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1// SPDX-License-Identifier: GPL-2.0-only
2//
3// Copyright 2020 Google Inc
4// Copyright 2025 Linaro Ltd.
5//
6// NVMEM driver for Maxim MAX77759
7
8#include <linux/dev_printk.h>
9#include <linux/device.h>
10#include <linux/device/driver.h>
11#include <linux/err.h>
12#include <linux/mfd/max77759.h>
13#include <linux/mod_devicetable.h>
14#include <linux/module.h>
15#include <linux/nvmem-provider.h>
16#include <linux/overflow.h>
17#include <linux/platform_device.h>
18#include <linux/string.h>
19
20#define MAX77759_NVMEM_OPCODE_HEADER_LEN 3
21/*
22 * NVMEM commands have a three byte header (which becomes part of the command),
23 * so we need to subtract that.
24 */
25#define MAX77759_NVMEM_SIZE (MAX77759_MAXQ_OPCODE_MAXLENGTH \
26 - MAX77759_NVMEM_OPCODE_HEADER_LEN)
27
28struct max77759_nvmem {
29 struct device *dev;
30 struct max77759 *max77759;
31};
32
33static int max77759_nvmem_reg_read(void *priv, unsigned int offset,
34 void *val, size_t bytes)
35{
36 struct max77759_nvmem *nvmem = priv;
37 DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
38 MAX77759_NVMEM_OPCODE_HEADER_LEN);
39 DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
40 MAX77759_MAXQ_OPCODE_MAXLENGTH);
41 int ret;
42
43 cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_READ;
44 cmd->cmd[1] = offset;
45 cmd->cmd[2] = bytes;
46 rsp->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
47
48 ret = max77759_maxq_command(nvmem->max77759, cmd, rsp);
49 if (ret < 0)
50 return ret;
51
52 if (memcmp(cmd->cmd, rsp->rsp, MAX77759_NVMEM_OPCODE_HEADER_LEN)) {
53 dev_warn(nvmem->dev, "protocol error (read)\n");
54 return -EIO;
55 }
56
57 memcpy(val, &rsp->rsp[MAX77759_NVMEM_OPCODE_HEADER_LEN], bytes);
58
59 return 0;
60}
61
62static int max77759_nvmem_reg_write(void *priv, unsigned int offset,
63 void *val, size_t bytes)
64{
65 struct max77759_nvmem *nvmem = priv;
66 DEFINE_FLEX(struct max77759_maxq_command, cmd, cmd, length,
67 MAX77759_MAXQ_OPCODE_MAXLENGTH);
68 DEFINE_FLEX(struct max77759_maxq_response, rsp, rsp, length,
69 MAX77759_MAXQ_OPCODE_MAXLENGTH);
70 int ret;
71
72 cmd->cmd[0] = MAX77759_MAXQ_OPCODE_USER_SPACE_WRITE;
73 cmd->cmd[1] = offset;
74 cmd->cmd[2] = bytes;
75 memcpy(&cmd->cmd[MAX77759_NVMEM_OPCODE_HEADER_LEN], val, bytes);
76 cmd->length = bytes + MAX77759_NVMEM_OPCODE_HEADER_LEN;
77 rsp->length = cmd->length;
78
79 ret = max77759_maxq_command(nvmem->max77759, cmd, rsp);
80 if (ret < 0)
81 return ret;
82
83 if (memcmp(cmd->cmd, rsp->rsp, cmd->length)) {
84 dev_warn(nvmem->dev, "protocol error (write)\n");
85 return -EIO;
86 }
87
88 return 0;
89}
90
91static int max77759_nvmem_probe(struct platform_device *pdev)
92{
93 struct nvmem_config config = {
94 .dev = &pdev->dev,
95 .name = dev_name(&pdev->dev),
96 .id = NVMEM_DEVID_NONE,
97 .type = NVMEM_TYPE_EEPROM,
98 .ignore_wp = true,
99 .size = MAX77759_NVMEM_SIZE,
100 .word_size = sizeof(u8),
101 .stride = sizeof(u8),
102 .reg_read = max77759_nvmem_reg_read,
103 .reg_write = max77759_nvmem_reg_write,
104 };
105 struct max77759_nvmem *nvmem;
106
107 nvmem = devm_kzalloc(&pdev->dev, sizeof(*nvmem), GFP_KERNEL);
108 if (!nvmem)
109 return -ENOMEM;
110
111 nvmem->dev = &pdev->dev;
112 nvmem->max77759 = dev_get_drvdata(pdev->dev.parent);
113
114 config.priv = nvmem;
115
116 return PTR_ERR_OR_ZERO(devm_nvmem_register(config.dev, &config));
117}
118
119static const struct of_device_id max77759_nvmem_of_id[] = {
120 { .compatible = "maxim,max77759-nvmem", },
121 { }
122};
123MODULE_DEVICE_TABLE(of, max77759_nvmem_of_id);
124
125static const struct platform_device_id max77759_nvmem_platform_id[] = {
126 { "max77759-nvmem", },
127 { }
128};
129MODULE_DEVICE_TABLE(platform, max77759_nvmem_platform_id);
130
131static struct platform_driver max77759_nvmem_driver = {
132 .driver = {
133 .name = "max77759-nvmem",
134 .probe_type = PROBE_PREFER_ASYNCHRONOUS,
135 .of_match_table = max77759_nvmem_of_id,
136 },
137 .probe = max77759_nvmem_probe,
138 .id_table = max77759_nvmem_platform_id,
139};
140
141module_platform_driver(max77759_nvmem_driver);
142
143MODULE_AUTHOR("André Draszik <andre.draszik@linaro.org>");
144MODULE_DESCRIPTION("NVMEM driver for Maxim MAX77759");
145MODULE_LICENSE("GPL");