gpu: nvgpu: VM unmap refactoring

Re-organize the unmap code to be better split between OS specific
requirements and common core requirements. The new code flow works
as follows:

  nvgpu_vm_unmap()

Is the primary entrance to the unmap path. It takes a VM and a GPU
virtual address to unmap. There's also an optional batch mapping
struct.

This function is responsible for making sure there is a real buffer
and that if it's being called on a fixed mapping then the mapping
will definitely be freed (since buffers are ref-counted). Then this
function decrements the ref-count and returns.

If the ref-count hits zero then __nvgpu_vm_unmap_ref() is called
which just calls __nvgpu_vm_unmap() with the relevant batch struct
if present. This is where the real work is done. __nvgpu_vm_unmap()
clears the GMMU mapping, removes the mapped buffer from the various
lists and trees it may be in and then calls the
nvgpu_vm_unmap_system() function. This function handles any OS
specific stuff and must be defined by all VM OS implementations.

There's a a short cut used by some other core VM code to free
mappings without going through nvgpu_vm_map(). Mostly they just
directly decrement the mapping ref-count which can then call
__nvgpu_vm_unmap_ref() if the ref-count hits zero.

JIRA NVGPU-30
JIRA NVGPU-71

Change-Id: Ic626d37ab936819841bab45214f027b40ffa4e5a
Signed-off-by: Alex Waterman <alexw@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1583982
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>
Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com>
Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>

2 files changed, 12 insertions, 8 deletions

diff --git a/drivers/gpu/nvgpu/include/nvgpu/linux/vm.h b/drivers/gpu/nvgpu/include/nvgpu/linux/vm.h
index 7aacf496..3d9f9ea6 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/linux/vm.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/linux/vm.h
@@ -98,10 +98,6 @@ int nvgpu_vm_map_buffer(struct vm_gk20a *vm,
                         u64 mapping_size,
                         struct vm_gk20a_mapping_batch *batch);
 
-/* Note: batch may be NULL if unmap op is not part of a batch */
-int nvgpu_vm_unmap_buffer(struct vm_gk20a *vm, u64 offset,
-                          struct vm_gk20a_mapping_batch *batch);
-
 /* find buffer corresponding to va */
 int nvgpu_vm_find_buf(struct vm_gk20a *vm, u64 gpu_va,
                       struct dma_buf **dmabuf,
diff --git a/drivers/gpu/nvgpu/include/nvgpu/vm.h b/drivers/gpu/nvgpu/include/nvgpu/vm.h
index e529512b..84c7e0c7 100644
--- a/drivers/gpu/nvgpu/include/nvgpu/vm.h
+++ b/drivers/gpu/nvgpu/include/nvgpu/vm.h
@@ -207,11 +207,19 @@ void nvgpu_vm_put_buffers(struct vm_gk20a *vm,
                           struct nvgpu_mapped_buf **mapped_buffers,
                           int num_buffers);
 
-void nvgpu_vm_unmap_locked(struct nvgpu_mapped_buf *mapped_buffer,
-                           struct vm_gk20a_mapping_batch *batch);
-void nvgpu_vm_unmap_locked_ref(struct nvgpu_ref *ref);
+void nvgpu_vm_unmap(struct vm_gk20a *vm, u64 offset,
+                    struct vm_gk20a_mapping_batch *batch);
 
-void nvgpu_vm_unmap(struct vm_gk20a *vm, u64 offset);
+/*
+ * Implemented by each OS. Called from within the core VM code to handle OS
+ * specific components of an nvgpu_mapped_buf.
+ */
+void nvgpu_vm_unmap_system(struct nvgpu_mapped_buf *mapped_buffer);
+
+/*
+ * Don't use this outside of the core VM code!
+ */
+void __nvgpu_vm_unmap_ref(struct nvgpu_ref *ref);
 
 /*
  * These all require the VM update lock to be held.