xref: /openbmc/linux/drivers/misc/eeprom/at24.c (revision a8c5cb99)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * at24.c - handle most I2C EEPROMs
4  *
5  * Copyright (C) 2005-2007 David Brownell
6  * Copyright (C) 2008 Wolfram Sang, Pengutronix
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/init.h>
11 #include <linux/module.h>
12 #include <linux/of_device.h>
13 #include <linux/slab.h>
14 #include <linux/delay.h>
15 #include <linux/mutex.h>
16 #include <linux/mod_devicetable.h>
17 #include <linux/log2.h>
18 #include <linux/bitops.h>
19 #include <linux/jiffies.h>
20 #include <linux/property.h>
21 #include <linux/acpi.h>
22 #include <linux/i2c.h>
23 #include <linux/nvmem-provider.h>
24 #include <linux/regmap.h>
25 #include <linux/platform_data/at24.h>
26 #include <linux/pm_runtime.h>
27 #include <linux/gpio/consumer.h>
28 
29 /*
30  * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
31  * Differences between different vendor product lines (like Atmel AT24C or
32  * MicroChip 24LC, etc) won't much matter for typical read/write access.
33  * There are also I2C RAM chips, likewise interchangeable. One example
34  * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
35  *
36  * However, misconfiguration can lose data. "Set 16-bit memory address"
37  * to a part with 8-bit addressing will overwrite data. Writing with too
38  * big a page size also loses data. And it's not safe to assume that the
39  * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
40  * uses 0x51, for just one example.
41  *
42  * Accordingly, explicit board-specific configuration data should be used
43  * in almost all cases. (One partial exception is an SMBus used to access
44  * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
45  *
46  * So this driver uses "new style" I2C driver binding, expecting to be
47  * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
48  * similar kernel-resident tables; or, configuration data coming from
49  * a bootloader.
50  *
51  * Other than binding model, current differences from "eeprom" driver are
52  * that this one handles write access and isn't restricted to 24c02 devices.
53  * It also handles larger devices (32 kbit and up) with two-byte addresses,
54  * which won't work on pure SMBus systems.
55  */
56 
57 struct at24_client {
58 	struct i2c_client *client;
59 	struct regmap *regmap;
60 };
61 
62 struct at24_data {
63 	/*
64 	 * Lock protects against activities from other Linux tasks,
65 	 * but not from changes by other I2C masters.
66 	 */
67 	struct mutex lock;
68 
69 	unsigned int write_max;
70 	unsigned int num_addresses;
71 	unsigned int offset_adj;
72 
73 	u32 byte_len;
74 	u16 page_size;
75 	u8 flags;
76 
77 	struct nvmem_device *nvmem;
78 
79 	struct gpio_desc *wp_gpio;
80 
81 	/*
82 	 * Some chips tie up multiple I2C addresses; dummy devices reserve
83 	 * them for us, and we'll use them with SMBus calls.
84 	 */
85 	struct at24_client client[];
86 };
87 
88 /*
89  * This parameter is to help this driver avoid blocking other drivers out
90  * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
91  * clock, one 256 byte read takes about 1/43 second which is excessive;
92  * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
93  * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
94  *
95  * This value is forced to be a power of two so that writes align on pages.
96  */
97 static unsigned int at24_io_limit = 128;
98 module_param_named(io_limit, at24_io_limit, uint, 0);
99 MODULE_PARM_DESC(at24_io_limit, "Maximum bytes per I/O (default 128)");
100 
101 /*
102  * Specs often allow 5 msec for a page write, sometimes 20 msec;
103  * it's important to recover from write timeouts.
104  */
105 static unsigned int at24_write_timeout = 25;
106 module_param_named(write_timeout, at24_write_timeout, uint, 0);
107 MODULE_PARM_DESC(at24_write_timeout, "Time (in ms) to try writes (default 25)");
108 
109 /*
110  * Both reads and writes fail if the previous write didn't complete yet. This
111  * macro loops a few times waiting at least long enough for one entire page
112  * write to work while making sure that at least one iteration is run before
113  * checking the break condition.
114  *
115  * It takes two parameters: a variable in which the future timeout in jiffies
116  * will be stored and a temporary variable holding the time of the last
117  * iteration of processing the request. Both should be unsigned integers
118  * holding at least 32 bits.
