	    csdev->type != CORESIGHT_DEV_TYPE_LINKSINK)
+		return NULL;
+
+	return csdev;
+}
+
+static struct coresight_device *
+coresight_find_enabled_sink(struct coresight_device *csdev)
+{
+	int i;
+	struct coresight_device *sink;
+
+	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) &&
+	     csdev->activated)
+		return csdev;
+
+	/*
+	 * Recursively explore each port found on this element.
+	 */
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_device *child_dev;
+
+		child_dev = csdev->pdata->conns[i].child_dev;
+		if (child_dev)
+			sink = coresight_find_enabled_sink(child_dev);
+		if (sink)
+			return sink;
+	}
+
+	return NULL;
+}
+
+/**
+ * coresight_get_enabled_sink - returns the first enabled sink using
+ * connection based search starting from the source reference
+ *
+ * @source: Coresight source device reference
+ */
+struct coresight_device *
+coresight_get_enabled_sink(struct coresight_device *source)
+{
+	if (!source)
+		return NULL;
+
+	return coresight_find_enabled_sink(source);
+}
+
+static int coresight_sink_by_id(struct device *dev, const void *data)
+{
+	struct coresight_device *csdev = to_coresight_device(dev);
+	unsigned long hash;
+
+	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+
+		if (!csdev->ea)
+			return 0;
+		/*
+		 * See function etm_perf_add_symlink_sink() to know where
+		 * this comes from.
+		 */
+		hash = (unsigned long)csdev->ea->var;
+
+		if ((u32)hash == *(u32 *)data)
+			return 1;
+	}
+
+	return 0;
+}
+
+/**
+ * coresight_get_sink_by_id - returns the sink that matches the id
+ * @id: Id of the sink to match
+ *
+ * The name of a sink is unique, whether it is found on the AMBA bus or
+ * otherwise.  As such the hash of that name can easily be used to identify
+ * a sink.
+ */
+struct coresight_device *coresight_get_sink_by_id(u32 id)
+{
+	struct device *dev = NULL;
+
+	dev = bus_find_device(&coresight_bustype, NULL, &id,
+			      coresight_sink_by_id);
+
+	return dev ? to_coresight_device(dev) : NULL;
+}
+
+/**
+ * coresight_get_ref- Helper function to increase reference count to module
+ * and device.
+ * Return true in successful case and power up the device.
+ * Return false when failed to get reference of module.
+ */
+static inline bool coresight_get_ref(struct coresight_device *csdev)
+{
+	struct device *dev = csdev->dev.parent;
+
+	/* Make sure the driver can't be removed */
+	if (!try_module_get(dev->driver->owner))
+		return false;
+	/* Make sure the device can't go away */
+	get_device(dev);
+	pm_runtime_get_sync(dev);
+	return true;
+}
+
+/**
+ * coresight_put_ref- Helper function to decrease reference count to module
+ * and device. Power off the device.
+ */
+static inline void coresight_put_ref(struct coresight_device *csdev)
+{
+	struct device *dev = csdev->dev.parent;
+
+	pm_runtime_put(dev);
+	put_device(dev);
+	module_put(dev->driver->owner);
+}
+
+/*
+ * coresight_grab_device - Power up this device and any of the helper
+ * devices connected to it for trace operation. Since the helper devices
+ * don't appear on the trace path, they should be handled along with the
+ * the master device.
+ */
+static int coresight_grab_device(struct coresight_device *csdev)
+{
+	int i;
+
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_device *child;
+
+		child  = csdev->pdata->conns[i].child_dev;
+		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
+			if (!coresight_get_ref(child))
+				goto err;
+	}
+	if (coresight_get_ref(csdev))
+		return 0;
+err:
+	for (i--; i >= 0; i--) {
+		struct coresight_device *child;
+
+		child  = csdev->pdata->conns[i].child_dev;
+		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
+			coresight_put_ref(child);
+	}
+	return -ENODEV;
+}
+
+/*
+ * coresight_drop_device - Release this device and any of the helper
+ * devices connected to it.
