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1/* SPDX-License-Identifier: GPL-2.0-or-later */
2#ifndef __LINUX_CMA_H
3#define __LINUX_CMA_H
4
5/*
6 * Contiguous Memory Allocator for DMA mapping framework
7 * Copyright (c) 2010-2011 by Samsung Electronics.
8 * Written by:
9 * Marek Szyprowski <m.szyprowski@samsung.com>
10 * Michal Nazarewicz <mina86@mina86.com>
11 */
12
13/*
14 * Contiguous Memory Allocator
15 *
16 * The Contiguous Memory Allocator (CMA) makes it possible to
17 * allocate big contiguous chunks of memory after the system has
18 * booted.
19 *
20 * Why is it needed?
21 *
22 * Various devices on embedded systems have no scatter-getter and/or
23 * IO map support and require contiguous blocks of memory to
24 * operate. They include devices such as cameras, hardware video
25 * coders, etc.
26 *
27 * Such devices often require big memory buffers (a full HD frame
28 * is, for instance, more then 2 mega pixels large, i.e. more than 6
29 * MB of memory), which makes mechanisms such as kmalloc() or
30 * alloc_page() ineffective.
31 *
32 * At the same time, a solution where a big memory region is
33 * reserved for a device is suboptimal since often more memory is
34 * reserved then strictly required and, moreover, the memory is
35 * inaccessible to page system even if device drivers don't use it.
36 *
37 * CMA tries to solve this issue by operating on memory regions
38 * where only movable pages can be allocated from. This way, kernel
39 * can use the memory for pagecache and when device driver requests
40 * it, allocated pages can be migrated.
41 *
42 * Driver usage
43 *
44 * CMA should not be used by the device drivers directly. It is
45 * only a helper framework for dma-mapping subsystem.
46 *
47 * For more information, see kernel-docs in kernel/dma/contiguous.c
48 */
49
50#ifdef __KERNEL__
51
52#include <linux/device.h>
53#include <linux/mm.h>
54
55struct cma;
56struct page;
57
58#ifdef CONFIG_DMA_CMA
59
60extern struct cma *dma_contiguous_default_area;
61
62static inline struct cma *dev_get_cma_area(struct device *dev)
63{
64 if (dev && dev->cma_area)
65 return dev->cma_area;
66 return dma_contiguous_default_area;
67}
68
69static inline void dev_set_cma_area(struct device *dev, struct cma *cma)
70{
71 if (dev)
72 dev->cma_area = cma;
73}
74
75static inline void dma_contiguous_set_default(struct cma *cma)
76{
77 dma_contiguous_default_area = cma;
78}
79
80void dma_contiguous_reserve(phys_addr_t addr_limit);
81
82int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
83 phys_addr_t limit, struct cma **res_cma,
84 bool fixed);
85
86/**
87 * dma_declare_contiguous() - reserve area for contiguous memory handling
88 * for particular device
89 * @dev: Pointer to device structure.
90 * @size: Size of the reserved memory.
91 * @base: Start address of the reserved memory (optional, 0 for any).
92 * @limit: End address of the reserved memory (optional, 0 for any).
93 *
94 * This function reserves memory for specified device. It should be
95 * called by board specific code when early allocator (memblock or bootmem)
96 * is still activate.
97 */
98
99static inline int dma_declare_contiguous(struct device *dev, phys_addr_t size,
100 phys_addr_t base, phys_addr_t limit)
101{
102 struct cma *cma;
103 int ret;
104 ret = dma_contiguous_reserve_area(size, base, limit, &cma, true);
105 if (ret == 0)
106 dev_set_cma_area(dev, cma);
107
108 return ret;
109}
110
111struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
112 unsigned int order, bool no_warn);
113bool dma_release_from_contiguous(struct device *dev, struct page *pages,
114 int count);
115struct page *dma_alloc_contiguous(struct device *dev, size_t size, gfp_t gfp);
116void dma_free_contiguous(struct device *dev, struct page *page, size_t size);
117
118#else
119
120static inline struct cma *dev_get_cma_area(struct device *dev)
121{
122 return NULL;
123}
124
125static inline void dev_set_cma_area(struct device *dev, struct cma *cma) { }
126
127static inline void dma_contiguous_set_default(struct cma *cma) { }
128
129static inline void dma_contiguous_reserve(phys_addr_t limit) { }
130
131static inline int dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
132 phys_addr_t limit, struct cma **res_cma,
133 bool fixed)
134{
135 return -ENOSYS;
136}
137
138static inline
139int dma_declare_contiguous(struct device *dev, phys_addr_t size,
140 phys_addr_t base, phys_addr_t limit)
141{
142 return -ENOSYS;
143}
144
145static inline
146struct page *dma_alloc_from_contiguous(struct device *dev, size_t count,
147 unsigned int order, bool no_warn)
148{
149 return NULL;
150}
151
152static inline
153bool dma_release_from_contiguous(struct device *dev, struct page *pages,
154 int count)
155{
156 return false;
157}
158
159/* Use fallback alloc() and free() when CONFIG_DMA_CMA=n */
160static inline struct page *dma_alloc_contiguous(struct device *dev, size_t size,
161 gfp_t gfp)
162{
163 return NULL;
164}
165
166static inline void dma_free_contiguous(struct device *dev, struct page *page,
167 size_t size)
168{
169 __free_pages(page, get_order(size));
170}
171
172#endif
173
174#endif
175
176#endif