1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * rtc class driver for the Maxim MAX6900 chip |
4 | * |
5 | * Copyright (c) 2007 MontaVista, Software, Inc. |
6 | * |
7 | * Author: Dale Farnsworth <dale@farnsworth.org> |
8 | * |
9 | * based on previously existing rtc class drivers |
10 | */ |
11 | |
12 | #include <linux/module.h> |
13 | #include <linux/i2c.h> |
14 | #include <linux/bcd.h> |
15 | #include <linux/rtc.h> |
16 | #include <linux/delay.h> |
17 | |
18 | /* |
19 | * register indices |
20 | */ |
21 | #define MAX6900_REG_SC 0 /* seconds 00-59 */ |
22 | #define MAX6900_REG_MN 1 /* minutes 00-59 */ |
23 | #define MAX6900_REG_HR 2 /* hours 00-23 */ |
24 | #define MAX6900_REG_DT 3 /* day of month 00-31 */ |
25 | #define MAX6900_REG_MO 4 /* month 01-12 */ |
26 | #define MAX6900_REG_DW 5 /* day of week 1-7 */ |
27 | #define MAX6900_REG_YR 6 /* year 00-99 */ |
28 | #define MAX6900_REG_CT 7 /* control */ |
29 | /* register 8 is undocumented */ |
30 | #define MAX6900_REG_CENTURY 9 /* century */ |
31 | #define MAX6900_REG_LEN 10 |
32 | |
33 | #define MAX6900_BURST_LEN 8 /* can burst r/w first 8 regs */ |
34 | |
35 | #define MAX6900_REG_CT_WP (1 << 7) /* Write Protect */ |
36 | |
37 | /* |
38 | * register read/write commands |
39 | */ |
40 | #define MAX6900_REG_CONTROL_WRITE 0x8e |
41 | #define MAX6900_REG_CENTURY_WRITE 0x92 |
42 | #define MAX6900_REG_CENTURY_READ 0x93 |
43 | #define MAX6900_REG_RESERVED_READ 0x96 |
44 | #define MAX6900_REG_BURST_WRITE 0xbe |
45 | #define MAX6900_REG_BURST_READ 0xbf |
46 | |
47 | #define MAX6900_IDLE_TIME_AFTER_WRITE 3 /* specification says 2.5 mS */ |
48 | |
49 | static struct i2c_driver max6900_driver; |
50 | |
51 | static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf) |
52 | { |
53 | u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ }; |
54 | u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ }; |
55 | struct i2c_msg msgs[4] = { |
56 | { |
57 | .addr = client->addr, |
58 | .flags = 0, /* write */ |
59 | .len = sizeof(reg_burst_read), |
60 | .buf = reg_burst_read} |
61 | , |
62 | { |
63 | .addr = client->addr, |
64 | .flags = I2C_M_RD, |
65 | .len = MAX6900_BURST_LEN, |
66 | .buf = buf} |
67 | , |
68 | { |
69 | .addr = client->addr, |
70 | .flags = 0, /* write */ |
71 | .len = sizeof(reg_century_read), |
72 | .buf = reg_century_read} |
73 | , |
74 | { |
75 | .addr = client->addr, |
76 | .flags = I2C_M_RD, |
77 | .len = sizeof(buf[MAX6900_REG_CENTURY]), |
78 | .buf = &buf[MAX6900_REG_CENTURY] |
79 | } |
80 | }; |
81 | int rc; |
82 | |
83 | rc = i2c_transfer(adap: client->adapter, msgs, ARRAY_SIZE(msgs)); |
84 | if (rc != ARRAY_SIZE(msgs)) { |
85 | dev_err(&client->dev, "%s: register read failed\n" , __func__); |
86 | return -EIO; |
87 | } |
88 | return 0; |
89 | } |
90 | |
91 | static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf) |
92 | { |
93 | u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE }; |
94 | struct i2c_msg century_msgs[1] = { |
95 | { |
96 | .addr = client->addr, |
97 | .flags = 0, /* write */ |
98 | .len = sizeof(i2c_century_buf), |
99 | .buf = i2c_century_buf} |
100 | }; |
101 | u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE }; |
102 | struct i2c_msg burst_msgs[1] = { |
103 | { |
104 | .addr = client->addr, |
105 | .flags = 0, /* write */ |
106 | .len = sizeof(i2c_burst_buf), |
107 | .buf = i2c_burst_buf} |
108 | }; |
109 | int rc; |
110 | |
111 | /* |
112 | * We have to make separate calls to i2c_transfer because of |
113 | * the need to delay after each write to the chip. Also, |
114 | * we write the century byte first, since we set the write-protect |
115 | * bit as part of the burst write. |
116 | */ |
117 | i2c_century_buf[1] = buf[MAX6900_REG_CENTURY]; |
118 | |
119 | rc = i2c_transfer(adap: client->adapter, msgs: century_msgs, |
120 | ARRAY_SIZE(century_msgs)); |
121 | if (rc != ARRAY_SIZE(century_msgs)) |
122 | goto write_failed; |
123 | |
