1/*
2 * Driver for TI BQ32000 RTC.
3 *
4 * Copyright (C) 2009 Semihalf.
5 * Copyright (C) 2014 Pavel Machek <pavel@denx.de>
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * You can get hardware description at
12 * http://www.ti.com/lit/ds/symlink/bq32000.pdf
13 */
14
15#include <linux/module.h>
16#include <linux/i2c.h>
17#include <linux/rtc.h>
18#include <linux/init.h>
19#include <linux/errno.h>
20#include <linux/bcd.h>
21
22#define BQ32K_SECONDS		0x00	/* Seconds register address */
23#define BQ32K_SECONDS_MASK	0x7F	/* Mask over seconds value */
24#define BQ32K_STOP		0x80	/* Oscillator Stop flat */
25
26#define BQ32K_MINUTES		0x01	/* Minutes register address */
27#define BQ32K_MINUTES_MASK	0x7F	/* Mask over minutes value */
28#define BQ32K_OF		0x80	/* Oscillator Failure flag */
29
30#define BQ32K_HOURS_MASK	0x3F	/* Mask over hours value */
31#define BQ32K_CENT		0x40	/* Century flag */
32#define BQ32K_CENT_EN		0x80	/* Century flag enable bit */
33
34#define BQ32K_CALIBRATION	0x07	/* CAL_CFG1, calibration and control */
35#define BQ32K_TCH2		0x08	/* Trickle charge enable */
36#define BQ32K_CFG2		0x09	/* Trickle charger control */
37
38struct bq32k_regs {
39	uint8_t		seconds;
40	uint8_t		minutes;
41	uint8_t		cent_hours;
42	uint8_t		day;
43	uint8_t		date;
44	uint8_t		month;
45	uint8_t		years;
46};
47
48static struct i2c_driver bq32k_driver;
49
50static int bq32k_read(struct device *dev, void *data, uint8_t off, uint8_t len)
51{
52	struct i2c_client *client = to_i2c_client(dev);
53	struct i2c_msg msgs[] = {
54		{
55			.addr = client->addr,
56			.flags = 0,
57			.len = 1,
58			.buf = &off,
59		}, {
60			.addr = client->addr,
61			.flags = I2C_M_RD,
62			.len = len,
63			.buf = data,
64		}
65	};
66
67	if (i2c_transfer(client->adapter, msgs, 2) == 2)
68		return 0;
69
70	return -EIO;
71}
72
73static int bq32k_write(struct device *dev, void *data, uint8_t off, uint8_t len)
74{
75	struct i2c_client *client = to_i2c_client(dev);
76	uint8_t buffer[len + 1];
77
78	buffer[0] = off;
79	memcpy(&buffer[1], data, len);
80
81	if (i2c_master_send(client, buffer, len + 1) == len + 1)
82		return 0;
83
84	return -EIO;
85}
86
87static int bq32k_rtc_read_time(struct device *dev, struct rtc_time *tm)
88{
89	struct bq32k_regs regs;
90	int error;
91
92	error = bq32k_read(dev, &regs, 0, sizeof(regs));
93	if (error)
94		return error;
95
96	tm->tm_sec = bcd2bin(regs.seconds & BQ32K_SECONDS_MASK);
97	tm->tm_min = bcd2bin(regs.minutes & BQ32K_SECONDS_MASK);
98	tm->tm_hour = bcd2bin(regs.cent_hours & BQ32K_HOURS_MASK);
99	tm->tm_mday = bcd2bin(regs.date);
100	tm->tm_wday = bcd2bin(regs.day) - 1;
101	tm->tm_mon = bcd2bin(regs.month) - 1;
102	tm->tm_year = bcd2bin(regs.years) +
103				((regs.cent_hours & BQ32K_CENT) ? 100 : 0);
104
105	return rtc_valid_tm(tm);
106}
107
108static int bq32k_rtc_set_time(struct device *dev, struct rtc_time *tm)
109{
110	struct bq32k_regs regs;
111
112	regs.seconds = bin2bcd(tm->tm_sec);
113	regs.minutes = bin2bcd(tm->tm_min);
114	regs.cent_hours = bin2bcd(tm->tm_hour) | BQ32K_CENT_EN;
115	regs.day = bin2bcd(tm->tm_wday + 1);
116	regs.date = bin2bcd(tm->tm_mday);
117	regs.month = bin2bcd(tm->tm_mon + 1);
118
119	if (tm->tm_year >= 100) {
120		regs.cent_hours |= BQ32K_CENT;