+ */
+static void coresight_drop_device(struct coresight_device *csdev)
+{
+	int i;
+
+	coresight_put_ref(csdev);
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_device *child;
+
+		child  = csdev->pdata->conns[i].child_dev;
+		if (child && child->type == CORESIGHT_DEV_TYPE_HELPER)
+			coresight_put_ref(child);
+	}
+}
+
+/**
+ * _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 coresight_device *sink,
+				 struct list_head *path)
+{
+	int i, ret;
+	bool found = false;
+	struct coresight_node *node;
+
+	/* An activated sink has been found.  Enqueue the element */
+	if (csdev == sink)
+		goto out;
+
+	/* Not a sink - recursively explore each port found on this element */
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_device *child_dev;
+
+		child_dev = csdev->pdata->conns[i].child_dev;
+		if (child_dev &&
+		    _coresight_build_path(child_dev, sink, 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 tell the PM runtime core we need this element and add a node
+	 * for it.
+	 */
+	ret = coresight_grab_device(csdev);
+	if (ret)
+		return ret;
+
+	node = kzalloc(sizeof(struct coresight_node), GFP_KERNEL);
+	if (!node)
+		return -ENOMEM;
+
+	node->csdev = csdev;
+	list_add(&node->link, path);
+
+	return 0;
+}
+
+struct list_head *coresight_build_path(struct coresight_device *source,
+				       struct coresight_device *sink)
+{
+	struct list_head *path;
+	int rc;
+
+	if (!sink)
+		return ERR_PTR(-EINVAL);
+
+	path = kzalloc(sizeof(struct list_head), GFP_KERNEL);
+	if (!path)
+		return ERR_PTR(-ENOMEM);
+
+	INIT_LIST_HEAD(path);
+
+	rc = _coresight_build_path(source, sink, path);
+	if (rc) {
+		kfree(path);
+		return ERR_PTR(rc);
+	}
+
+	return path;
+}
+
+/**
+ * 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_device *csdev;
+	struct coresight_node *nd, *next;
+
+	list_for_each_entry_safe(nd, next, path, link) {
+		csdev = nd->csdev;
+
+		coresight_drop_device(csdev);
+		list_del(&nd->link);
+		kfree(nd);
+	}
+
+	kfree(path);
+	path = NULL;
+}
+
+/* return true if the device is a suitable type for a default sink */
+static inline bool coresight_is_def_sink_type(struct coresight_device *csdev)
+{
+	/* sink & correct subtype */
+	if (((csdev->type == CORESIGHT_DEV_TYPE_SINK) ||
+	     (csdev->type == CORESIGHT_DEV_TYPE_LINKSINK)) &&
+	    (csdev->subtype.sink_subtype >= CORESIGHT_DEV_SUBTYPE_SINK_BUFFER))
+		return true;
+	return false;
+}
+
+/**
+ * coresight_select_best_sink - return the best sink for use as default from
+ * the two provided.
+ *
+ * @sink:	current best sink.
+ * @depth:      search depth where current sink was found.
+ * @new_sink:	new sink for comparison with current sink.
+ * @new_depth:  search depth where new sink was found.
+ *
+ * Sinks prioritised according to coresight_dev_subtype_sink, with only
+ * subtypes CORESIGHT_DEV_SUBTYPE_SINK_BUFFER or higher being used.
+ *
+ * Where two sinks of equal priority are found, the sink closest to the
+ * source is used (smallest search depth).
+ *
+ * return @new_sink & update @depth if better than @sink, else return @sink.
+ */
+static struct coresight_device *
+coresight_select_best_sink(struct coresight_device *sink, int *depth,
+			   struct coresight_device *new_sink, int new_depth)
+{
+	bool update = false;
+
+	if (!sink) {
+		/* first found at this level */
+		update = true;
+	} else if (new_sink->subtype.sink_subtype >
+		   sink->subtype.sink_subtype) {
+		/* found better sink */
+		update = true;
+	} else if ((new_sink->subtype.sink_subtype ==
+		    sink->subtype.sink_subtype) &&
+		   (*depth > new_depth)) {
+		/* found same but closer sink */
+		update = true;
+	}
+
+	if (update)
+		*depth = new_depth;
+	return update ? new_sink : sink;
+}
+
+/**
+ * coresight_find_sink - recursive function to walk trace connections from
+ * source to find a suitable default sink.
+ *
+ * @csdev: source / current device to check.
+ * @depth: [in] search depth of calling dev, [out] depth of found sink.
+ *
+ * This will walk the connection path from a source (ETM) till a suitable
+ * sink is encountered and return that sink to the original caller.
+ *
+ * If current device is a plain sink return that & depth, otherwise recursively
+ * call child connections looking for a sink. Select best possible using
+ * coresight_select_best_sink.
