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14#include <linux/module.h>
15#include <linux/i2c.h>
16#include <linux/bcd.h>
17#include <linux/rtc.h>
18#include <linux/delay.h>
19
20#define DRV_VERSION "0.2"
21
22
23
24
25#define MAX6900_REG_SC 0
26#define MAX6900_REG_MN 1
27#define MAX6900_REG_HR 2
28#define MAX6900_REG_DT 3
29#define MAX6900_REG_MO 4
30#define MAX6900_REG_DW 5
31#define MAX6900_REG_YR 6
32#define MAX6900_REG_CT 7
33
34#define MAX6900_REG_CENTURY 9
35#define MAX6900_REG_LEN 10
36
37#define MAX6900_BURST_LEN 8
38
39#define MAX6900_REG_CT_WP (1 << 7)
40
41
42
43
44#define MAX6900_REG_CONTROL_WRITE 0x8e
45#define MAX6900_REG_CENTURY_WRITE 0x92
46#define MAX6900_REG_CENTURY_READ 0x93
47#define MAX6900_REG_RESERVED_READ 0x96
48#define MAX6900_REG_BURST_WRITE 0xbe
49#define MAX6900_REG_BURST_READ 0xbf
50
51#define MAX6900_IDLE_TIME_AFTER_WRITE 3
52
53static struct i2c_driver max6900_driver;
54
55static int max6900_i2c_read_regs(struct i2c_client *client, u8 *buf)
56{
57 u8 reg_burst_read[1] = { MAX6900_REG_BURST_READ };
58 u8 reg_century_read[1] = { MAX6900_REG_CENTURY_READ };
59 struct i2c_msg msgs[4] = {
60 {
61 .addr = client->addr,
62 .flags = 0,
63 .len = sizeof(reg_burst_read),
64 .buf = reg_burst_read}
65 ,
66 {
67 .addr = client->addr,
68 .flags = I2C_M_RD,
69 .len = MAX6900_BURST_LEN,
70 .buf = buf}
71 ,
72 {
73 .addr = client->addr,
74 .flags = 0,
75 .len = sizeof(reg_century_read),
76 .buf = reg_century_read}
77 ,
78 {
79 .addr = client->addr,
80 .flags = I2C_M_RD,
81 .len = sizeof(buf[MAX6900_REG_CENTURY]),
82 .buf = &buf[MAX6900_REG_CENTURY]
83 }
84 };
85 int rc;
86
87 rc = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
88 if (rc != ARRAY_SIZE(msgs)) {
89 dev_err(&client->dev, "%s: register read failed\n", __func__);
90 return -EIO;
91 }
92 return 0;
93}
94
95static int max6900_i2c_write_regs(struct i2c_client *client, u8 const *buf)
96{
97 u8 i2c_century_buf[1 + 1] = { MAX6900_REG_CENTURY_WRITE };
98 struct i2c_msg century_msgs[1] = {
99 {
100 .addr = client->addr,
101 .flags = 0,
102 .len = sizeof(i2c_century_buf),
103 .buf = i2c_century_buf}
104 };
105 u8 i2c_burst_buf[MAX6900_BURST_LEN + 1] = { MAX6900_REG_BURST_WRITE };
106 struct i2c_msg burst_msgs[1] = {
107 {
108 .addr = client->addr,
109 .flags = 0,
110 .len = sizeof(i2c_burst_buf),
111 .buf = i2c_burst_buf}
112 };
113 int rc;
114
115
116
117
118
119
120
121 i2c_century_buf[1] = buf[MAX6900_REG_CENTURY];
122
123 rc = i2c_transfer(client->adapter, century_msgs,
124 ARRAY_SIZE(century_msgs));
125 if (rc != ARRAY_SIZE(century_msgs))
126 goto write_failed;
127
128 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
129
130 memcpy(&i2c_burst_buf[1], buf, MAX6900_BURST_LEN);
131
132 rc = i2c_transfer(client->adapter, burst_msgs, ARRAY_SIZE(burst_msgs));
133 if (rc != ARRAY_SIZE(burst_msgs))
134 goto write_failed;
135 msleep(MAX6900_IDLE_TIME_AFTER_WRITE);
136
137 return 0;
138
139 write_failed:
140 dev_err(&client->dev, "%s: register write failed\n", __func__);
141 return -EIO;
142}
143
