1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) 2012 Avionic Design GmbH
  4 */
  5
  6#include <linux/bcd.h>
  7#include <linux/i2c.h>
  8#include <linux/module.h>
  9#include <linux/rtc.h>
 10#include <linux/of.h>
 11
 12#define DRIVER_NAME "rtc-pcf8523"
 13
 14#define REG_CONTROL1 0x00
 15#define REG_CONTROL1_CAP_SEL (1 << 7)
 16#define REG_CONTROL1_STOP    (1 << 5)
 17
 18#define REG_CONTROL3 0x02
 19#define REG_CONTROL3_PM_BLD (1 << 7) /* battery low detection disabled */
 20#define REG_CONTROL3_PM_VDD (1 << 6) /* switch-over disabled */
 21#define REG_CONTROL3_PM_DSM (1 << 5) /* direct switching mode */
 22#define REG_CONTROL3_PM_MASK 0xe0
 23#define REG_CONTROL3_BLF (1 << 2) /* battery low bit, read-only */
 24
 25#define REG_SECONDS  0x03
 26#define REG_SECONDS_OS (1 << 7)
 27
 28#define REG_MINUTES  0x04
 29#define REG_HOURS    0x05
 30#define REG_DAYS     0x06
 31#define REG_WEEKDAYS 0x07
 32#define REG_MONTHS   0x08
 33#define REG_YEARS    0x09
 34
 35#define REG_OFFSET   0x0e
 36#define REG_OFFSET_MODE BIT(7)
 37
 38static int pcf8523_read(struct i2c_client *client, u8 reg, u8 *valuep)
 39{
 40	struct i2c_msg msgs[2];
 41	u8 value = 0;
 42	int err;
 43
 44	msgs[0].addr = client->addr;
 45	msgs[0].flags = 0;
 46	msgs[0].len = sizeof(reg);
 47	msgs[0].buf = &reg;
 48
 49	msgs[1].addr = client->addr;
 50	msgs[1].flags = I2C_M_RD;
 51	msgs[1].len = sizeof(value);
 52	msgs[1].buf = &value;
 53
 54	err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
 55	if (err < 0)
 56		return err;
 57
 58	*valuep = value;
 59
 60	return 0;
 61}
 62
 63static int pcf8523_write(struct i2c_client *client, u8 reg, u8 value)
 64{
 65	u8 buffer[2] = { reg, value };
 66	struct i2c_msg msg;
 67	int err;
 68
 69	msg.addr = client->addr;
 70	msg.flags = 0;
 71	msg.len = sizeof(buffer);
 72	msg.buf = buffer;
 73
 74	err = i2c_transfer(client->adapter, &msg, 1);
 75	if (err < 0)
 76		return err;
 77
 78	return 0;
 79}
 80
 81static int pcf8523_voltage_low(struct i2c_client *client)
 82{
 83	u8 value;
 84	int err;
 85
 86	err = pcf8523_read(client, REG_CONTROL3, &value);
 87	if (err < 0)
 88		return err;
 89
 90	return !!(value & REG_CONTROL3_BLF);
 91}
 92
 93static int pcf8523_load_capacitance(struct i2c_client *client)
 94{
 95	u32 load;
 96	u8 value;
 97	int err;
 98
 99	err = pcf8523_read(client, REG_CONTROL1, &value);
100	if (err < 0)
101		return err;
102
103	load = 12500;
104	of_property_read_u32(client->dev.of_node, "quartz-load-femtofarads",
105			     &load);
106
107	switch (load) {
108	default:
109		dev_warn(&client->dev, "Unknown quartz-load-femtofarads value: %d. Assuming 12500",
110			 load);
111		fallthrough;
112	case 12500:
113		value |= REG_CONTROL1_CAP_SEL;
114		break;
115	case 7000:
116		value &= ~REG_CONTROL1_CAP_SEL;
117		break;
118	}
119
120	err = pcf8523_write(client, REG_CONTROL1, value);
121
122	return err;
123}
124
125static int pcf8523_set_pm(struct i2c_client *client, u8 pm)
126{
127	u8 value;
128	int err;
129
130	err = pcf8523_read(client, REG_CONTROL3, &value);
131	if (err < 0)
132		return err;
133
134	value = (value & ~REG_CONTROL3_PM_MASK) | pm;
135
136	err = pcf8523_write(client, REG_CONTROL3, value);
137	if (err < 0)
138		return err;
139
140	return 0;
141}
142