+ *
+ * return best sink found, or NULL if not found at this node or child nodes.
+ */
+static struct coresight_device *
+coresight_find_sink(struct coresight_device *csdev, int *depth)
+{
+	int i, curr_depth = *depth + 1, found_depth = 0;
+	struct coresight_device *found_sink = NULL;
+
+	if (coresight_is_def_sink_type(csdev)) {
+		found_depth = curr_depth;
+		found_sink = csdev;
+		if (csdev->type == CORESIGHT_DEV_TYPE_SINK)
+			goto return_def_sink;
+		/* look past LINKSINK for something better */
+	}
+
+	/*
+	 * Not a sink we want - or possible child sink may be better.
+	 * recursively explore each port found on this element.
+	 */
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_device *child_dev, *sink = NULL;
+		int child_depth = curr_depth;
+
+		child_dev = csdev->pdata->conns[i].child_dev;
+		if (child_dev)
+			sink = coresight_find_sink(child_dev, &child_depth);
+
+		if (sink)
+			found_sink = coresight_select_best_sink(found_sink,
+								&found_depth,
+								sink,
+								child_depth);
+	}
+
+return_def_sink:
+	/* return found sink and depth */
+	if (found_sink)
+		*depth = found_depth;
+	return found_sink;
+}
+
+/**
+ * coresight_find_default_sink: Find a sink suitable for use as a
+ * default sink.
+ *
+ * @csdev: starting source to find a connected sink.
+ *
+ * Walks connections graph looking for a suitable sink to enable for the
+ * supplied source. Uses CoreSight device subtypes and distance from source
+ * to select the best sink.
+ *
+ * If a sink is found, then the default sink for this device is set and
+ * will be automatically used in future.
+ *
+ * Used in cases where the CoreSight user (perf / sysfs) has not selected a
+ * sink.
+ */
+struct coresight_device *
+coresight_find_default_sink(struct coresight_device *csdev)
+{
+	int depth = 0;
+
+	/* look for a default sink if we have not found for this device */
+	if (!csdev->def_sink)
+		csdev->def_sink = coresight_find_sink(csdev, &depth);
+	return csdev->def_sink;
+}
+
+static int coresight_remove_sink_ref(struct device *dev, void *data)
+{
+	struct coresight_device *sink = data;
+	struct coresight_device *source = to_coresight_device(dev);
+
+	if (source->def_sink == sink)
+		source->def_sink = NULL;
+	return 0;
+}
+
+/**
+ * coresight_clear_default_sink: Remove all default sink references to the
+ * supplied sink.
+ *
+ * If supplied device is a sink, then check all the bus devices and clear
+ * out all the references to this sink from the coresight_device def_sink
+ * parameter.
+ *
+ * @csdev: coresight sink - remove references to this from all sources.
+ */
+static void coresight_clear_default_sink(struct coresight_device *csdev)
+{
+	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK) ||
+	    (csdev->type == CORESIGHT_DEV_TYPE_LINKSINK)) {
+		bus_for_each_dev(&coresight_bustype, NULL, csdev,
+				 coresight_remove_sink_ref);
+	}
+}
+
+/** coresight_validate_source - make sure a source has the right credentials
+ *  @csdev:	the device structure for a source.
+ *  @function:	the function this was called from.
+ *
+ * Assumes the coresight_mutex is held.
+ */
+static int coresight_validate_source(struct coresight_device *csdev,
+				     const char *function)
+{
+	u32 type, subtype;
+
+	type = csdev->type;
+	subtype = csdev->subtype.source_subtype;
+
+	if (type != CORESIGHT_DEV_TYPE_SOURCE) {
+		dev_err(&csdev->dev, "wrong device type in %s\n", function);
+		return -EINVAL;
+	}
+
+	if (subtype != CORESIGHT_DEV_SUBTYPE_SOURCE_PROC &&
+	    subtype != CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE) {
+		dev_err(&csdev->dev, "wrong device subtype in %s\n", function);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+int coresight_enable(struct coresight_device *csdev)
+{
+	int cpu, ret = 0;
+	struct coresight_device *sink;
+	struct list_head *path;
+	enum coresight_dev_subtype_source subtype;
+
+	subtype = csdev->subtype.source_subtype;
+
+	mutex_lock(&coresight_mutex);
+
+	ret = coresight_validate_source(csdev, __func__);
+	if (ret)
+		goto out;
+
+	if (csdev->enable) {
+		/*
+		 * There could be multiple applications driving the software
+		 * source. So keep the refcount for each such user when the
+		 * source is already enabled.
