gpu: nvgpu: add refcounting for TSG

Add refcounting for TSGs and manage the refcounts as below :
- initialize ref when TSG is opened
- get ref when channel is bound to TSG
- drop the ref when channel is unbound (i.e. during channel close)
- drop the ref when TSG is closed
- when refcount drops to zero, we free the TSG

This refcounting makes it possible to close channels or TSG
in any order

Bug 1470692

Change-Id: Ia4b39164a4582c8169da62a91b9131094c67f5f8
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/495667
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/tsg_gk20a.h b/drivers/gpu/nvgpu/gk20a/tsg_gk20a.h
index dd8679be..4ad02996 100644
--- a/drivers/gpu/nvgpu/gk20a/tsg_gk20a.h
+++ b/drivers/gpu/nvgpu/gk20a/tsg_gk20a.h
@@ -35,6 +35,8 @@ struct tsg_gk20a {
         bool in_use;
         int tsgid;
 
+        struct kref refcount;
+
         struct list_head ch_list;
         int num_active_channels;
         struct mutex ch_list_lock;