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/

1 files changed, 136 insertions, 39 deletions

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;