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, 5 insertions, 13 deletions

diff --git a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
index e272b130..c8b1c105 100644
--- a/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
+++ b/drivers/gpu/nvgpu/gk20a/channel_gk20a.c
@@ -1008,11 +1008,10 @@ static void gk20a_free_channel(struct channel_gk20a *ch, bool force)
         if (ch->hw_sema)
                 gk20a_semaphore_free_hw_sema(ch);
 
-        /* release channel binding to the as_share */
-        if (ch_vm->as_share)
-                gk20a_as_release_share(ch_vm->as_share);
-        else
-                gk20a_vm_put(ch_vm);
+        /*
+         * When releasing the channel we unbind the VM - so release the ref.
+         */
+        gk20a_vm_put(ch_vm);
 
         spin_lock(&ch->update_fn_lock);
         ch->update_fn = NULL;
@@ -2252,14 +2251,11 @@ static int gk20a_channel_add_job(struct channel_gk20a *c,
         int err = 0, num_mapped_buffers = 0;
         bool pre_alloc_enabled = channel_gk20a_is_prealloc_enabled(c);
 
-        /* job needs reference to this vm (released in channel_update) */
-        gk20a_vm_get(vm);
-
         if (!skip_buffer_refcounting) {
                 err = gk20a_vm_get_buffers(vm, &mapped_buffers,
                                         &num_mapped_buffers);
                 if (err)
-                        goto err_put_vm;
+                        return err;
         }
 
         /* put() is done in gk20a_channel_update() when the job is done */
@@ -2293,8 +2289,6 @@ static int gk20a_channel_add_job(struct channel_gk20a *c,
 
 err_put_buffers:
         gk20a_vm_put_buffers(vm, mapped_buffers, num_mapped_buffers);
-err_put_vm:
-        gk20a_vm_put(vm);
 
         return err;
 }
@@ -2385,8 +2379,6 @@ static void gk20a_channel_clean_up_jobs(struct channel_gk20a *c,
                 gk20a_free_priv_cmdbuf(c, job->wait_cmd);
                 gk20a_free_priv_cmdbuf(c, job->incr_cmd);
 
-                /* job is done. release its vm reference (taken in add_job) */
-                gk20a_vm_put(vm);
                 /* another bookkeeping taken in add_job. caller must hold a ref
                  * so this wouldn't get freed here. */
                 gk20a_channel_put(c);