gpu: nvgpu: Replace kref for refcounting in nvgpu

- added wrapper struct nvgpu_ref over nvgpu_atomic_t
- added nvgpu_ref_* APIs to access the above struct

JIRA NVGPU-140

Change-Id: Id47f897995dd4721751f7610b6d4d4fbfe4d6b9a
Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1540899
Reviewed-by: svc-mobile-coverity <svc-mobile-coverity@nvidia.com>
Reviewed-by: svccoveritychecker <svccoveritychecker@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Konsta Holtta <kholtta@nvidia.com>
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>

5 files changed, 82 insertions, 7 deletions

diff --git a/drivers/gpu/nvgpu/include/nvgpu/atomic.h b/drivers/gpu/nvgpu/include/nvgpu/atomic.h
index c7a5fcd9..393a9d35 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/atomic.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/atomic.h
@@ -61,10 +61,18 @@ static inline bool nvgpu_atomic_dec_and_test(nvgpu_atomic_t *v)
 {
         return __nvgpu_atomic_dec_and_test(v);
 }
+static inline bool nvgpu_atomic_sub_and_test(int i, nvgpu_atomic_t *v)
+{
+        return __nvgpu_atomic_sub_and_test(i, v);
+}
 static inline int nvgpu_atomic_add_return(int i, nvgpu_atomic_t *v)
 {
         return __nvgpu_atomic_add_return(i, v);
 }
+static inline int nvgpu_atomic_add_unless(nvgpu_atomic_t *v, int a, int u)
+{
+        return __nvgpu_atomic_add_unless(v, a, u);
+}
 static inline void nvgpu_atomic64_set(nvgpu_atomic64_t *v, long i)
 {
         return  __nvgpu_atomic64_set(v, i);
diff --git a/drivers/gpu/nvgpu/include/nvgpu/kref.h b/drivers/gpu/nvgpu/include/nvgpu/kref.h
index d24db603..fd2b456f 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/kref.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/kref.h
@@ -10,11 +10,68 @@
  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  * more details.
  */
+
+/*
+ * The following structure is used for reference counting of objects in nvgpu.
+ */
 #ifndef __NVGPU_KREF_H__
 #define __NVGPU_KREF_H__
 
-#ifdef __KERNEL__
-#include <linux/kref.h>
-#endif
+#include <nvgpu/atomic.h>
+
+struct nvgpu_ref {
+        nvgpu_atomic_t refcount;
+};
+
+/*
+ * Initialize object.
+ * @ref: the nvgpu_ref object to initialize
+ */
+static inline void nvgpu_ref_init(struct nvgpu_ref *ref)
+{
+        nvgpu_atomic_set(&ref->refcount, 1);
+}
+
+/*
+ * Increment reference count for the object
+ * @ref: the nvgpu_ref object
+ */
+static inline void nvgpu_ref_get(struct nvgpu_ref *ref)
+{
+        nvgpu_atomic_inc(&ref->refcount);
+}
+
+/*
+ * Decrement reference count for the object and call release() if it becomes
+ * zero.
+ * @ref: the nvgpu_ref object
+ * @release: pointer to the function that would be invoked to clean up the
+ *      object when the reference count becomes zero, i.e. the last
+ *      reference corresponding to this object is removed.
+ * Return 1 if object was removed, otherwise return 0. The user should not
+ * make any assumptions about the status of the object in the memory when
+ * the function returns 0 and should only use it to know that there are no
+ * further references to this object.
+ */
+static inline int nvgpu_ref_put(struct nvgpu_ref *ref,
+                void (*release)(struct nvgpu_ref *r))
+{
+        if (nvgpu_atomic_sub_and_test(1, &ref->refcount)) {
+                if (release != NULL)
+                        release(ref);
+                return 1;
+        }
+        return 0;
+}
+
+/*
+ * Increment reference count for the object unless it is zero.
+ * @ref: the nvgpu_ref object
+ * Return non-zero if the increment succeeds, Otherwise return 0.
+ */
+static inline int __must_check nvgpu_ref_get_unless_zero(struct nvgpu_ref *ref)
+{
+        return nvgpu_atomic_add_unless(&ref->refcount, 1, 0);
+}
 
 #endif /* __NVGPU_KREF_H__ */
diff --git a/drivers/gpu/nvgpu/include/nvgpu/linux/atomic.h b/drivers/gpu/nvgpu/include/nvgpu/linux/atomic.h
index 1fdb2674..0734672e 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/linux/atomic.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/linux/atomic.h
@@ -81,11 +81,21 @@ static inline bool __nvgpu_atomic_dec_and_test(nvgpu_atomic_t *v)
         return atomic_dec_and_test(&v->atomic_var);
 }
 
+static inline bool __nvgpu_atomic_sub_and_test(int i, nvgpu_atomic_t *v)
+{
+        return atomic_sub_and_test(i, &v->atomic_var);
+}
+
 static inline int __nvgpu_atomic_add_return(int i, nvgpu_atomic_t *v)
 {
         return atomic_add_return(i, &v->atomic_var);
 }
 
+static inline int __nvgpu_atomic_add_unless(nvgpu_atomic_t *v, int a, int u)
+{
+        return atomic_add_unless(&v->atomic_var, a, u);
+}
+
 static inline void __nvgpu_atomic64_set(nvgpu_atomic64_t *v, long i)
 {
         atomic64_set(&v->atomic_var, i);
diff --git a/drivers/gpu/nvgpu/include/nvgpu/semaphore.h b/drivers/gpu/nvgpu/include/nvgpu/semaphore.h
index 90261d81..5c0019ae 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/semaphore.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/semaphore.h
@@ -73,7 +73,7 @@ struct nvgpu_semaphore {
         nvgpu_atomic_t value;
         int incremented;
 
-        struct kref ref;
+        struct nvgpu_ref ref;
 };
 
 /*
@@ -106,7 +106,7 @@ struct nvgpu_semaphore_pool {
          * done waiting on it. This ref count ensures that the pool doesn't
          * go away until all semaphores using this pool are cleaned up first.
          */
-        struct kref ref;
+        struct nvgpu_ref ref;
 };
 
 static inline struct nvgpu_semaphore_pool *
diff --git a/drivers/gpu/nvgpu/include/nvgpu/vm.h b/drivers/gpu/nvgpu/include/nvgpu/vm.h
index 255b4361..b5c64c99 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/vm.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/vm.h
@@ -88,7 +88,7 @@ struct nvgpu_mapped_buf {
         u64 size;
         struct dma_buf *dmabuf;
         struct sg_table *sgt;
-        struct kref ref;
+        struct nvgpu_ref ref;
         u32 user_mapped;
         bool own_mem_ref;
         u32 pgsz_idx;
@@ -142,7 +142,7 @@ struct vm_gk20a {
 
         const struct gk20a_mmu_level *mmu_levels;
 
-        struct kref ref;
+        struct nvgpu_ref ref;
 
         struct nvgpu_mutex update_gmmu_lock;