+		 */
+		if (subtype == CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE)
+			atomic_inc(csdev->refcnt);
+		goto out;
+	}
+
+	sink = coresight_get_enabled_sink(csdev);
+	if (!sink) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	path = coresight_build_path(csdev, sink);
+	if (IS_ERR(path)) {
+		pr_err("building path(s) failed\n");
+		ret = PTR_ERR(path);
+		goto out;
+	}
+
+	ret = coresight_enable_path(path, CS_MODE_SYSFS, NULL);
+	if (ret)
+		goto err_path;
+
+	ret = coresight_enable_source(csdev, CS_MODE_SYSFS);
+	if (ret)
+		goto err_source;
+
+	switch (subtype) {
+	case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
+		/*
+		 * 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(tracer_path, cpu) = path;
+		break;
+	case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
+		stm_path = path;
+		break;
+	default:
+		/* We can't be here */
+		break;
+	}
+
+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)
+{
+	int cpu, ret;
+	struct list_head *path = NULL;
+
+	mutex_lock(&coresight_mutex);
+
+	ret = coresight_validate_source(csdev, __func__);
+	if (ret)
+		goto out;
+
+	if (!csdev->enable || !coresight_disable_source(csdev))
+		goto out;
+
+	switch (csdev->subtype.source_subtype) {
+	case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
+		cpu = source_ops(csdev)->cpu_id(csdev);
+		path = per_cpu(tracer_path, cpu);
+		per_cpu(tracer_path, cpu) = NULL;
+		break;
+	case CORESIGHT_DEV_SUBTYPE_SOURCE_SOFTWARE:
+		path = stm_path;
+		stm_path = NULL;
+		break;
+	default:
+		/* We can't be here */
+		break;
+	}
+
+	coresight_disable_path(path);
+	coresight_release_path(path);
+
+out:
+	mutex_unlock(&coresight_mutex);
+}
+EXPORT_SYMBOL_GPL(coresight_disable);
+
+static ssize_t enable_sink_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct coresight_device *csdev = to_coresight_device(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->activated);
+}
+
+static ssize_t enable_sink_store(struct device *dev,
+				 struct device_attribute *attr,
+				 const char *buf, size_t size)
+{
+	int ret;
+	unsigned long val;
+	struct coresight_device *csdev = to_coresight_device(dev);
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	if (val)
+		csdev->activated = true;
+	else
+		csdev->activated = false;
+
+	return size;
+
+}
+static DEVICE_ATTR_RW(enable_sink);
+
+static ssize_t enable_source_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct coresight_device *csdev = to_coresight_device(dev);
+
+	return scnprintf(buf, PAGE_SIZE, "%u\n", csdev->enable);
+}
+
+static ssize_t enable_source_store(struct device *dev,
+				   struct device_attribute *attr,
+				   const char *buf, size_t size)
+{
+	int ret = 0;
+	unsigned long val;
+	struct coresight_device *csdev = to_coresight_device(dev);
+
+	ret = kstrtoul(buf, 10, &val);
+	if (ret)
+		return ret;
+
+	if (val) {
+		ret = coresight_enable(csdev);
+		if (ret)
+			return ret;
+	} else {
+		coresight_disable(csdev);
+	}
+
+	return size;
+}
+static DEVICE_ATTR_RW(enable_source);
+
+static struct attribute *coresight_sink_attrs[] = {
+	&dev_attr_enable_sink.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(coresight_sink);
+
+static struct attribute *coresight_source_attrs[] = {
+	&dev_attr_enable_source.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(coresight_source);
+
+static struct device_type coresight_dev_type[] = {
+	{
+		.name = "none",
+	},
+	{
+		.name = "sink",
+		.groups = coresight_sink_groups,
+	},
+	{
+		.name = "link",
+	},
+	{
+		.name = "linksink",
+		.groups = coresight_sink_groups,
+	},
+	{
+		.name = "source",
+		.groups = coresight_source_groups,
+	},
+	{
+		.name = "helper",
+	},
+	{
+		.name = "ect",
+	},
+};
+
+static void coresight_device_release(struct device *dev)
+{
+	struct coresight_device *csdev = to_coresight_device(dev);
+
+	fwnode_handle_put(csdev->dev.fwnode);
+	kfree(csdev->refcnt);
+	kfree(csdev);
+}
+
+static int coresight_orphan_match(struct device *dev, void *data)
+{
+	int i, ret = 0;
+	bool still_orphan = false;
+	struct coresight_device *csdev, *i_csdev;
+	struct coresight_connection *conn;
+
+	csdev = data;
+	i_csdev = to_coresight_device(dev);
+
+	/* No need to check oneself */
+	if (csdev == i_csdev)
+		return 0;
+
+	/* Move on to another component if no connection is orphan */
+	if (!i_csdev->orphan)
+		return 0;
+	/*
+	 * Circle throuch all the connection of that component.  If we find
+	 * an orphan connection whose name matches @csdev, link it.
