[PATCH v3 15/20] coresight: tmc-etr: Introduce the notion of reference counting to ETR devices

[Mathieu Poirier]

This patch adds reference counting to struct etr_buf so that, in CPU-wide
trace scenarios, shared buffers can be disposed of when no longer used.

Signed-off-by: Mathieu Poirier <mathieu.poir...@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++++
 drivers/hwtracing/coresight/coresight-tmc.h     | 3 +++
 2 files changed, 8 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c 
b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index e1774d4bb5f3..1346474ac019 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -8,6 +8,7 @@
 #include <linux/coresight.h>
 #include <linux/dma-mapping.h>
 #include <linux/iommu.h>
+#include <linux/refcount.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/vmalloc.h>
@@ -1221,7 +1222,11 @@ get_perf_etr_buf_per_thread(struct tmc_drvdata *drvdata,
         * with memory allocation.
         */
        etr_buf = alloc_etr_buf(drvdata, event, nr_pages, pages, snapshot);
+       if (IS_ERR(etr_buf))
+               goto out;
 
+       refcount_set(&etr_buf->refcount, 1);
+out:
        return etr_buf;
 }
 
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h 
b/drivers/hwtracing/coresight/coresight-tmc.h
index 487c53701e9c..ee44906dffe8 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -9,6 +9,7 @@
 
 #include <linux/dma-mapping.h>
 #include <linux/miscdevice.h>
+#include <linux/refcount.h>
 
 #define TMC_RSZ                        0x004
 #define TMC_STS                        0x00c
@@ -133,6 +134,7 @@ struct etr_buf_operations;
 
 /**
  * struct etr_buf - Details of the buffer used by ETR
+ * refcount    ; Number of sources currently using this etr_buf.
  * @mode       : Mode of the ETR buffer, contiguous, Scatter Gather etc.
  * @full       : Trace data overflow
  * @size       : Size of the buffer.
@@ -143,6 +145,7 @@ struct etr_buf_operations;
  * @private    : Backend specific information for the buf
  */
 struct etr_buf {
+       refcount_t                      refcount;
        enum etr_mode                   mode;
        bool                            full;
        ssize_t                         size;
-- 
2.17.1