119  */
120 #define at24_loop_until_timeout(tout, op_time)				\
121 	for (tout = jiffies + msecs_to_jiffies(at24_write_timeout),	\
122 	     op_time = 0;						\
123 	     op_time ? time_before(op_time, tout) : true;		\
124 	     usleep_range(1000, 1500), op_time = jiffies)
125 
126 struct at24_chip_data {
127 	/*
128 	 * these fields mirror their equivalents in
129 	 * struct at24_platform_data
130 	 */
131 	u32 byte_len;
132 	u8 flags;
133 };
134 
135 #define AT24_CHIP_DATA(_name, _len, _flags)				\
136 	static const struct at24_chip_data _name = {			\
137 		.byte_len = _len, .flags = _flags,			\
138 	}
139 
140 /* needs 8 addresses as A0-A2 are ignored */
141 AT24_CHIP_DATA(at24_data_24c00, 128 / 8, AT24_FLAG_TAKE8ADDR);
142 /* old variants can't be handled with this generic entry! */
143 AT24_CHIP_DATA(at24_data_24c01, 1024 / 8, 0);
144 AT24_CHIP_DATA(at24_data_24cs01, 16,
145 	AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
146 AT24_CHIP_DATA(at24_data_24c02, 2048 / 8, 0);
147 AT24_CHIP_DATA(at24_data_24cs02, 16,
148 	AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
149 AT24_CHIP_DATA(at24_data_24mac402, 48 / 8,
150 	AT24_FLAG_MAC | AT24_FLAG_READONLY);
151 AT24_CHIP_DATA(at24_data_24mac602, 64 / 8,
152 	AT24_FLAG_MAC | AT24_FLAG_READONLY);
153 /* spd is a 24c02 in memory DIMMs */
154 AT24_CHIP_DATA(at24_data_spd, 2048 / 8,
155 	AT24_FLAG_READONLY | AT24_FLAG_IRUGO);
156 AT24_CHIP_DATA(at24_data_24c04, 4096 / 8, 0);
157 AT24_CHIP_DATA(at24_data_24cs04, 16,
158 	AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
159 /* 24rf08 quirk is handled at i2c-core */
160 AT24_CHIP_DATA(at24_data_24c08, 8192 / 8, 0);
161 AT24_CHIP_DATA(at24_data_24cs08, 16,
162 	AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
163 AT24_CHIP_DATA(at24_data_24c16, 16384 / 8, 0);
164 AT24_CHIP_DATA(at24_data_24cs16, 16,
165 	AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
166 AT24_CHIP_DATA(at24_data_24c32, 32768 / 8, AT24_FLAG_ADDR16);
167 AT24_CHIP_DATA(at24_data_24cs32, 16,
168 	AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
169 AT24_CHIP_DATA(at24_data_24c64, 65536 / 8, AT24_FLAG_ADDR16);
170 AT24_CHIP_DATA(at24_data_24cs64, 16,
171 	AT24_FLAG_ADDR16 | AT24_FLAG_SERIAL | AT24_FLAG_READONLY);
172 AT24_CHIP_DATA(at24_data_24c128, 131072 / 8, AT24_FLAG_ADDR16);
173 AT24_CHIP_DATA(at24_data_24c256, 262144 / 8, AT24_FLAG_ADDR16);
174 AT24_CHIP_DATA(at24_data_24c512, 524288 / 8, AT24_FLAG_ADDR16);
175 AT24_CHIP_DATA(at24_data_24c1024, 1048576 / 8, AT24_FLAG_ADDR16);
176 /* identical to 24c08 ? */
177 AT24_CHIP_DATA(at24_data_INT3499, 8192 / 8, 0);
178 
179 static const struct i2c_device_id at24_ids[] = {
180 	{ "24c00",	(kernel_ulong_t)&at24_data_24c00 },
181 	{ "24c01",	(kernel_ulong_t)&at24_data_24c01 },
182 	{ "24cs01",	(kernel_ulong_t)&at24_data_24cs01 },
183 	{ "24c02",	(kernel_ulong_t)&at24_data_24c02 },
184 	{ "24cs02",	(kernel_ulong_t)&at24_data_24cs02 },
185 	{ "24mac402",	(kernel_ulong_t)&at24_data_24mac402 },
186 	{ "24mac602",	(kernel_ulong_t)&at24_data_24mac602 },
187 	{ "spd",	(kernel_ulong_t)&at24_data_spd },
188 	{ "24c04",	(kernel_ulong_t)&at24_data_24c04 },
189 	{ "24cs04",	(kernel_ulong_t)&at24_data_24cs04 },
190 	{ "24c08",	(kernel_ulong_t)&at24_data_24c08 },
191 	{ "24cs08",	(kernel_ulong_t)&at24_data_24cs08 },