+	 */
+	for (i = 0; i < i_csdev->pdata->nr_outport; i++) {
+		conn = &i_csdev->pdata->conns[i];
+
+		/* Skip the port if FW doesn't describe it */
+		if (!conn->child_fwnode)
+			continue;
+		/* We have found at least one orphan connection */
+		if (conn->child_dev == NULL) {
+			/* Does it match this newly added device? */
+			if (conn->child_fwnode == csdev->dev.fwnode) {
+				ret = coresight_make_links(i_csdev,
+							   conn, csdev);
+				if (ret)
+					return ret;
+			} else {
+				/* This component still has an orphan */
+				still_orphan = true;
+			}
+		}
+	}
+
+	i_csdev->orphan = still_orphan;
+
+	/*
+	 * Returning '0' in case we didn't encounter any error,
+	 * ensures that all known component on the bus will be checked.
+	 */
+	return 0;
+}
+
+static int coresight_fixup_orphan_conns(struct coresight_device *csdev)
+{
+	return bus_for_each_dev(&coresight_bustype, NULL,
+			 csdev, coresight_orphan_match);
+}
+
+
+static int coresight_fixup_device_conns(struct coresight_device *csdev)
+{
+	int i, ret = 0;
+
+	for (i = 0; i < csdev->pdata->nr_outport; i++) {
+		struct coresight_connection *conn = &csdev->pdata->conns[i];
+
+		if (!conn->child_fwnode)
+			continue;
+		conn->child_dev =
+			coresight_find_csdev_by_fwnode(conn->child_fwnode);
+		if (conn->child_dev) {
+			ret = coresight_make_links(csdev, conn,
+						   conn->child_dev);
+			if (ret)
+				break;
+		} else {
+			csdev->orphan = true;
+		}
+	}
+
+	return 0;
+}
+
+static int coresight_remove_match(struct device *dev, void *data)
+{
+	int i;
+	struct coresight_device *csdev, *iterator;
+	struct coresight_connection *conn;
+
+	csdev = data;
+	iterator = to_coresight_device(dev);
+
+	/* No need to check oneself */
+	if (csdev == iterator)
+		return 0;
+
+	/*
+	 * Circle throuch all the connection of that component.  If we find
+	 * a connection whose name matches @csdev, remove it.
+	 */
+	for (i = 0; i < iterator->pdata->nr_outport; i++) {
+		conn = &iterator->pdata->conns[i];
+
+		if (conn->child_dev == NULL || conn->child_fwnode == NULL)
+			continue;
+
+		if (csdev->dev.fwnode == conn->child_fwnode) {
+			iterator->orphan = true;
+			coresight_remove_links(iterator, conn);
+			/*
+			 * Drop the reference to the handle for the remote
+			 * device acquired in parsing the connections from
+			 * platform data.
+			 */
+			fwnode_handle_put(conn->child_fwnode);
+			/* No need to continue */
+			break;
+		}
+	}
+
+	/*
+	 * Returning '0' ensures that all known component on the
+	 * bus will be checked.
+	 */
+	return 0;
+}
+
+/*
+ * coresight_remove_conns - Remove references to this given devices
+ * from the connections of other devices.
+ */
+static void coresight_remove_conns(struct coresight_device *csdev)
+{
+	/*
+	 * Another device will point to this device only if there is
+	 * an output port connected to this one. i.e, if the device
+	 * doesn't have at least one input port, there is no point
+	 * in searching all the devices.
+	 */
+	if (csdev->pdata->nr_inport)
+		bus_for_each_dev(&coresight_bustype, NULL,
+				 csdev, coresight_remove_match);
+}
+
+/**
+ * coresight_timeout - loop until a bit has changed to a specific state.
+ * @addr: base address of the area of interest.
+ * @offset: address of a register, starting from @addr.
