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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * Copyright (C) 2020 Nicolas Saenz Julienne <[email protected]>
4 */
5
6#include <linux/crc32.h>
7#include <linux/io.h>
8#include <linux/module.h>
9#include <linux/nvmem-provider.h>
10#include <linux/of_reserved_mem.h>
11#include <linux/platform_device.h>
12#include <linux/slab.h>
13
14struct rmem {
15 struct device *dev;
16 struct nvmem_device *nvmem;
17 struct reserved_mem *mem;
18};
19
20struct rmem_match_data {
21 int (*checksum)(struct rmem *priv);
22};
23
24struct __packed rmem_eyeq5_header {
25 u32 magic;
26 u32 version;
27 u32 size;
28};
29
30#define RMEM_EYEQ5_MAGIC ((u32)0xDABBAD00)
31
32static int rmem_read(void *context, unsigned int offset,
33 void *val, size_t bytes)
34{
35 struct rmem *priv = context;
36 void *addr;
37
38 if ((phys_addr_t)offset + bytes > priv->mem->size)
39 return -EIO;
40
41 /*
42 * Only map the reserved memory at this point to avoid potential rogue
43 * kernel threads inadvertently modifying it. Based on the current
44 * uses-cases for this driver, the performance hit isn't a concern.
45 * Nor is likely to be, given the nature of the subsystem. Most nvmem
46 * devices operate over slow buses to begin with.
47 *
48 * An alternative would be setting the memory as RO, set_memory_ro(),
49 * but as of Dec 2020 this isn't possible on arm64.
50 */
51 addr = memremap(priv->mem->base, priv->mem->size, MEMREMAP_WB);
52 if (!addr) {
53 dev_err(priv->dev, "Failed to remap memory region\n");
54 return -ENOMEM;
55 }
56
57 memcpy(val, addr + offset, bytes);
58
59 memunmap(addr);
60
61 return 0;
62}
63
64static int rmem_eyeq5_checksum(struct rmem *priv)
65{
66 void *buf __free(kfree) = NULL;
67 struct rmem_eyeq5_header header;
68 u32 computed_crc, *target_crc;
69 size_t data_size;
70 int ret;
71
72 ret = rmem_read(priv, 0, &header, sizeof(header));
73 if (ret)
74 return ret;
75
76 if (header.magic != RMEM_EYEQ5_MAGIC)
77 return -EINVAL;
78
79 /*
80 * Avoid massive kmalloc() if header read is invalid;
81 * the check would be done by the next rmem_read() anyway.
82 */
83 if (header.size > priv->mem->size)
84 return -EINVAL;
85
86 /*
87 * 0 +-------------------+
88 * | Header (12 bytes) | \
89 * +-------------------+ |
90 * | | | data to be CRCed
91 * | ... | |
92 * | | /
93 * data_size +-------------------+
94 * | CRC (4 bytes) |
95 * header.size +-------------------+
96 */
97
98 buf = kmalloc(header.size, GFP_KERNEL);
99 if (!buf)
100 return -ENOMEM;
101
102 ret = rmem_read(priv, 0, buf, header.size);
103 if (ret)
104 return ret;
105
106 data_size = header.size - sizeof(*target_crc);
107 target_crc = buf + data_size;
108 computed_crc = crc32(U32_MAX, buf, data_size) ^ U32_MAX;
109
110 if (computed_crc == *target_crc)
111 return 0;
112
113 dev_err(priv->dev,
114 "checksum failed: computed %#x, expected %#x, header (%#x, %#x, %#x)\n",
115 computed_crc, *target_crc, header.magic, header.version, header.size);
116 return -EINVAL;
117}
118
119static int rmem_probe(struct platform_device *pdev)
120{
121 struct nvmem_config config = { };
122 struct device *dev = &pdev->dev;
123 const struct rmem_match_data *match_data = device_get_match_data(dev);
124 struct reserved_mem *mem;
125 struct rmem *priv;
126
127 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
128 if (!priv)
129 return -ENOMEM;
130 priv->dev = dev;
131
132 mem = of_reserved_mem_lookup(dev->of_node);
133 if (!mem) {
134 dev_err(dev, "Failed to lookup reserved memory\n");
135 return -EINVAL;
136 }
137 priv->mem = mem;
138
139 config.dev = dev;
140 config.priv = priv;
141 config.name = "rmem";
142 config.id = NVMEM_DEVID_AUTO;
143 config.size = mem->size;
144 config.reg_read = rmem_read;
145
146 if (match_data && match_data->checksum) {
147 int ret = match_data->checksum(priv);
148
149 if (ret)
150 return ret;
151 }
152
153 return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
154}
155
156static const struct rmem_match_data rmem_eyeq5_match_data = {
157 .checksum = rmem_eyeq5_checksum,
158};
159
160static const struct of_device_id rmem_match[] = {
161 { .compatible = "mobileye,eyeq5-bootloader-config", .data = &rmem_eyeq5_match_data },
162 { .compatible = "nvmem-rmem", },
163 { /* sentinel */ },
164};
165MODULE_DEVICE_TABLE(of, rmem_match);
166
167static struct platform_driver rmem_driver = {
168 .probe = rmem_probe,
169 .driver = {
170 .name = "rmem",
171 .of_match_table = rmem_match,
172 },
173};
174module_platform_driver(rmem_driver);
175
176MODULE_AUTHOR("Nicolas Saenz Julienne <[email protected]>");
177MODULE_DESCRIPTION("Reserved Memory Based nvmem Driver");
178MODULE_LICENSE("GPL");