drm/ttm: move ttm_tt_{add, clear}_mapping into amdgpu

Now that setting page->index shouldn't be needed anymore, we are just
left with setting page->mapping, and here it looks like amdgpu is the
only user, where pointing the page->mapping at the dev_mapping is used
to verify that the pages do indeed belong to the device, if userspace
later tries to touch them.

v2(Christian):
  - Drop the functions altogether and just inline modifying
    the page->mapping

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210927114114.152310-3-matthew.auld@intel.com
Signed-off-by: Christian König <christian.koenig@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -1119,6 +1119,8 @@ static int amdgpu_ttm_tt_populate(struct ttm_device *bdev,
 {
 	struct amdgpu_device *adev = amdgpu_ttm_adev(bdev);
 	struct amdgpu_ttm_tt *gtt = (void *)ttm;
+	pgoff_t i;
+	int ret;
 
 	/* user pages are bound by amdgpu_ttm_tt_pin_userptr() */
 	if (gtt->userptr) {
@@ -1131,7 +1133,14 @@ static int amdgpu_ttm_tt_populate(struct ttm_device *bdev,
 	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
 		return 0;
 
-	return ttm_pool_alloc(&adev->mman.bdev.pool, ttm, ctx);
+	ret = ttm_pool_alloc(&adev->mman.bdev.pool, ttm, ctx);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ttm->num_pages; ++i)
+		ttm->pages[i]->mapping = bdev->dev_mapping;
+
+	return 0;
 }
 
 /*
@@ -1145,6 +1154,7 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_device *bdev,
 {
 	struct amdgpu_ttm_tt *gtt = (void *)ttm;
 	struct amdgpu_device *adev;
+	pgoff_t i;
 
 	amdgpu_ttm_backend_unbind(bdev, ttm);
 
@@ -1158,6 +1168,9 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_device *bdev,
 	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
 		return;
 
+	for (i = 0; i < ttm->num_pages; ++i)
+		ttm->pages[i]->mapping = NULL;
+
 	adev = amdgpu_ttm_adev(bdev);
 	return ttm_pool_free(&adev->mman.bdev.pool, ttm);
 }

drivers/gpu/drm/ttm/ttm_tt.c

@@ -289,17 +289,6 @@ int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm,
 	return ret;
 }
 
-static void ttm_tt_add_mapping(struct ttm_device *bdev, struct ttm_tt *ttm)
-{
-	pgoff_t i;
-
-	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
-		return;
-
-	for (i = 0; i < ttm->num_pages; ++i)
-		ttm->pages[i]->mapping = bdev->dev_mapping;
-}
-
 int ttm_tt_populate(struct ttm_device *bdev,
 		    struct ttm_tt *ttm, struct ttm_operation_ctx *ctx)
 {
@@ -336,7 +325,6 @@ int ttm_tt_populate(struct ttm_device *bdev,
 	if (ret)
 		goto error;
 
-	ttm_tt_add_mapping(bdev, ttm);
 	ttm->page_flags |= TTM_PAGE_FLAG_PRIV_POPULATED;
 	if (unlikely(ttm->page_flags & TTM_PAGE_FLAG_SWAPPED)) {
 		ret = ttm_tt_swapin(ttm);
@@ -359,24 +347,11 @@ int ttm_tt_populate(struct ttm_device *bdev,
 }
 EXPORT_SYMBOL(ttm_tt_populate);
 
-static void ttm_tt_clear_mapping(struct ttm_tt *ttm)
-{
-	pgoff_t i;
-	struct page **page = ttm->pages;
-
-	if (ttm->page_flags & TTM_PAGE_FLAG_SG)
-		return;
-
-	for (i = 0; i < ttm->num_pages; ++i)
-		(*page)->mapping = NULL;
-}
-
 void ttm_tt_unpopulate(struct ttm_device *bdev, struct ttm_tt *ttm)
 {
 	if (!ttm_tt_is_populated(ttm))
 		return;
 
-	ttm_tt_clear_mapping(ttm);
 	if (bdev->funcs->ttm_tt_unpopulate)
 		bdev->funcs->ttm_tt_unpopulate(bdev, ttm);
 	else