144static int max6900_i2c_read_time(struct i2c_client *client, struct rtc_time *tm)
145{
146 int rc;
147 u8 regs[MAX6900_REG_LEN];
148
149 rc = max6900_i2c_read_regs(client, regs);
150 if (rc < 0)
151 return rc;
152
153 tm->tm_sec = bcd2bin(regs[MAX6900_REG_SC]);
154 tm->tm_min = bcd2bin(regs[MAX6900_REG_MN]);
155 tm->tm_hour = bcd2bin(regs[MAX6900_REG_HR] & 0x3f);
156 tm->tm_mday = bcd2bin(regs[MAX6900_REG_DT]);
157 tm->tm_mon = bcd2bin(regs[MAX6900_REG_MO]) - 1;
158 tm->tm_year = bcd2bin(regs[MAX6900_REG_YR]) +
159 bcd2bin(regs[MAX6900_REG_CENTURY]) * 100 - 1900;
160 tm->tm_wday = bcd2bin(regs[MAX6900_REG_DW]);
161
162 return rtc_valid_tm(tm);
163}
164
165static int max6900_i2c_clear_write_protect(struct i2c_client *client)
166{
167 return i2c_smbus_write_byte_data(client, MAX6900_REG_CONTROL_WRITE, 0);
168}
169
170static int
171max6900_i2c_set_time(struct i2c_client *client, struct rtc_time const *tm)
172{
173 u8 regs[MAX6900_REG_LEN];
174 int rc;
175
176 rc = max6900_i2c_clear_write_protect(client);
177 if (rc < 0)
178 return rc;
179
180 regs[MAX6900_REG_SC] = bin2bcd(tm->tm_sec);
181 regs[MAX6900_REG_MN] = bin2bcd(tm->tm_min);
182 regs[MAX6900_REG_HR] = bin2bcd(tm->tm_hour);
183 regs[MAX6900_REG_DT] = bin2bcd(tm->tm_mday);
184 regs[MAX6900_REG_MO] = bin2bcd(tm->tm_mon + 1);
185 regs[MAX6900_REG_DW] = bin2bcd(tm->tm_wday);
186 regs[MAX6900_REG_YR] = bin2bcd(tm->tm_year % 100);
187 regs[MAX6900_REG_CENTURY] = bin2bcd((tm->tm_year + 1900) / 100);
188
189 regs[MAX6900_REG_CT] = MAX6900_REG_CT_WP;
190
191 rc = max6900_i2c_write_regs(client, regs);
192 if (rc < 0)
193 return rc;
194
195 return 0;
196}
197
198static int max6900_rtc_read_time(struct device *dev, struct rtc_time *tm)
199{
200 return max6900_i2c_read_time(to_i2c_client(dev), tm);
201}
202
203static int max6900_rtc_set_time(struct device *dev, struct rtc_time *tm)
204{
205 return max6900_i2c_set_time(to_i2c_client(dev), tm);
206}
207
208static const struct rtc_class_ops max6900_rtc_ops = {
209 .read_time = max6900_rtc_read_time,
210 .set_time = max6900_rtc_set_time,
211};
212
213static int
214max6900_probe(struct i2c_client *client, const struct i2c_device_id *id)
215{
216 struct rtc_device *rtc;
217
218 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
219 return -ENODEV;
220
221 dev_info(&client->dev, "chip found, driver version " DRV_VERSION "\n");
222
223 rtc = devm_rtc_device_register(&client->dev, max6900_driver.driver.name,
224 &max6900_rtc_ops, THIS_MODULE);
225 if (IS_ERR(rtc))
226 return PTR_ERR(rtc);
227
228 i2c_set_clientdata(client, rtc);
229
230 return 0;
231}
232
233static struct i2c_device_id max6900_id[] = {
234 { "max6900", 0 },
235 { }
236};
237MODULE_DEVICE_TABLE(i2c, max6900_id);
238
239static struct i2c_driver max6900_driver = {
240 .driver = {
241 .name = "rtc-max6900",
242 },
243 .probe = max6900_probe,
244 .id_table = max6900_id,
245};
246
247module_i2c_driver(max6900_driver);
248
249MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
250MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
251MODULE_LICENSE("GPL");
252MODULE_VERSION(DRV_VERSION);
253