124 | msleep(MAX6900_IDLE_TIME_AFTER_WRITE); |
125 | |
126 | memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN); |
127 | |
128 | rc = i2c_transfer(adap: client->adapter, msgs: burst_msgs, ARRAY_SIZE(burst_msgs)); |
129 | if (rc != ARRAY_SIZE(burst_msgs)) |
130 | goto write_failed; |
131 | msleep(MAX6900_IDLE_TIME_AFTER_WRITE); |
132 | |
133 | return 0; |
134 | |
135 | write_failed: |
136 | dev_err(&client->dev, "%s: register write failed\n" , __func__); |
137 | return -EIO; |
138 | } |
139 | |
140 | static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm) |
141 | { |
142 | struct i2c_client *client = to_i2c_client(dev); |
143 | int rc; |
144 | u8 regs[MAX6900_REG_LEN]; |
145 | |
146 | rc = max6900_i2c_read_regs(client, buf: regs); |
147 | if (rc < 0) |
148 | return rc; |
149 | |
150 | tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]); |
151 | tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]); |
152 | tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f); |
153 | tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]); |
154 | tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1; |
155 | tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) + |
156 | bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900; |
157 | tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]); |
158 | |
159 | return 0; |
160 | } |
161 | |
162 | static int max6900_i2c_clear_write_protect(struct i2c_client *client) |
163 | { |
164 | return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, value: 0); |
165 | } |
166 | |
167 | static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm) |
168 | { |
169 | struct i2c_client *client = to_i2c_client(dev); |
170 | u8 regs[MAX6900_REG_LEN]; |
171 | int rc; |
172 | |
173 | rc = max6900_i2c_clear_write_protect(client); |
174 | if (rc < 0) |
175 | return rc; |
176 | |
177 | regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec); |
178 | regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min); |
179 | regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour); |
180 | regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday); |
181 | regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1); |
182 | regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday); |
183 | regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100); |
184 | regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100); |
185 | /* set write protect */ |
186 | regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP; |
187 | |
188 | rc = max6900_i2c_write_regs(client, buf: regs); |
189 | if (rc < 0) |
190 | return rc; |
191 | |
192 | return 0; |
193 | } |
194 | |
195 | static const struct rtc_class_ops max6900_rtc_ops = { |
196 | .read_time = max6900_rtc_read_time, |
197 | .set_time = max6900_rtc_set_time, |
198 | }; |
199 | |
200 | static int max6900_probe(struct i2c_client *client) |
201 | { |
202 | struct rtc_device *rtc; |
203 | |
204 | if (!i2c_check_functionality(adap: client->adapter, I2C_FUNC_I2C)) |
205 | return -ENODEV; |
206 | |
207 | rtc = devm_rtc_device_register(dev: &client->dev, name: max6900_driver.driver.name, |
208 | ops: &max6900_rtc_ops, THIS_MODULE); |
209 | if (IS_ERR(ptr: rtc)) |
210 | return PTR_ERR(ptr: rtc); |
211 | |
212 | i2c_set_clientdata(client, data: rtc); |
213 | |
214 | return 0; |
215 | } |
216 | |
217 | static const struct i2c_device_id max6900_id[] = { |
218 | { "max6900" , 0 }, |
219 | { } |
220 | }; |
221 | MODULE_DEVICE_TABLE(i2c, max6900_id); |
222 | |
223 | static struct i2c_driver max6900_driver = { |
224 | .driver = { |
225 | .name = "rtc-max6900" , |
226 | }, |
227 | .probe = max6900_probe, |
228 | .id_table = max6900_id, |
229 | }; |
230 | |
231 | module_i2c_driver(max6900_driver); |
232 | |
233 | MODULE_DESCRIPTION("Maxim MAX6900 RTC driver" ); |
234 | MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>" ); |
235 | MODULE_LICENSE("GPL" ); |
236 | |