Merge tag 'for-v4.6-rc/omap-fixes-a' of git://git.kernel.org/pub/scm/linux/kernel/git/pjw/omap-pending into omap-for-v4.6/fixes

ARM: OMAP2+: first hwmod fix for v4.6-rc

Fix a longstanding bug in the hwmod code that could cause
hardware SYSCONFIG register values to not match the kernel's
idea of what they should be, and that could result in lower
performance during IP block idle entry.

Basic build, boot, and PM test logs are available here:

http://www.pwsan.com/omap/testlogs/omap-hwmod-fixes-a-for-v4.6-rc/20160326231727/

7 files changed, 367 insertions, 54 deletions

diff --git a/drivers/hwtracing/stm/Kconfig b/drivers/hwtracing/stm/Kconfig
index 83e9f591a54b..847a39b35307 100644
--- a/drivers/hwtracing/stm/Kconfig
+++ b/drivers/hwtracing/stm/Kconfig
@@ -1,6 +1,7 @@
 config STM
 	tristate "System Trace Module devices"
 	select CONFIGFS_FS
+	select SRCU
 	help
 	  A System Trace Module (STM) is a device exporting data in System
 	  Trace Protocol (STP) format as defined by MIPI STP standards.
@@ -8,6 +9,8 @@ config STM
 
 	  Say Y here to enable System Trace Module device support.
 
+if STM
+
 config STM_DUMMY
 	tristate "Dummy STM driver"
 	help
@@ -24,3 +27,16 @@ config STM_SOURCE_CONSOLE
 
 	  If you want to send kernel console messages over STM devices,
 	  say Y.
+
+config STM_SOURCE_HEARTBEAT
+	tristate "Heartbeat over STM devices"
+	help
+	  This is a kernel space trace source that sends periodic
+	  heartbeat messages to trace hosts over STM devices. It is
+	  also useful for testing stm class drivers and the stm class
+	  framework itself.
+
+	  If you want to send heartbeat messages over STM devices,
+	  say Y.
+
+endif
diff --git a/drivers/hwtracing/stm/Makefile b/drivers/hwtracing/stm/Makefile
index f9312c38dd7a..a9ce3d487e57 100644
--- a/drivers/hwtracing/stm/Makefile
+++ b/drivers/hwtracing/stm/Makefile
@@ -5,5 +5,7 @@ stm_core-y		:= core.o policy.o
 obj-$(CONFIG_STM_DUMMY)	+= dummy_stm.o
 
 obj-$(CONFIG_STM_SOURCE_CONSOLE)	+= stm_console.o
+obj-$(CONFIG_STM_SOURCE_HEARTBEAT)	+= stm_heartbeat.o
 
 stm_console-y		:= console.o
+stm_heartbeat-y		:= heartbeat.o
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c
index b6445d9e5453..de80d45d8df9 100644
--- a/drivers/hwtracing/stm/core.c
+++ b/drivers/hwtracing/stm/core.c
@@ -113,6 +113,7 @@ struct stm_device *stm_find_device(const char *buf)
 
 	stm = to_stm_device(dev);
 	if (!try_module_get(stm->owner)) {
+		/* matches class_find_device() above */
 		put_device(dev);
 		return NULL;
 	}
@@ -125,7 +126,7 @@ struct stm_device *stm_find_device(const char *buf)
  * @stm:	stm device, previously acquired by stm_find_device()
  *
  * This drops the module reference and device reference taken by
- * stm_find_device().
+ * stm_find_device() or stm_char_open().
  */
 void stm_put_device(struct stm_device *stm)
 {
@@ -185,6 +186,9 @@ static void stm_output_claim(struct stm_device *stm, struct stm_output *output)
 {
 	struct stp_master *master = stm_master(stm, output->master);
 
+	lockdep_assert_held(&stm->mc_lock);
+	lockdep_assert_held(&output->lock);
+
 	if (WARN_ON_ONCE(master->nr_free < output->nr_chans))
 		return;
 
@@ -199,6 +203,9 @@ stm_output_disclaim(struct stm_device *stm, struct stm_output *output)
 {
 	struct stp_master *master = stm_master(stm, output->master);
 
