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