gpu: nvgpu: Simplify ref-counting on VMs

Simplify ref-counting on VMs: take a ref when a VM is bound to a
channel and drop a ref when a channel is freed.

Previously ref-counts were scattered over the driver. Also the CE
and CDE code would bind channels with custom rolled code. This was
because the gk20a_vm_bind_channel() function took an as_share as
the VM argument (the VM was then inferred from that as_share).
However, it is trivial to abtract that bit out and allow a central
bind channel function that just takes a VM and a channel.

Bug 1846718

Change-Id: I156aab259f6c7a2fa338408c6c4a3a464cd44a0c
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: http://git-master/r/1261886
Reviewed-by: Richard Zhao <rizhao@nvidia.com>
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

1 files changed, 11 insertions, 10 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/mm_gk20a.c b/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
index e589e312..ea5ea73f 100644
--- a/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/mm_gk20a.c
@@ -4199,10 +4199,8 @@ static int gk20a_init_sema_pool(struct vm_gk20a *vm)
                 return -ENOMEM;
 
         vm->sema_pool = gk20a_semaphore_pool_alloc(sema_sea);
-        if (!vm->sema_pool) {
-                gk20a_vm_put(vm);
+        if (!vm->sema_pool)
                 return -ENOMEM;
-        }
 
         /*
          * Allocate a chunk of GPU VA space for mapping the semaphores. We will
@@ -4227,7 +4225,7 @@ static int gk20a_init_sema_pool(struct vm_gk20a *vm)
                 gk20a_semaphore_pool_unmap(vm->sema_pool, vm);
                 nvgpu_free(vm->vma[gmmu_page_size_small],
                            vm->sema_pool->gpu_va);
-                gk20a_vm_put(vm);
+                return err;
         }
 
         return 0;
@@ -4632,12 +4630,10 @@ int gk20a_vm_release_share(struct gk20a_as_share *as_share)
         gk20a_dbg_fn("");
 
         vm->as_share = NULL;
+        as_share->vm = NULL;
 
-        /* put as reference to vm */
         gk20a_vm_put(vm);
 
-        as_share->vm = NULL;
-
         return 0;
 }
 
@@ -4792,14 +4788,13 @@ int gk20a_vm_free_space(struct gk20a_as_share *as_share,
         return err;
 }
 
-int gk20a_vm_bind_channel(struct gk20a_as_share *as_share,
-                          struct channel_gk20a *ch)
+int __gk20a_vm_bind_channel(struct vm_gk20a *vm, struct channel_gk20a *ch)
 {
         int err = 0;
-        struct vm_gk20a *vm = as_share->vm;
 
         gk20a_dbg_fn("");
 
+        gk20a_vm_get(vm);
         ch->vm = vm;
         err = channel_gk20a_commit_va(ch);
         if (err)
@@ -4808,6 +4803,12 @@ int gk20a_vm_bind_channel(struct gk20a_as_share *as_share,
         return err;
 }
 
+int gk20a_vm_bind_channel(struct gk20a_as_share *as_share,
+                          struct channel_gk20a *ch)
+{
+        return __gk20a_vm_bind_channel(as_share->vm, ch);
+}
+
 int gk20a_dmabuf_alloc_drvdata(struct dma_buf *dmabuf, struct device *dev)
 {
         struct gk20a_dmabuf_priv *priv;