+	lockdep_assert_held(&stm->mc_lock);
+	lockdep_assert_held(&output->lock);
+
 	bitmap_release_region(&master->chan_map[0], output->channel,
 			      ilog2(output->nr_chans));
 
@@ -233,7 +240,7 @@ static int find_free_channels(unsigned long *bitmap, unsigned int start,
 	return -1;
 }
 
-static unsigned int
+static int
 stm_find_master_chan(struct stm_device *stm, unsigned int width,
 		     unsigned int *mstart, unsigned int mend,
 		     unsigned int *cstart, unsigned int cend)
@@ -288,12 +295,13 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width,
 	}
 
 	spin_lock(&stm->mc_lock);
+	spin_lock(&output->lock);
 	/* output is already assigned -- shouldn't happen */
 	if (WARN_ON_ONCE(output->nr_chans))
 		goto unlock;
 
 	ret = stm_find_master_chan(stm, width, &midx, mend, &cidx, cend);
-	if (ret)
+	if (ret < 0)
 		goto unlock;
 
 	output->master = midx;
@@ -304,6 +312,7 @@ static int stm_output_assign(struct stm_device *stm, unsigned int width,
 
 	ret = 0;
 unlock:
+	spin_unlock(&output->lock);
 	spin_unlock(&stm->mc_lock);
 
 	return ret;
@@ -312,11 +321,18 @@ unlock:
 static void stm_output_free(struct stm_device *stm, struct stm_output *output)
 {
 	spin_lock(&stm->mc_lock);
+	spin_lock(&output->lock);
 	if (output->nr_chans)
 		stm_output_disclaim(stm, output);
+	spin_unlock(&output->lock);
 	spin_unlock(&stm->mc_lock);
 }
 
+static void stm_output_init(struct stm_output *output)
+{
+	spin_lock_init(&output->lock);
+}
+
 static int major_match(struct device *dev, const void *data)
 {
 	unsigned int major = *(unsigned int *)data;
@@ -339,6 +355,7 @@ static int stm_char_open(struct inode *inode, struct file *file)
 	if (!stmf)
 		return -ENOMEM;
 
+	stm_output_init(&stmf->output);
 	stmf->stm = to_stm_device(dev);
 
 	if (!try_module_get(stmf->stm->owner))
@@ -349,6 +366,8 @@ static int stm_char_open(struct inode *inode, struct file *file)
 	return nonseekable_open(inode, file);
 
 err_free:
+	/* matches class_find_device() above */
+	put_device(dev);
 	kfree(stmf);
 
 	return err;
@@ -357,9 +376,19 @@ err_free:
 static int stm_char_release(struct inode *inode, struct file *file)
 {
 	struct stm_file *stmf = file->private_data;
+	struct stm_device *stm = stmf->stm;
+
+	if (stm->data->unlink)
+		stm->data->unlink(stm->data, stmf->output.master,
+				  stmf->output.channel);
 
-	stm_output_free(stmf->stm, &stmf->output);
-	stm_put_device(stmf->stm);
+	stm_output_free(stm, &stmf->output);
+
+	/*
+	 * matches the stm_char_open()'s
+	 * class_find_device() + try_module_get()
+	 */
+	stm_put_device(stm);
 	kfree(stmf);
 
 	return 0;
@@ -380,8 +409,8 @@ static int stm_file_assign(struct stm_file *stmf, char *id, unsigned int width)
 	return ret;
 }
 
-static void stm_write(struct stm_data *data, unsigned int master,
-		      unsigned int channel, const char *buf, size_t count)
+static ssize_t stm_write(struct stm_data *data, unsigned int master,
+			  unsigned int channel, const char *buf, size_t count)
 {
 	unsigned int flags = STP_PACKET_TIMESTAMPED;
 	const unsigned char *p = buf, nil = 0;
@@ -393,9 +422,14 @@ static void stm_write(struct stm_data *data, unsigned int master,
 		sz = data->packet(data, master, channel, STP_PACKET_DATA, flags,
 				  sz, p);
 		flags = 0;
+
+		if (sz < 0)
+			break;
 	}
 
 	data->packet(data, master, channel, STP_PACKET_FLAG, 0, 0, &nil);
+
+	return pos;
 }
 
 static ssize_t stm_char_write(struct file *file, const char __user *buf,
@@ -406,6 +440,9 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
 	char *kbuf;
 	int err;
 
