tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * RISC-V specific functions to support DMA for non-coherent devices
4 *
5 * Copyright (c) 2021 Western Digital Corporation or its affiliates.
6 */
7
8#include <linux/dma-direct.h>
9#include <linux/dma-map-ops.h>
10#include <linux/mm.h>
11#include <asm/cacheflush.h>
12#include <asm/dma-noncoherent.h>
13
14static bool noncoherent_supported __ro_after_init;
15int dma_cache_alignment __ro_after_init = ARCH_DMA_MINALIGN;
16EXPORT_SYMBOL_GPL(dma_cache_alignment);
17
18static inline void arch_dma_cache_wback(phys_addr_t paddr, size_t size)
19{
20 void *vaddr = phys_to_virt(paddr);
21
22#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
23 if (unlikely(noncoherent_cache_ops.wback)) {
24 noncoherent_cache_ops.wback(paddr, size);
25 return;
26 }
27#endif
28 ALT_CMO_OP(CLEAN, vaddr, size, riscv_cbom_block_size);
29}
30
31static inline void arch_dma_cache_inv(phys_addr_t paddr, size_t size)
32{
33 void *vaddr = phys_to_virt(paddr);
34
35#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
36 if (unlikely(noncoherent_cache_ops.inv)) {
37 noncoherent_cache_ops.inv(paddr, size);
38 return;
39 }
40#endif
41
42 ALT_CMO_OP(INVAL, vaddr, size, riscv_cbom_block_size);
43}
44
45static inline void arch_dma_cache_wback_inv(phys_addr_t paddr, size_t size)
46{
47 void *vaddr = phys_to_virt(paddr);
48
49#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
50 if (unlikely(noncoherent_cache_ops.wback_inv)) {
51 noncoherent_cache_ops.wback_inv(paddr, size);
52 return;
53 }
54#endif
55
56 ALT_CMO_OP(FLUSH, vaddr, size, riscv_cbom_block_size);
57}
58
59static inline bool arch_sync_dma_clean_before_fromdevice(void)
60{
61 return true;
62}
63
64static inline bool arch_sync_dma_cpu_needs_post_dma_flush(void)
65{
66 return true;
67}
68
69void arch_sync_dma_for_device(phys_addr_t paddr, size_t size,
70 enum dma_data_direction dir)
71{
72 switch (dir) {
73 case DMA_TO_DEVICE:
74 arch_dma_cache_wback(paddr, size);
75 break;
76
77 case DMA_FROM_DEVICE:
78 if (!arch_sync_dma_clean_before_fromdevice()) {
79 arch_dma_cache_inv(paddr, size);
80 break;
81 }
82 fallthrough;
83
84 case DMA_BIDIRECTIONAL:
85 /* Skip the invalidate here if it's done later */
86 if (IS_ENABLED(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) &&
87 arch_sync_dma_cpu_needs_post_dma_flush())
88 arch_dma_cache_wback(paddr, size);
89 else
90 arch_dma_cache_wback_inv(paddr, size);
91 break;
92
93 default:
94 break;
95 }
96}
97
98void arch_sync_dma_for_cpu(phys_addr_t paddr, size_t size,
99 enum dma_data_direction dir)
100{
101 switch (dir) {
102 case DMA_TO_DEVICE:
103 break;
104
105 case DMA_FROM_DEVICE:
106 case DMA_BIDIRECTIONAL:
107 /* FROM_DEVICE invalidate needed if speculative CPU prefetch only */
108 if (arch_sync_dma_cpu_needs_post_dma_flush())
109 arch_dma_cache_inv(paddr, size);
110 break;
111
112 default:
113 break;
114 }
115}
116
117void arch_dma_prep_coherent(struct page *page, size_t size)
118{
119 void *flush_addr = page_address(page);
120
121#ifdef CONFIG_RISCV_NONSTANDARD_CACHE_OPS
122 if (unlikely(noncoherent_cache_ops.wback_inv)) {
123 noncoherent_cache_ops.wback_inv(page_to_phys(page), size);
124 return;
125 }
126#endif
127
128 ALT_CMO_OP(FLUSH, flush_addr, size, riscv_cbom_block_size);
129}
130
131void arch_setup_dma_ops(struct device *dev, bool coherent)
132{
133 WARN_TAINT(!coherent && riscv_cbom_block_size > ARCH_DMA_MINALIGN,
134 TAINT_CPU_OUT_OF_SPEC,
135 "%s %s: ARCH_DMA_MINALIGN smaller than riscv,cbom-block-size (%d < %d)",
136 dev_driver_string(dev), dev_name(dev),
137 ARCH_DMA_MINALIGN, riscv_cbom_block_size);
138
139 WARN_TAINT(!coherent && !noncoherent_supported, TAINT_CPU_OUT_OF_SPEC,
140 "%s %s: device non-coherent but no non-coherent operations supported",
141 dev_driver_string(dev), dev_name(dev));
142
143 dev->dma_coherent = coherent;
144}
145
146void riscv_noncoherent_supported(void)
147{
148 WARN(!riscv_cbom_block_size,
149 "Non-coherent DMA support enabled without a block size\n");
150 noncoherent_supported = true;
151}
152
153void __init riscv_set_dma_cache_alignment(void)
154{
155 if (!noncoherent_supported)
156 dma_cache_alignment = 1;
157}