+ * @position: the position of the bit of interest.
+ * @value: the value the bit should have.
+ *
+ * Return: 0 as soon as the bit has taken the desired state or -EAGAIN if
+ * TIMEOUT_US has elapsed, which ever happens first.
+ */
+
+int coresight_timeout(void __iomem *addr, u32 offset, int position, int value)
+{
+	int i;
+	u32 val;
+
+	for (i = TIMEOUT_US; i > 0; i--) {
+		val = __raw_readl(addr + offset);
+		/* waiting on the bit to go from 0 to 1 */
+		if (value) {
+			if (val & BIT(position))
+				return 0;
+		/* waiting on the bit to go from 1 to 0 */
+		} else {
+			if (!(val & BIT(position)))
+				return 0;
+		}
+
+		/*
+		 * Delay is arbitrary - the specification doesn't say how long
+		 * we are expected to wait.  Extra check required to make sure
+		 * we don't wait needlessly on the last iteration.
+		 */
+		if (i - 1)
+			udelay(1);
+	}
+
+	return -EAGAIN;
+}
+EXPORT_SYMBOL_GPL(coresight_timeout);
+
+/*
+ * coresight_release_platform_data: Release references to the devices connected
+ * to the output port of this device.
+ */
+void coresight_release_platform_data(struct coresight_device *csdev,
+				     struct coresight_platform_data *pdata)
+{
+	int i;
+	struct coresight_connection *conns = pdata->conns;
+
+	for (i = 0; i < pdata->nr_outport; i++) {
+		/* If we have made the links, remove them now */
+		if (csdev && conns[i].child_dev)
+			coresight_remove_links(csdev, &conns[i]);
+		/*
+		 * Drop the refcount and clear the handle as this device
+		 * is going away
+		 */
+		if (conns[i].child_fwnode) {
+			fwnode_handle_put(conns[i].child_fwnode);
+			pdata->conns[i].child_fwnode = NULL;
+		}
+	}
+	if (csdev)
+		coresight_remove_conns_sysfs_group(csdev);
+}
+
+struct coresight_device *coresight_register(struct coresight_desc *desc)
+{
+	int ret;
+	int link_subtype;
+	int nr_refcnts = 1;
+	atomic_t *refcnts = NULL;
+	struct coresight_device *csdev;
+
+	csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
+	if (!csdev) {
+		ret = -ENOMEM;
+		goto err_out;
+	}
+
+	if (desc->type == CORESIGHT_DEV_TYPE_LINK ||
+	    desc->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+		link_subtype = desc->subtype.link_subtype;
+
+		if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG)
+			nr_refcnts = desc->pdata->nr_inport;
+		else if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_SPLIT)
+			nr_refcnts = desc->pdata->nr_outport;
+	}
+
+	refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
+	if (!refcnts) {
+		ret = -ENOMEM;
+		goto err_free_csdev;
+	}
+
+	csdev->refcnt = refcnts;
+
+	csdev->pdata = desc->pdata;
+
+	csdev->type = desc->type;
+	csdev->subtype = desc->subtype;
+	csdev->ops = desc->ops;
+	csdev->orphan = false;
+
+	csdev->dev.type = &coresight_dev_type[desc->type];
+	csdev->dev.groups = desc->groups;
+	csdev->dev.parent = desc->dev;
+	csdev->dev.release = coresight_device_release;
+	csdev->dev.bus = &coresight_bustype;
+	/*
+	 * Hold the reference to our parent device. This will be
+	 * dropped only in coresight_device_release().
+	 */
+	csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
+	dev_set_name(&csdev->dev, "%s", desc->name);
+
+	ret = device_register(&csdev->dev);
+	if (ret) {
+		put_device(&csdev->dev);
+		/*
+		 * All resources are free'd explicitly via
+		 * coresight_device_release(), triggered from put_device().
+		 */
+		goto err_out;
+	}
+
+	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+		ret = etm_perf_add_symlink_sink(csdev);
+
+		if (ret) {
+			device_unregister(&csdev->dev);
+			/*
+			 * As with the above, all resources are free'd
+			 * explicitly via coresight_device_release() triggered
+			 * from put_device(), which is in turn called from
+			 * function device_unregister().
