drm/amdgpu: new resource cursor (v2)

Allows to walk over the drm_mm nodes in a TTM resource object.

v2: squash in fix from Felix
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Oak Zeng <Oak.Zeng@amd.com>
Tested-by: Nirmoy Das <nirmoy.das@amd.com>
Reviewed-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_res_cursor.h

+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright 2020 Advanced Micro Devices, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Authors: Christian König
+ */
+
+#ifndef __AMDGPU_RES_CURSOR_H__
+#define __AMDGPU_RES_CURSOR_H__
+
+#include <drm/drm_mm.h>
+#include <drm/ttm/ttm_resource.h>
+
+/* state back for walking over vram_mgr and gtt_mgr allocations */
+struct amdgpu_res_cursor {
+	uint64_t		start;
+	uint64_t		size;
+	uint64_t		remaining;
+	struct drm_mm_node	*node;
+};
+
+/**
+ * amdgpu_res_first - initialize a amdgpu_res_cursor
+ *
+ * @res: TTM resource object to walk
+ * @start: Start of the range
+ * @size: Size of the range
+ * @cur: cursor object to initialize
+ *
+ * Start walking over the range of allocations between @start and @size.
+ */
+static inline void amdgpu_res_first(struct ttm_resource *res,
+				    uint64_t start, uint64_t size,
+				    struct amdgpu_res_cursor *cur)
+{
+	struct drm_mm_node *node;
+
+	if (!res || !res->mm_node) {
+		cur->start = start;
+		cur->size = size;
+		cur->remaining = size;
+		cur->node = NULL;
+		return;
+	}
+
+	BUG_ON(start + size > res->num_pages << PAGE_SHIFT);
+
+	node = res->mm_node;
+	while (start > node->size << PAGE_SHIFT)
+		start -= node++->size << PAGE_SHIFT;
+
+	cur->start = (node->start << PAGE_SHIFT) + start;
+	cur->size = min((node->size << PAGE_SHIFT) - start, size);
+	cur->remaining = size;
+	cur->node = node;
+}
+
+/**
+ * amdgpu_res_next - advance the cursor
+ *
+ * @cur: the cursor to advance
+ * @size: number of bytes to move forward
+ *
+ * Move the cursor @size bytes forwrad, walking to the next node if necessary.
+ */
+static inline void amdgpu_res_next(struct amdgpu_res_cursor *cur, uint64_t size)
+{
+	struct drm_mm_node *node = cur->node;
+
+	BUG_ON(size > cur->remaining);
+
+	cur->remaining -= size;
+	if (!cur->remaining)
+		return;
+
+	cur->size -= size;
+	if (cur->size) {
+		cur->start += size;
+		return;
+	}
+
+	cur->node = ++node;
+	cur->start = node->start << PAGE_SHIFT;
+	cur->size = min(node->size << PAGE_SHIFT, cur->remaining);
+}
+
+#endif