+	if (count + 1 > PAGE_SIZE)
+		count = PAGE_SIZE - 1;
+
 	/*
 	 * if no m/c have been assigned to this writer up to this
 	 * point, use "default" policy entry
@@ -430,8 +467,8 @@ static ssize_t stm_char_write(struct file *file, const char __user *buf,
 		return -EFAULT;
 	}
 
-	stm_write(stm->data, stmf->output.master, stmf->output.channel, kbuf,
-		  count);
+	count = stm_write(stm->data, stmf->output.master, stmf->output.channel,
+			  kbuf, count);
 
 	kfree(kbuf);
 
@@ -515,10 +552,8 @@ static int stm_char_policy_set_ioctl(struct stm_file *stmf, void __user *arg)
 		ret = stm->data->link(stm->data, stmf->output.master,
 				      stmf->output.channel);
 
-	if (ret) {
+	if (ret)
 		stm_output_free(stmf->stm, &stmf->output);
-		stm_put_device(stmf->stm);
-	}
 
 err_free:
 	kfree(id);
@@ -618,7 +653,7 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	if (!stm_data->packet || !stm_data->sw_nchannels)
 		return -EINVAL;
 
-	nmasters = stm_data->sw_end - stm_data->sw_start;
+	nmasters = stm_data->sw_end - stm_data->sw_start + 1;
 	stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL);
 	if (!stm)
 		return -ENOMEM;
@@ -641,6 +676,7 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	if (err)
 		goto err_device;
 
+	mutex_init(&stm->link_mutex);
 	spin_lock_init(&stm->link_lock);
 	INIT_LIST_HEAD(&stm->link_list);
 
@@ -654,6 +690,7 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data,
 	return 0;
 
 err_device:
+	/* matches device_initialize() above */
 	put_device(&stm->dev);
 err_free:
 	kfree(stm);
@@ -662,20 +699,28 @@ err_free:
 }
 EXPORT_SYMBOL_GPL(stm_register_device);
 
-static void __stm_source_link_drop(struct stm_source_device *src,
-				   struct stm_device *stm);
+static int __stm_source_link_drop(struct stm_source_device *src,
+				  struct stm_device *stm);
 
 void stm_unregister_device(struct stm_data *stm_data)
 {
 	struct stm_device *stm = stm_data->stm;
 	struct stm_source_device *src, *iter;
-	int i;
+	int i, ret;
 
-	spin_lock(&stm->link_lock);
+	mutex_lock(&stm->link_mutex);
 	list_for_each_entry_safe(src, iter, &stm->link_list, link_entry) {
-		__stm_source_link_drop(src, stm);
+		ret = __stm_source_link_drop(src, stm);
+		/*
+		 * src <-> stm link must not change under the same
+		 * stm::link_mutex, so complain loudly if it has;
+		 * also in this situation ret!=0 means this src is
+		 * not connected to this stm and it should be otherwise
+		 * safe to proceed with the tear-down of stm.
+		 */
+		WARN_ON_ONCE(ret);
 	}
-	spin_unlock(&stm->link_lock);
+	mutex_unlock(&stm->link_mutex);
 
 	synchronize_srcu(&stm_source_srcu);
 
@@ -686,7 +731,7 @@ void stm_unregister_device(struct stm_data *stm_data)
 		stp_policy_unbind(stm->policy);
 	mutex_unlock(&stm->policy_mutex);
 
-	for (i = 0; i < stm->sw_nmasters; i++)
+	for (i = stm->data->sw_start; i <= stm->data->sw_end; i++)
 		stp_master_free(stm, i);
 
 	device_unregister(&stm->dev);
@@ -694,6 +739,17 @@ void stm_unregister_device(struct stm_data *stm_data)
 }
 EXPORT_SYMBOL_GPL(stm_unregister_device);
 
