1/*
2 * rtc class driver for the Maxim MAX6900 chip
3 *
4 * Author: Dale Farnsworth <dale@farnsworth.org>
5 *
6 * based on previously existing rtc class drivers
7 *
8 * 2007 (c) MontaVista, Software, Inc.  This file is licensed under
9 * the terms of the GNU General Public License version 2.  This program
10 * is licensed "as is" without any warranty of any kind, whether express
11 * or implied.
12 */
13
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 * register indices
24 */
25#define MAX6900_REG_SC			0	/* seconds      00-59 */
26#define MAX6900_REG_MN			1	/* minutes      00-59 */
27#define MAX6900_REG_HR			2	/* hours        00-23 */
28#define MAX6900_REG_DT			3	/* day of month 00-31 */
29#define MAX6900_REG_MO			4	/* month        01-12 */
30#define MAX6900_REG_DW			5	/* day of week   1-7  */
31#define MAX6900_REG_YR			6	/* year         00-99 */
32#define MAX6900_REG_CT			7	/* control */
33						/* register 8 is undocumented */
34#define MAX6900_REG_CENTURY		9	/* century */
35#define MAX6900_REG_LEN			10
36
37#define MAX6900_BURST_LEN		8	/* can burst r/w first 8 regs */
38
39#define MAX6900_REG_CT_WP		(1 << 7)	/* Write Protect */
40
41/*
42 * register read/write commands
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	/* specification says 2.5 mS */
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,	/* write */
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,	/* write */
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,	/* write */
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,	/* write */
110		 .len = sizeof(i2c_burst_buf),
111		 .buf = i2c_burst_buf}
112	};
113	int rc;
114
115	/*
116	 * We have to make separate calls to i2c_transfer because of
117	 * the need to delay after each write to the chip.  Also,
118	 * we write the century byte first, since we set the write-protect
119	 * bit as part of the burst write.
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	/* set write protect */
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};
237
238static struct i2c_driver max6900_driver = {
239	.driver = {
240		   .name = "rtc-max6900",
241		   },
242	.probe = max6900_probe,
243	.id_table = max6900_id,
244};
245
246module_i2c_driver(max6900_driver);
247
248MODULE_DESCRIPTION("Maxim MAX6900 RTC driver");
249MODULE_AUTHOR("Dale Farnsworth <dale@farnsworth.org>");
250MODULE_LICENSE("GPL");
251MODULE_VERSION(DRV_VERSION);
252