gpu: nvgpu: get VM reference for TSG

We store a reference to common address space of channels
in struct tsg_gk20a without increasing the refcount

This could result in freeing the address space even when
some channel in TSG needs it or when we need to free
common gr_ctx

Fix this by getting ref using gk20a_vm_get() when we store
the VM reference. We drop this reference with
gk20a_vm_put() when closing the TSG

Bug 1470692

Change-Id: Ifc1f29d32cd721810bfbb5a4db96095770318c17
Signed-off-by: Deepak Nibade <dnibade@nvidia.com>
Reviewed-on: http://git-master/r/495668
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Tested-by: Terje Bergstrom <tbergstrom@nvidia.com>

2 files changed, 6 insertions, 1 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/gr_gk20a.c b/drivers/gpu/nvgpu/gk20a/gr_gk20a.c
index 69fe4901..976e9171 100644
--- a/drivers/gpu/nvgpu/gk20a/gr_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/gr_gk20a.c
@@ -2830,10 +2830,13 @@ int gk20a_alloc_obj_ctx(struct channel_gk20a  *c,
         } else {
                 if (!tsg->tsg_gr_ctx) {
                         tsg->vm = c->vm;
+                        gk20a_vm_get(tsg->vm);
                         err = gr_gk20a_alloc_tsg_gr_ctx(g, tsg);
                         if (err) {
                                 gk20a_err(dev_from_gk20a(g),
                                         "fail to allocate TSG gr ctx buffer");
+                                gk20a_vm_put(tsg->vm);
+                                tsg->vm = NULL;
                                 goto out;
                         }
                 }
diff --git a/drivers/gpu/nvgpu/gk20a/tsg_gk20a.c b/drivers/gpu/nvgpu/gk20a/tsg_gk20a.c
index e7b70894..849c3f6a 100644
--- a/drivers/gpu/nvgpu/gk20a/tsg_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/tsg_gk20a.c
@@ -161,8 +161,10 @@ static void gk20a_tsg_release(struct kref *ref)
                 gr_gk20a_free_tsg_gr_ctx(tsg);
                 tsg->tsg_gr_ctx = NULL;
         }
-        if (tsg->vm)
+        if (tsg->vm) {
+                gk20a_vm_put(tsg->vm);
                 tsg->vm = NULL;
+        }
 
         release_used_tsg(&g->fifo, tsg);