143static int pcf8523_stop_rtc(struct i2c_client *client)
144{
145	u8 value;
146	int err;
147
148	err = pcf8523_read(client, REG_CONTROL1, &value);
149	if (err < 0)
150		return err;
151
152	value |= REG_CONTROL1_STOP;
153
154	err = pcf8523_write(client, REG_CONTROL1, value);
155	if (err < 0)
156		return err;
157
158	return 0;
159}
160
161static int pcf8523_start_rtc(struct i2c_client *client)
162{
163	u8 value;
164	int err;
165
166	err = pcf8523_read(client, REG_CONTROL1, &value);
167	if (err < 0)
168		return err;
169
170	value &= ~REG_CONTROL1_STOP;
171
172	err = pcf8523_write(client, REG_CONTROL1, value);
173	if (err < 0)
174		return err;
175
176	return 0;
177}
178
179static int pcf8523_rtc_read_time(struct device *dev, struct rtc_time *tm)
180{
181	struct i2c_client *client = to_i2c_client(dev);
182	u8 start = REG_SECONDS, regs[7];
183	struct i2c_msg msgs[2];
184	int err;
185
186	err = pcf8523_voltage_low(client);
187	if (err < 0) {
188		return err;
189	} else if (err > 0) {
190		dev_err(dev, "low voltage detected, time is unreliable\n");
191		return -EINVAL;
192	}
193
194	msgs[0].addr = client->addr;
195	msgs[0].flags = 0;
196	msgs[0].len = 1;
197	msgs[0].buf = &start;
198
199	msgs[1].addr = client->addr;
200	msgs[1].flags = I2C_M_RD;
201	msgs[1].len = sizeof(regs);
202	msgs[1].buf = regs;
203
204	err = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
205	if (err < 0)
206		return err;
207
208	if (regs[0] & REG_SECONDS_OS)
209		return -EINVAL;
210
211	tm->tm_sec = bcd2bin(regs[0] & 0x7f);
212	tm->tm_min = bcd2bin(regs[1] & 0x7f);
213	tm->tm_hour = bcd2bin(regs[2] & 0x3f);
214	tm->tm_mday = bcd2bin(regs[3] & 0x3f);
215	tm->tm_wday = regs[4] & 0x7;
216	tm->tm_mon = bcd2bin(regs[5] & 0x1f) - 1;
217	tm->tm_year = bcd2bin(regs[6]) + 100;
218
219	return 0;
220}
221
222static int pcf8523_rtc_set_time(struct device *dev, struct rtc_time *tm)
223{
224	struct i2c_client *client = to_i2c_client(dev);
225	struct i2c_msg msg;
226	u8 regs[8];
227	int err;
228
229	/*
230	 * The hardware can only store values between 0 and 99 in it's YEAR
231	 * register (with 99 overflowing to 0 on increment).
232	 * After 2100-02-28 we could start interpreting the year to be in the
233	 * interval [2100, 2199], but there is no path to switch in a smooth way
234	 * because the chip handles YEAR=0x00 (and the out-of-spec
235	 * YEAR=0xa0) as a leap year, but 2100 isn't.
236	 */
237	if (tm->tm_year < 100 || tm->tm_year >= 200)
238		return -EINVAL;
239
240	err = pcf8523_stop_rtc(client);
241	if (err < 0)
242		return err;
243
244	regs[0] = REG_SECONDS;
245	/* This will purposely overwrite REG_SECONDS_OS */
246	regs[1] = bin2bcd(tm->tm_sec);
247	regs[2] = bin2bcd(tm->tm_min);
248	regs[3] = bin2bcd(tm->tm_hour);
249	regs[4] = bin2bcd(tm->tm_mday);
250	regs[5] = tm->tm_wday;
251	regs[6] = bin2bcd(tm->tm_mon + 1);
252	regs[7] = bin2bcd(tm->tm_year - 100);
253
254	msg.addr = client->addr;
255	msg.flags = 0;
256	msg.len = sizeof(regs);
257	msg.buf = regs;
258
259	err = i2c_transfer(client->adapter, &msg, 1);
260	if (err < 0) {
261		/*
262		 * If the time cannot be set, restart the RTC anyway. Note
263		 * that errors are ignored if the RTC cannot be started so
264		 * that we have a chance to propagate the original error.
