[PATCH AUTOSEL for 4.9 021/293] coresight: Fix reference count for software sources

[Sasha Levin]

From: Suzuki K Poulose 

[ Upstream commit 022aa1a81b778789ee7cf3124595854276a0330d ]

For software sources (i.e STM), there could be multiple agents
generating the trace data, unlike the ETMs. So we need to
properly do the accounting for the active number of users
to disable the device when the last user goes away. Right
now, the reference counting is broken for sources as we skip
the actions when we detect that the source is enabled.

This patch fixes the problem by adding the refcounting for
software sources, even when they are enabled.

Cc: Mathieu Poirier 
Reported-by: Robert Walker 
Signed-off-by: Suzuki K Poulose 
Signed-off-by: Mathieu Poirier 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin 
---
 drivers/hwtracing/coresight/coresight.c | 15 +--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c 
b/drivers/hwtracing/coresight/coresight.c
index 7bf00a0beb6f..4383324ec01c 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -498,6 +498,9 @@ int coresight_enable(struct coresight_device *csdev)
 {
int cpu, ret = 0;
struct list_head *path;
+   enum coresight_dev_subtype_source subtype;
+
+   subtype = csdev->subtype.source_subtype;
 
mutex_lock(_mutex);
 
@@ -505,8 +508,16 @@ int coresight_enable(struct coresight_device *csdev)
if (ret)
goto out;
 
-   if (csdev->enable)
+   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;
+   }
 
path = coresight_build_path(csdev);
if (IS_ERR(path)) {
@@ -523,7 +534,7 @@ int coresight_enable(struct coresight_device *csdev)
if (ret)
goto err_source;
 
-   switch (csdev->subtype.source_subtype) {
+   switch (subtype) {
case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
/*
 * When working from sysFS it is important to keep track
-- 
2.15.1

[PATCH AUTOSEL for 4.9 021/293] coresight: Fix reference count for software sources

[Sasha Levin]

From: Suzuki K Poulose 

[ Upstream commit 022aa1a81b778789ee7cf3124595854276a0330d ]

For software sources (i.e STM), there could be multiple agents
generating the trace data, unlike the ETMs. So we need to
properly do the accounting for the active number of users
to disable the device when the last user goes away. Right
now, the reference counting is broken for sources as we skip
the actions when we detect that the source is enabled.

This patch fixes the problem by adding the refcounting for
software sources, even when they are enabled.

Cc: Mathieu Poirier 
Reported-by: Robert Walker 
Signed-off-by: Suzuki K Poulose 
Signed-off-by: Mathieu Poirier 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Sasha Levin 
---
 drivers/hwtracing/coresight/coresight.c | 15 +--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight.c 
b/drivers/hwtracing/coresight/coresight.c
index 7bf00a0beb6f..4383324ec01c 100644
--- a/drivers/hwtracing/coresight/coresight.c
+++ b/drivers/hwtracing/coresight/coresight.c
@@ -498,6 +498,9 @@ int coresight_enable(struct coresight_device *csdev)
 {
int cpu, ret = 0;
struct list_head *path;
+   enum coresight_dev_subtype_source subtype;
+
+   subtype = csdev->subtype.source_subtype;
 
mutex_lock(_mutex);
 
@@ -505,8 +508,16 @@ int coresight_enable(struct coresight_device *csdev)
if (ret)
goto out;
 
-   if (csdev->enable)
+   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;
+   }
 
path = coresight_build_path(csdev);
if (IS_ERR(path)) {
@@ -523,7 +534,7 @@ int coresight_enable(struct coresight_device *csdev)
if (ret)
goto err_source;
 
-   switch (csdev->subtype.source_subtype) {
+   switch (subtype) {
case CORESIGHT_DEV_SUBTYPE_SOURCE_PROC:
/*
 * When working from sysFS it is important to keep track
-- 
2.15.1