+/*
+ * stm::link_list access serialization uses a spinlock and a mutex; holding
+ * either of them guarantees that the list is stable; modification requires
+ * holding both of them.
+ *
+ * Lock ordering is as follows:
+ *   stm::link_mutex
+ *     stm::link_lock
+ *       src::link_lock
+ */
+
 /**
  * stm_source_link_add() - connect an stm_source device to an stm device
  * @src:	stm_source device
@@ -710,6 +766,7 @@ static int stm_source_link_add(struct stm_source_device *src,
 	char *id;
 	int err;
 
+	mutex_lock(&stm->link_mutex);
 	spin_lock(&stm->link_lock);
 	spin_lock(&src->link_lock);
 
@@ -719,6 +776,7 @@ static int stm_source_link_add(struct stm_source_device *src,
 
 	spin_unlock(&src->link_lock);
 	spin_unlock(&stm->link_lock);
+	mutex_unlock(&stm->link_mutex);
 
 	id = kstrdup(src->data->name, GFP_KERNEL);
 	if (id) {
@@ -753,9 +811,9 @@ static int stm_source_link_add(struct stm_source_device *src,
 
 fail_free_output:
 	stm_output_free(stm, &src->output);
-	stm_put_device(stm);
 
 fail_detach:
+	mutex_lock(&stm->link_mutex);
 	spin_lock(&stm->link_lock);
 	spin_lock(&src->link_lock);
 
@@ -764,6 +822,7 @@ fail_detach:
 
 	spin_unlock(&src->link_lock);
 	spin_unlock(&stm->link_lock);
+	mutex_unlock(&stm->link_mutex);
 
 	return err;
 }
@@ -776,28 +835,55 @@ fail_detach:
  * If @stm is @src::link, disconnect them from one another and put the
  * reference on the @stm device.
  *
- * Caller must hold stm::link_lock.
+ * Caller must hold stm::link_mutex.
  */
-static void __stm_source_link_drop(struct stm_source_device *src,
-				   struct stm_device *stm)
+static int __stm_source_link_drop(struct stm_source_device *src,
+				  struct stm_device *stm)
 {
 	struct stm_device *link;
+	int ret = 0;
+
+	lockdep_assert_held(&stm->link_mutex);
 
+	/* for stm::link_list modification, we hold both mutex and spinlock */
+	spin_lock(&stm->link_lock);
 	spin_lock(&src->link_lock);
 	link = srcu_dereference_check(src->link, &stm_source_srcu, 1);
-	if (WARN_ON_ONCE(link != stm)) {
-		spin_unlock(&src->link_lock);
-		return;
+
+	/*
+	 * The linked device may have changed since we last looked, because
+	 * we weren't holding the src::link_lock back then; if this is the
+	 * case, tell the caller to retry.
+	 */
+	if (link != stm) {
+		ret = -EAGAIN;
+		goto unlock;
 	}
 
 	stm_output_free(link, &src->output);
-	/* caller must hold stm::link_lock */
 	list_del_init(&src->link_entry);
 	/* matches stm_find_device() from stm_source_link_store() */
 	stm_put_device(link);
 	rcu_assign_pointer(src->link, NULL);
 
+unlock:
 	spin_unlock(&src->link_lock);
+	spin_unlock(&stm->link_lock);
+
+	/*
+	 * Call the unlink callbacks for both source and stm, when we know
+	 * that we have actually performed the unlinking.
+	 */
+	if (!ret) {
+		if (src->data->unlink)
+			src->data->unlink(src->data);
+
+		if (stm->data->unlink)
+			stm->data->unlink(stm->data, src->output.master,
+					  src->output.channel);
+	}
+
+	return ret;
 }
 
 /**
@@ -813,21 +899,29 @@ static void __stm_source_link_drop(struct stm_source_device *src,
 static void stm_source_link_drop(struct stm_source_device *src)
 {
 	struct stm_device *stm;
-	int idx;
+	int idx, ret;
 
+retry:
 	idx = srcu_read_lock(&stm_source_srcu);
+	/*
+	 * The stm device will be valid for the duration of this
+	 * read section, but the link may change before we grab
+	 * the src::link_lock in __stm_source_link_drop().
+	 */
 	stm = srcu_dereference(src->link, &stm_source_srcu);
 