+			 */
+			goto err_out;
+		}
+	}
+
+	mutex_lock(&coresight_mutex);
+
+	ret = coresight_create_conns_sysfs_group(csdev);
+	if (!ret)
+		ret = coresight_fixup_device_conns(csdev);
+	if (!ret)
+		ret = coresight_fixup_orphan_conns(csdev);
+	if (!ret && cti_assoc_ops && cti_assoc_ops->add)
+		cti_assoc_ops->add(csdev);
+
+	mutex_unlock(&coresight_mutex);
+	if (ret) {
+		coresight_unregister(csdev);
+		return ERR_PTR(ret);
+	}
+
+	return csdev;
+
+err_free_csdev:
+	kfree(csdev);
+err_out:
+	/* Cleanup the connection information */
+	coresight_release_platform_data(NULL, desc->pdata);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(coresight_register);
+
+void coresight_unregister(struct coresight_device *csdev)
+{
+	etm_perf_del_symlink_sink(csdev);
+	/* Remove references of that device in the topology */
+	if (cti_assoc_ops && cti_assoc_ops->remove)
+		cti_assoc_ops->remove(csdev);
+	coresight_remove_conns(csdev);
+	coresight_clear_default_sink(csdev);
+	coresight_release_platform_data(csdev, csdev->pdata);
+	device_unregister(&csdev->dev);
+}
+EXPORT_SYMBOL_GPL(coresight_unregister);
+
+
+/*
+ * coresight_search_device_idx - Search the fwnode handle of a device
+ * in the given dev_idx list. Must be called with the coresight_mutex held.
+ *
+ * Returns the index of the entry, when found. Otherwise, -ENOENT.
+ */
+static inline int coresight_search_device_idx(struct coresight_dev_list *dict,
+					      struct fwnode_handle *fwnode)
+{
+	int i;
+
+	for (i = 0; i < dict->nr_idx; i++)
+		if (dict->fwnode_list[i] == fwnode)
+			return i;
+	return -ENOENT;
+}
+
+bool coresight_loses_context_with_cpu(struct device *dev)
+{
+	return fwnode_property_present(dev_fwnode(dev),
+				       "arm,coresight-loses-context-with-cpu");
+}
+EXPORT_SYMBOL_GPL(coresight_loses_context_with_cpu);
+
+/*
+ * coresight_alloc_device_name - Get an index for a given device in the
+ * device index list specific to a driver. An index is allocated for a
+ * device and is tracked with the fwnode_handle to prevent allocating
+ * duplicate indices for the same device (e.g, if we defer probing of
+ * a device due to dependencies), in case the index is requested again.
+ */
+char *coresight_alloc_device_name(struct coresight_dev_list *dict,
+				  struct device *dev)
+{
+	int idx;
+	char *name = NULL;
+	struct fwnode_handle **list;
+
+	mutex_lock(&coresight_mutex);
+
+	idx = coresight_search_device_idx(dict, dev_fwnode(dev));
+	if (idx < 0) {
+		/* Make space for the new entry */
+		idx = dict->nr_idx;
+		list = krealloc(dict->fwnode_list,
+				(idx + 1) * sizeof(*dict->fwnode_list),
+				GFP_KERNEL);
+		if (ZERO_OR_NULL_PTR(list)) {
+			idx = -ENOMEM;
+			goto done;
+		}
+
+		list[idx] = dev_fwnode(dev);
+		dict->fwnode_list = list;
+		dict->nr_idx = idx + 1;
+	}
+
+	name = devm_kasprintf(dev, GFP_KERNEL, "%s%d", dict->pfx, idx);
+done:
+	mutex_unlock(&coresight_mutex);
+	return name;
+}
+EXPORT_SYMBOL_GPL(coresight_alloc_device_name);
+
+struct bus_type coresight_bustype = {
+	.name	= "coresight",
+};
+
+static int __init coresight_init(void)
+{
+	int ret;
+
+	ret = bus_register(&coresight_bustype);
+	if (ret)
+		return ret;
+
+	ret = etm_perf_init();
+	if (ret)
+		bus_unregister(&coresight_bustype);
+
+	return ret;
+}
+
+static void __exit coresight_exit(void)
+{
+	etm_perf_exit();
+	bus_unregister(&coresight_bustype);
+}
+
+module_init(coresight_init);
+module_exit(coresight_exit);
+
+MODULE_AUTHOR("Pratik Patel <pratikp@codeaurora.org>");
+MODULE_AUTHOR("Mathieu Poirier <mathieu.poirier@linaro.org>");
+MODULE_DESCRIPTION("Arm CoreSight tracer driver");