1 /* SPDX-License-Identifier: GPL-2.0 OR MIT 2 * 3 * Copyright 2026 Advanced Micro Devices, Inc. 4 * 5 * Permission is hereby granted, free of charge, to any person obtaining a 6 * copy of this software and associated documentation files (the "Software"), 7 * to deal in the Software without restriction, including without limitation 8 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 9 * and/or sell copies of the Software, and to permit persons to whom the 10 * Software is furnished to do so, subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be included in 13 * all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 18 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR 19 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 20 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 21 * OTHER DEALINGS IN THE SOFTWARE. 22 */ 23 #ifndef __AMDGPU_WB_H__ 24 #define __AMDGPU_WB_H__ 25 26 #include <linux/types.h> 27 #include <linux/spinlock_types.h> 28 #include <linux/math.h> 29 30 /* 31 * Writeback 32 */ 33 #define AMDGPU_MAX_WB 1024 /* Reserve at most 1024 WB slots for amdgpu-owned rings. */ 34 35 /** 36 * struct amdgpu_wb - This struct is used for small GPU memory allocation. 37 * 38 * This struct is used to allocate a small amount of GPU memory that can be 39 * used to shadow certain states into the memory. This is especially useful for 40 * providing easy CPU access to some states without requiring register access 41 * (e.g., if some block is power gated, reading register may be problematic). 42 * 43 * Note: the term writeback was initially used because many of the amdgpu 44 * components had some level of writeback memory, and this struct initially 45 * described those components. 46 */ 47 48 struct amdgpu_bo; 49 struct amdgpu_device; 50 51 struct amdgpu_wb { 52 53 /** 54 * @wb_obj: 55 * 56 * Buffer Object used for the writeback memory. 57 */ 58 struct amdgpu_bo *wb_obj; 59 60 /** 61 * @wb: 62 * 63 * Pointer to the first writeback slot. In terms of CPU address 64 * this value can be accessed directly by using the offset as an index. 65 * For the GPU address, it is necessary to use gpu_addr and the offset. 66 */ 67 uint32_t *wb; 68 69 /** 70 * @gpu_addr: 71 * 72 * Writeback base address in the GPU. 73 */ 74 uint64_t gpu_addr; 75 76 /** 77 * @num_wb: 78 * 79 * Number of writeback slots reserved for amdgpu. 80 */ 81 u32 num_wb; 82 83 /** 84 * @used: 85 * 86 * Track the writeback slot already used. 87 */ 88 unsigned long used[DIV_ROUND_UP(AMDGPU_MAX_WB, BITS_PER_LONG)]; 89 90 /** 91 * @lock: 92 * 93 * Protects read and write of the used field array. 94 */ 95 spinlock_t lock; 96 }; 97 98 void amdgpu_wb_fini(struct amdgpu_device *adev); 99 int amdgpu_wb_init(struct amdgpu_device *adev); 100 int amdgpu_wb_get(struct amdgpu_device *adev, u32 *wb); 101 void amdgpu_wb_free(struct amdgpu_device *adev, u32 wb); 102 #endif 103