+	ret = 0;
 	if (stm) {
-		if (src->data->unlink)
-			src->data->unlink(src->data);
-
-		spin_lock(&stm->link_lock);
-		__stm_source_link_drop(src, stm);
-		spin_unlock(&stm->link_lock);
+		mutex_lock(&stm->link_mutex);
+		ret = __stm_source_link_drop(src, stm);
+		mutex_unlock(&stm->link_mutex);
 	}
 
 	srcu_read_unlock(&stm_source_srcu, idx);
+
+	/* if it did change, retry */
+	if (ret == -EAGAIN)
+		goto retry;
 }
 
 static ssize_t stm_source_link_show(struct device *dev,
@@ -862,8 +956,10 @@ static ssize_t stm_source_link_store(struct device *dev,
 		return -EINVAL;
 
 	err = stm_source_link_add(src, link);
-	if (err)
+	if (err) {
+		/* matches the stm_find_device() above */
 		stm_put_device(link);
+	}
 
 	return err ? : count;
 }
@@ -925,6 +1021,7 @@ int stm_source_register_device(struct device *parent,
 	if (err)
 		goto err;
 
+	stm_output_init(&src->output);
 	spin_lock_init(&src->link_lock);
 	INIT_LIST_HEAD(&src->link_entry);
 	src->data = data;
@@ -973,9 +1070,9 @@ int stm_source_write(struct stm_source_data *data, unsigned int chan,
 
 	stm = srcu_dereference(src->link, &stm_source_srcu);
 	if (stm)
-		stm_write(stm->data, src->output.master,
-			  src->output.channel + chan,
-			  buf, count);
+		count = stm_write(stm->data, src->output.master,
+				  src->output.channel + chan,
+				  buf, count);
 	else
 		count = -ENODEV;
 
diff --git a/drivers/hwtracing/stm/dummy_stm.c b/drivers/hwtracing/stm/dummy_stm.c
index 3709bef0b21f..310adf57e7a1 100644
--- a/drivers/hwtracing/stm/dummy_stm.c
+++ b/drivers/hwtracing/stm/dummy_stm.c
@@ -40,22 +40,75 @@ dummy_stm_packet(struct stm_data *stm_data, unsigned int master,
 	return size;
 }
 
-static struct stm_data dummy_stm = {
-	.name		= "dummy_stm",
-	.sw_start	= 0x0000,
-	.sw_end		= 0xffff,
-	.sw_nchannels	= 0xffff,
-	.packet		= dummy_stm_packet,
-};
+#define DUMMY_STM_MAX 32
+
+static struct stm_data dummy_stm[DUMMY_STM_MAX];
+
+static int nr_dummies = 4;
+
+module_param(nr_dummies, int, 0600);
+
+static unsigned int dummy_stm_nr;
+
+static unsigned int fail_mode;
+
+module_param(fail_mode, int, 0600);
+
+static int dummy_stm_link(struct stm_data *data, unsigned int master,
+			  unsigned int channel)
+{
+	if (fail_mode && (channel & fail_mode))
+		return -EINVAL;
+
+	return 0;
+}
 
 static int dummy_stm_init(void)
 {
-	return stm_register_device(NULL, &dummy_stm, THIS_MODULE);
+	int i, ret = -ENOMEM, __nr_dummies = ACCESS_ONCE(nr_dummies);
+
+	if (__nr_dummies < 0 || __nr_dummies > DUMMY_STM_MAX)
+		return -EINVAL;
+
+	for (i = 0; i < __nr_dummies; i++) {
+		dummy_stm[i].name = kasprintf(GFP_KERNEL, "dummy_stm.%d", i);
+		if (!dummy_stm[i].name)
+			goto fail_unregister;
+
+		dummy_stm[i].sw_start		= 0x0000;
+		dummy_stm[i].sw_end		= 0xffff;
+		dummy_stm[i].sw_nchannels	= 0xffff;
+		dummy_stm[i].packet		= dummy_stm_packet;
+		dummy_stm[i].link		= dummy_stm_link;
+
+		ret = stm_register_device(NULL, &dummy_stm[i], THIS_MODULE);
+		if (ret)
+			goto fail_free;
+	}
+
+	dummy_stm_nr = __nr_dummies;
+
+	return 0;
+
+fail_unregister:
+	for (i--; i >= 0; i--) {
+		stm_unregister_device(&dummy_stm[i]);
+fail_free:
+		kfree(dummy_stm[i].name);
+	}
+
+	return ret;
+
 }
 
