1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * ee1004 - driver for DDR4 SPD EEPROMs
4 *
5 * Copyright (C) 2017-2019 Jean Delvare
6 *
7 * Based on the at24 driver:
8 * Copyright (C) 2005-2007 David Brownell
9 * Copyright (C) 2008 Wolfram Sang, Pengutronix
10 */
11
12 #include <linux/mfd/qnap-mcu.h>
13 #include <linux/module.h>
14 #include <linux/nvmem-provider.h>
15 #include <linux/platform_device.h>
16 #include <linux/slab.h>
17
18 /* Determined by trial and error until read anomalies appeared */
19 #define QNAP_MCU_EEPROM_SIZE 256
20 #define QNAP_MCU_EEPROM_BLOCK_SIZE 32
21
qnap_mcu_eeprom_read_block(struct qnap_mcu * mcu,unsigned int offset,void * val,size_t bytes)22 static int qnap_mcu_eeprom_read_block(struct qnap_mcu *mcu, unsigned int offset,
23 void *val, size_t bytes)
24 {
25 const u8 cmd[] = { 0xf7, 0xa1, offset, bytes };
26 u8 *reply;
27 int ret = 0;
28
29 reply = kzalloc(bytes + sizeof(cmd), GFP_KERNEL);
30 if (!reply)
31 return -ENOMEM;
32
33 ret = qnap_mcu_exec(mcu, cmd, sizeof(cmd), reply, bytes + sizeof(cmd));
34 if (ret)
35 goto out;
36
37 /* First bytes must mirror the sent command */
38 if (memcmp(cmd, reply, sizeof(cmd))) {
39 ret = -EIO;
40 goto out;
41 }
42
43 memcpy(val, reply + sizeof(cmd), bytes);
44
45 out:
46 kfree(reply);
47 return ret;
48 }
49
qnap_mcu_eeprom_read(void * priv,unsigned int offset,void * val,size_t bytes)50 static int qnap_mcu_eeprom_read(void *priv, unsigned int offset, void *val, size_t bytes)
51 {
52 struct qnap_mcu *mcu = priv;
53 int pos = 0, ret;
54 u8 *buf = val;
55
56 if (unlikely(!bytes))
57 return 0;
58
59 while (bytes > 0) {
60 size_t to_read = (bytes > QNAP_MCU_EEPROM_BLOCK_SIZE) ?
61 QNAP_MCU_EEPROM_BLOCK_SIZE : bytes;
62
63 ret = qnap_mcu_eeprom_read_block(mcu, offset + pos, &buf[pos], to_read);
64 if (ret < 0)
65 return ret;
66
67 pos += to_read;
68 bytes -= to_read;
69 }
70
71 return 0;
72 }
73
qnap_mcu_eeprom_probe(struct platform_device * pdev)74 static int qnap_mcu_eeprom_probe(struct platform_device *pdev)
75 {
76 struct qnap_mcu *mcu = dev_get_drvdata(pdev->dev.parent);
77 struct nvmem_config nvcfg = {};
78 struct nvmem_device *ndev;
79
80 nvcfg.dev = &pdev->dev;
81 nvcfg.of_node = pdev->dev.parent->of_node;
82 nvcfg.name = dev_name(&pdev->dev);
83 nvcfg.id = NVMEM_DEVID_NONE;
84 nvcfg.owner = THIS_MODULE;
85 nvcfg.type = NVMEM_TYPE_EEPROM;
86 nvcfg.read_only = true;
87 nvcfg.root_only = false;
88 nvcfg.reg_read = qnap_mcu_eeprom_read;
89 nvcfg.size = QNAP_MCU_EEPROM_SIZE;
90 nvcfg.word_size = 1;
91 nvcfg.stride = 1;
92 nvcfg.priv = mcu;
93
94 ndev = devm_nvmem_register(&pdev->dev, &nvcfg);
95 if (IS_ERR(ndev))
96 return PTR_ERR(ndev);
97
98 return 0;
99 }
100
101 static struct platform_driver qnap_mcu_eeprom_driver = {
102 .probe = qnap_mcu_eeprom_probe,
103 .driver = {
104 .name = "qnap-mcu-eeprom",
105 },
106 };
107 module_platform_driver(qnap_mcu_eeprom_driver);
108
109 MODULE_AUTHOR("Heiko Stuebner <heiko@sntech.de>");
110 MODULE_DESCRIPTION("QNAP MCU EEPROM driver");
111 MODULE_LICENSE("GPL");
112