shadow bo is the shadow of a bo, which is always in GTT,
which can be used to backup the original bo.
V2:
reference shadow parent, shadow bo will be freed by who allocted him.

Change-Id: Ia27d4225c47ff41d3053eb691276e29fb2d64026
Signed-off-by: Chunming Zhou <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_object.c | 48 ++++++++++++++++++++++++++++--
 include/uapi/drm/amdgpu_drm.h              |  2 ++
 3 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index 60247e5..04c88de 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -507,6 +507,7 @@ struct amdgpu_bo {
        struct amdgpu_device            *adev;
        struct drm_gem_object           gem_base;
        struct amdgpu_bo                *parent;
+       struct amdgpu_bo                *shadow;
 
        struct ttm_bo_kmap_obj          dma_buf_vmap;
        struct amdgpu_mn                *mn;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
index d8e69a7..278017d 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_object.c
@@ -380,6 +380,37 @@ fail_free:
        return r;
 }
 
+static int amdgpu_bo_create_shadow(struct amdgpu_device *adev,
+                                  unsigned long size, int byte_align,
+                                  struct amdgpu_bo *bo)
+{
+       struct ttm_placement placement = {0};
+       struct ttm_place placements[AMDGPU_GEM_DOMAIN_MAX + 1];
+       int r;
+
+       if (bo->shadow)
+               return 0;
+
+       bo->flags |= AMDGPU_GEM_CREATE_SHADOW;
+       memset(&placements, 0,
+              (AMDGPU_GEM_DOMAIN_MAX + 1) * sizeof(struct ttm_place));
+
+       amdgpu_ttm_placement_init(adev, &placement,
+                                 placements, AMDGPU_GEM_DOMAIN_GTT,
+                                 AMDGPU_GEM_CREATE_CPU_GTT_USWC);
+
+       r = amdgpu_bo_create_restricted(adev, size, byte_align, true,
+                                       AMDGPU_GEM_DOMAIN_GTT,
+                                       AMDGPU_GEM_CREATE_CPU_GTT_USWC,
+                                       NULL, &placement,
+                                       bo->tbo.resv,
+                                       &bo->shadow);
+       if (!r)
+               bo->shadow->parent = amdgpu_bo_ref(bo);
+
+       return r;
+}
+
 int amdgpu_bo_create(struct amdgpu_device *adev,
                     unsigned long size, int byte_align,
                     bool kernel, u32 domain, u64 flags,
@@ -389,6 +420,7 @@ int amdgpu_bo_create(struct amdgpu_device *adev,
 {
        struct ttm_placement placement = {0};
        struct ttm_place placements[AMDGPU_GEM_DOMAIN_MAX + 1];
+       int r;
 
        memset(&placements, 0,
               (AMDGPU_GEM_DOMAIN_MAX + 1) * sizeof(struct ttm_place));
@@ -396,9 +428,19 @@ int amdgpu_bo_create(struct amdgpu_device *adev,
        amdgpu_ttm_placement_init(adev, &placement,
                                  placements, domain, flags);
 
-       return amdgpu_bo_create_restricted(adev, size, byte_align, kernel,
-                                          domain, flags, sg, &placement,
-                                          resv, bo_ptr);
+       r = amdgpu_bo_create_restricted(adev, size, byte_align, kernel,
+                                       domain, flags, sg, &placement,
+                                       resv, bo_ptr);
+       if (r)
+               return r;
+
+       if (flags & AMDGPU_GEM_CREATE_SHADOW) {
+               r = amdgpu_bo_create_shadow(adev, size, byte_align, (*bo_ptr));
+               if (r)
+                       amdgpu_bo_unref(bo_ptr);
+       }
+
+       return r;
 }
 
 int amdgpu_bo_kmap(struct amdgpu_bo *bo, void **ptr)
diff --git a/include/uapi/drm/amdgpu_drm.h b/include/uapi/drm/amdgpu_drm.h
index 8df3816..da2d3e1 100644
--- a/include/uapi/drm/amdgpu_drm.h
+++ b/include/uapi/drm/amdgpu_drm.h
@@ -77,6 +77,8 @@
 #define AMDGPU_GEM_CREATE_CPU_GTT_USWC         (1 << 2)
 /* Flag that the memory should be in VRAM and cleared */
 #define AMDGPU_GEM_CREATE_VRAM_CLEARED         (1 << 3)
+/* Flag that create shadow bo(GTT) while allocating vram bo */
+#define AMDGPU_GEM_CREATE_SHADOW               (1 << 4)
 
 struct drm_amdgpu_gem_create_in  {
        /** the requested memory size */
-- 
1.9.1

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