 static void dummy_stm_exit(void)
 {
-	stm_unregister_device(&dummy_stm);
+	int i;
+
+	for (i = 0; i < dummy_stm_nr; i++) {
+		stm_unregister_device(&dummy_stm[i]);
+		kfree(dummy_stm[i].name);
+	}
 }
 
 module_init(dummy_stm_init);
diff --git a/drivers/hwtracing/stm/heartbeat.c b/drivers/hwtracing/stm/heartbeat.c
new file mode 100644
index 000000000000..0133571b506f
--- /dev/null
+++ b/drivers/hwtracing/stm/heartbeat.c
@@ -0,0 +1,130 @@
+/*
+ * Simple heartbeat STM source driver
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * Heartbeat STM source will send repetitive messages over STM devices to a
+ * trace host.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/hrtimer.h>
+#include <linux/slab.h>
+#include <linux/stm.h>
+
+#define STM_HEARTBEAT_MAX	32
+
+static int nr_devs = 4;
+static int interval_ms = 10;
+
+module_param(nr_devs, int, 0600);
+module_param(interval_ms, int, 0600);
+
+static struct stm_heartbeat {
+	struct stm_source_data	data;
+	struct hrtimer		hrtimer;
+	unsigned int		active;
+} stm_heartbeat[STM_HEARTBEAT_MAX];
+
+static unsigned int nr_instances;
+
+static const char str[] = "heartbeat stm source driver is here to serve you";
+
+static enum hrtimer_restart stm_heartbeat_hrtimer_handler(struct hrtimer *hr)
+{
+	struct stm_heartbeat *heartbeat = container_of(hr, struct stm_heartbeat,
+						       hrtimer);
+
+	stm_source_write(&heartbeat->data, 0, str, sizeof str);
+	if (heartbeat->active)
+		hrtimer_forward_now(hr, ms_to_ktime(interval_ms));
+
+	return heartbeat->active ? HRTIMER_RESTART : HRTIMER_NORESTART;
+}
+
+static int stm_heartbeat_link(struct stm_source_data *data)
+{
+	struct stm_heartbeat *heartbeat =
+		container_of(data, struct stm_heartbeat, data);
+
+	heartbeat->active = 1;
+	hrtimer_start(&heartbeat->hrtimer, ms_to_ktime(interval_ms),
+		      HRTIMER_MODE_ABS);
+
+	return 0;
+}
+
+static void stm_heartbeat_unlink(struct stm_source_data *data)
+{
+	struct stm_heartbeat *heartbeat =
+		container_of(data, struct stm_heartbeat, data);
+
+	heartbeat->active = 0;
+	hrtimer_cancel(&heartbeat->hrtimer);
+}
+
+static int stm_heartbeat_init(void)
+{
+	int i, ret = -ENOMEM, __nr_instances = ACCESS_ONCE(nr_devs);
+
+	if (__nr_instances < 0 || __nr_instances > STM_HEARTBEAT_MAX)
+		return -EINVAL;
+
+	for (i = 0; i < __nr_instances; i++) {
+		stm_heartbeat[i].data.name =
+			kasprintf(GFP_KERNEL, "heartbeat.%d", i);
+		if (!stm_heartbeat[i].data.name)
+			goto fail_unregister;
+
+		stm_heartbeat[i].data.nr_chans	= 1;
+		stm_heartbeat[i].data.link		= stm_heartbeat_link;
+		stm_heartbeat[i].data.unlink	= stm_heartbeat_unlink;
+		hrtimer_init(&stm_heartbeat[i].hrtimer, CLOCK_MONOTONIC,
+			     HRTIMER_MODE_ABS);
+		stm_heartbeat[i].hrtimer.function =
+			stm_heartbeat_hrtimer_handler;
+
+		ret = stm_source_register_device(NULL, &stm_heartbeat[i].data);
+		if (ret)
+			goto fail_free;
+	}
+
+	nr_instances = __nr_instances;
+
+	return 0;
+
+fail_unregister:
+	for (i--; i >= 0; i--) {
+		stm_source_unregister_device(&stm_heartbeat[i].data);
+fail_free:
+		kfree(stm_heartbeat[i].data.name);
+	}
+
+	return ret;
+}
+
+static void stm_heartbeat_exit(void)
+{
+	int i;
+
+	for (i = 0; i < nr_instances; i++) {
+		stm_source_unregister_device(&stm_heartbeat[i].data);
+		kfree(stm_heartbeat[i].data.name);
+	}
+}
+
+module_init(stm_heartbeat_init);
+module_exit(stm_heartbeat_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("stm_heartbeat driver");
+MODULE_AUTHOR("Alexander Shishkin <alexander.shishkin@linux.intel.com>");
diff --git a/drivers/hwtracing/stm/policy.c b/drivers/hwtracing/stm/policy.c
index 11ab6d01adf6..1db189657b2b 100644
--- a/drivers/hwtracing/stm/policy.c
+++ b/drivers/hwtracing/stm/policy.c
@@ -272,13 +272,17 @@ void stp_policy_unbind(struct stp_policy *policy)
 {
 	struct stm_device *stm = policy->stm;
 