121		regs.years = bin2bcd(tm->tm_year - 100);
122	} else
123		regs.years = bin2bcd(tm->tm_year);
124
125	return bq32k_write(dev, &regs, 0, sizeof(regs));
126}
127
128static const struct rtc_class_ops bq32k_rtc_ops = {
129	.read_time	= bq32k_rtc_read_time,
130	.set_time	= bq32k_rtc_set_time,
131};
132
133static int trickle_charger_of_init(struct device *dev, struct device_node *node)
134{
135	unsigned char reg;
136	int error;
137	u32 ohms = 0;
138
139	if (of_property_read_u32(node, "trickle-resistor-ohms" , &ohms))
140		return 0;
141
142	switch (ohms) {
143	case 180+940:
144		/*
145		 * TCHE[3:0] == 0x05, TCH2 == 1, TCFE == 0 (charging
146		 * over diode and 940ohm resistor)
147		 */
148
149		if (of_property_read_bool(node, "trickle-diode-disable")) {
150			dev_err(dev, "diode and resistor mismatch\n");
151			return -EINVAL;
152		}
153		reg = 0x05;
154		break;
155
156	case 180+20000:
157		/* diode disabled */
158
159		if (!of_property_read_bool(node, "trickle-diode-disable")) {
160			dev_err(dev, "bq32k: diode and resistor mismatch\n");
161			return -EINVAL;
162		}
163		reg = 0x45;
164		break;
165
166	default:
167		dev_err(dev, "invalid resistor value (%d)\n", ohms);
168		return -EINVAL;
169	}
170
171	error = bq32k_write(dev, &reg, BQ32K_CFG2, 1);
172	if (error)
173		return error;
174
175	reg = 0x20;
176	error = bq32k_write(dev, &reg, BQ32K_TCH2, 1);
177	if (error)
178		return error;
179
180	dev_info(dev, "Enabled trickle RTC battery charge.\n");
181	return 0;
182}
183
184static int bq32k_probe(struct i2c_client *client,
185				const struct i2c_device_id *id)
186{
187	struct device *dev = &client->dev;
188	struct rtc_device *rtc;
189	uint8_t reg;
190	int error;
191
192	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
193		return -ENODEV;
194
195	/* Check Oscillator Stop flag */
196	error = bq32k_read(dev, &reg, BQ32K_SECONDS, 1);
197	if (!error && (reg & BQ32K_STOP)) {
198		dev_warn(dev, "Oscillator was halted. Restarting...\n");
199		reg &= ~BQ32K_STOP;
200		error = bq32k_write(dev, &reg, BQ32K_SECONDS, 1);
201	}
202	if (error)
203		return error;
204
205	/* Check Oscillator Failure flag */
206	error = bq32k_read(dev, &reg, BQ32K_MINUTES, 1);
207	if (!error && (reg & BQ32K_OF)) {
208		dev_warn(dev, "Oscillator Failure. Check RTC battery.\n");
209		reg &= ~BQ32K_OF;
210		error = bq32k_write(dev, &reg, BQ32K_MINUTES, 1);
211	}
212	if (error)
213		return error;
214
215	if (client && client->dev.of_node)
216		trickle_charger_of_init(dev, client->dev.of_node);
217
218	rtc = devm_rtc_device_register(&client->dev, bq32k_driver.driver.name,
219						&bq32k_rtc_ops, THIS_MODULE);
220	if (IS_ERR(rtc))
221		return PTR_ERR(rtc);
222
223	i2c_set_clientdata(client, rtc);
224
225	return 0;
226}
227
228static const struct i2c_device_id bq32k_id[] = {
229	{ "bq32000", 0 },
230	{ }
231};
232MODULE_DEVICE_TABLE(i2c, bq32k_id);
233
234static struct i2c_driver bq32k_driver = {
235	.driver = {
236		.name	= "bq32k",
237		.owner	= THIS_MODULE,
238	},
239	.probe		= bq32k_probe,
240	.id_table	= bq32k_id,
241};
242
243module_i2c_driver(bq32k_driver);
244
245MODULE_AUTHOR("Semihalf, Piotr Ziecik <kosmo@semihalf.com>");
246MODULE_DESCRIPTION("TI BQ32000 I2C RTC driver");
247MODULE_LICENSE("GPL");
248