265		 */
266		pcf8523_start_rtc(client);
267		return err;
268	}
269
270	return pcf8523_start_rtc(client);
271}
272
273#ifdef CONFIG_RTC_INTF_DEV
274static int pcf8523_rtc_ioctl(struct device *dev, unsigned int cmd,
275			     unsigned long arg)
276{
277	struct i2c_client *client = to_i2c_client(dev);
278	int ret;
279
280	switch (cmd) {
281	case RTC_VL_READ:
282		ret = pcf8523_voltage_low(client);
283		if (ret < 0)
284			return ret;
285		if (ret)
286			ret = RTC_VL_BACKUP_LOW;
287
288		return put_user(ret, (unsigned int __user *)arg);
289
290	default:
291		return -ENOIOCTLCMD;
292	}
293}
294#else
295#define pcf8523_rtc_ioctl NULL
296#endif
297
298static int pcf8523_rtc_read_offset(struct device *dev, long *offset)
299{
300	struct i2c_client *client = to_i2c_client(dev);
301	int err;
302	u8 value;
303	s8 val;
304
305	err = pcf8523_read(client, REG_OFFSET, &value);
306	if (err < 0)
307		return err;
308
309	/* sign extend the 7-bit offset value */
310	val = value << 1;
311	*offset = (value & REG_OFFSET_MODE ? 4069 : 4340) * (val >> 1);
312
313	return 0;
314}
315
316static int pcf8523_rtc_set_offset(struct device *dev, long offset)
317{
318	struct i2c_client *client = to_i2c_client(dev);
319	long reg_m0, reg_m1;
320	u8 value;
321
322	reg_m0 = clamp(DIV_ROUND_CLOSEST(offset, 4340), -64L, 63L);
323	reg_m1 = clamp(DIV_ROUND_CLOSEST(offset, 4069), -64L, 63L);
324
325	if (abs(reg_m0 * 4340 - offset) < abs(reg_m1 * 4069 - offset))
326		value = reg_m0 & 0x7f;
327	else
328		value = (reg_m1 & 0x7f) | REG_OFFSET_MODE;
329
330	return pcf8523_write(client, REG_OFFSET, value);
331}
332
333static const struct rtc_class_ops pcf8523_rtc_ops = {
334	.read_time = pcf8523_rtc_read_time,
335	.set_time = pcf8523_rtc_set_time,
336	.ioctl = pcf8523_rtc_ioctl,
337	.read_offset = pcf8523_rtc_read_offset,
338	.set_offset = pcf8523_rtc_set_offset,
339};
340
341static int pcf8523_probe(struct i2c_client *client,
342			 const struct i2c_device_id *id)
343{
344	struct rtc_device *rtc;
345	int err;
346
347	if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
348		return -ENODEV;
349
350	err = pcf8523_load_capacitance(client);
351	if (err < 0)
352		dev_warn(&client->dev, "failed to set xtal load capacitance: %d",
353			 err);
354
355	err = pcf8523_set_pm(client, 0);
356	if (err < 0)
357		return err;
358
359	rtc = devm_rtc_device_register(&client->dev, DRIVER_NAME,
360				       &pcf8523_rtc_ops, THIS_MODULE);
361	if (IS_ERR(rtc))
362		return PTR_ERR(rtc);
363
364	return 0;
365}
366
367static const struct i2c_device_id pcf8523_id[] = {
368	{ "pcf8523", 0 },
369	{ }
370};
371MODULE_DEVICE_TABLE(i2c, pcf8523_id);
372
373#ifdef CONFIG_OF
374static const struct of_device_id pcf8523_of_match[] = {
375	{ .compatible = "nxp,pcf8523" },
376	{ .compatible = "microcrystal,rv8523" },
377	{ }
378};
379MODULE_DEVICE_TABLE(of, pcf8523_of_match);
380#endif
381
382static struct i2c_driver pcf8523_driver = {
383	.driver = {
384		.name = DRIVER_NAME,
385		.of_match_table = of_match_ptr(pcf8523_of_match),
386	},
387	.probe = pcf8523_probe,
388	.id_table = pcf8523_id,
389};
390module_i2c_driver(pcf8523_driver);
391
392MODULE_AUTHOR("Thierry Reding <thierry.reding@avionic-design.de>");
393MODULE_DESCRIPTION("NXP PCF8523 RTC driver");
394MODULE_LICENSE("GPL v2");