+	/*
+	 * stp_policy_release() will not call here if the policy is already
+	 * unbound; other users should not either, as no link exists between
+	 * this policy and anything else in that case
+	 */
 	if (WARN_ON_ONCE(!policy->stm))
 		return;
 
-	mutex_lock(&stm->policy_mutex);
-	stm->policy = NULL;
-	mutex_unlock(&stm->policy_mutex);
+	lockdep_assert_held(&stm->policy_mutex);
 
+	stm->policy = NULL;
 	policy->stm = NULL;
 
 	stm_put_device(stm);
@@ -287,8 +291,16 @@ void stp_policy_unbind(struct stp_policy *policy)
 static void stp_policy_release(struct config_item *item)
 {
 	struct stp_policy *policy = to_stp_policy(item);
+	struct stm_device *stm = policy->stm;
 
+	/* a policy *can* be unbound and still exist in configfs tree */
+	if (!stm)
+		return;
+
+	mutex_lock(&stm->policy_mutex);
 	stp_policy_unbind(policy);
+	mutex_unlock(&stm->policy_mutex);
+
 	kfree(policy);
 }
 
@@ -320,10 +332,11 @@ stp_policies_make(struct config_group *group, const char *name)
 
 	/*
 	 * node must look like <device_name>.<policy_name>, where
-	 * <device_name> is the name of an existing stm device and
-	 * <policy_name> is an arbitrary string
+	 * <device_name> is the name of an existing stm device; may
+	 *               contain dots;
+	 * <policy_name> is an arbitrary string; may not contain dots
 	 */
-	p = strchr(devname, '.');
+	p = strrchr(devname, '.');
 	if (!p) {
 		kfree(devname);
 		return ERR_PTR(-EINVAL);
diff --git a/drivers/hwtracing/stm/stm.h b/drivers/hwtracing/stm/stm.h
index 95ece0292c99..4e8c6926260f 100644
--- a/drivers/hwtracing/stm/stm.h
+++ b/drivers/hwtracing/stm/stm.h
@@ -45,6 +45,7 @@ struct stm_device {
 	int			major;
 	unsigned int		sw_nmasters;
 	struct stm_data		*data;
+	struct mutex		link_mutex;
 	spinlock_t		link_lock;
 	struct list_head	link_list;
 	/* master allocation */
@@ -56,6 +57,7 @@ struct stm_device {
 	container_of((_d), struct stm_device, dev)
 
 struct stm_output {
+	spinlock_t		lock;
 	unsigned int		master;
 	unsigned int		channel;
 	unsigned int		nr_chans;