192 	{ "24c16",	(kernel_ulong_t)&at24_data_24c16 },
193 	{ "24cs16",	(kernel_ulong_t)&at24_data_24cs16 },
194 	{ "24c32",	(kernel_ulong_t)&at24_data_24c32 },
195 	{ "24cs32",	(kernel_ulong_t)&at24_data_24cs32 },
196 	{ "24c64",	(kernel_ulong_t)&at24_data_24c64 },
197 	{ "24cs64",	(kernel_ulong_t)&at24_data_24cs64 },
198 	{ "24c128",	(kernel_ulong_t)&at24_data_24c128 },
199 	{ "24c256",	(kernel_ulong_t)&at24_data_24c256 },
200 	{ "24c512",	(kernel_ulong_t)&at24_data_24c512 },
201 	{ "24c1024",	(kernel_ulong_t)&at24_data_24c1024 },
202 	{ "at24",	0 },
203 	{ /* END OF LIST */ }
204 };
205 MODULE_DEVICE_TABLE(i2c, at24_ids);
206 
207 static const struct of_device_id at24_of_match[] = {
208 	{ .compatible = "atmel,24c00",		.data = &at24_data_24c00 },
209 	{ .compatible = "atmel,24c01",		.data = &at24_data_24c01 },
210 	{ .compatible = "atmel,24cs01",		.data = &at24_data_24cs01 },
211 	{ .compatible = "atmel,24c02",		.data = &at24_data_24c02 },
212 	{ .compatible = "atmel,24cs02",		.data = &at24_data_24cs02 },
213 	{ .compatible = "atmel,24mac402",	.data = &at24_data_24mac402 },
214 	{ .compatible = "atmel,24mac602",	.data = &at24_data_24mac602 },
215 	{ .compatible = "atmel,spd",		.data = &at24_data_spd },
216 	{ .compatible = "atmel,24c04",		.data = &at24_data_24c04 },
217 	{ .compatible = "atmel,24cs04",		.data = &at24_data_24cs04 },
218 	{ .compatible = "atmel,24c08",		.data = &at24_data_24c08 },
219 	{ .compatible = "atmel,24cs08",		.data = &at24_data_24cs08 },
220 	{ .compatible = "atmel,24c16",		.data = &at24_data_24c16 },
221 	{ .compatible = "atmel,24cs16",		.data = &at24_data_24cs16 },
222 	{ .compatible = "atmel,24c32",		.data = &at24_data_24c32 },
223 	{ .compatible = "atmel,24cs32",		.data = &at24_data_24cs32 },
224 	{ .compatible = "atmel,24c64",		.data = &at24_data_24c64 },
225 	{ .compatible = "atmel,24cs64",		.data = &at24_data_24cs64 },
226 	{ .compatible = "atmel,24c128",		.data = &at24_data_24c128 },
227 	{ .compatible = "atmel,24c256",		.data = &at24_data_24c256 },
228 	{ .compatible = "atmel,24c512",		.data = &at24_data_24c512 },
229 	{ .compatible = "atmel,24c1024",	.data = &at24_data_24c1024 },
230 	{ /* END OF LIST */ },
231 };
232 MODULE_DEVICE_TABLE(of, at24_of_match);
233 
234 static const struct acpi_device_id at24_acpi_ids[] = {
235 	{ "INT3499",	(kernel_ulong_t)&at24_data_INT3499 },
236 	{ /* END OF LIST */ }
237 };
238 MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
239 
240 /*
241  * This routine supports chips which consume multiple I2C addresses. It
242  * computes the addressing information to be used for a given r/w request.
243  * Assumes that sanity checks for offset happened at sysfs-layer.
244  *
245  * Slave address and byte offset derive from the offset. Always
246  * set the byte address; on a multi-master board, another master
247  * may have changed the chip's "current" address pointer.
248  */
249 static struct at24_client *at24_translate_offset(struct at24_data *at24,
250 						 unsigned int *offset)
251 {
252 	unsigned int i;
253 
254 	if (at24->flags & AT24_FLAG_ADDR16) {
255 		i = *offset >> 16;
256 		*offset &= 0xffff;
257 	} else {
258 		i = *offset >> 8;
259 		*offset &= 0xff;
260 	}
261 
262 	return &at24->client[i];
263 }
264 
265 static struct device *at24_base_client_dev(struct at24_data *at24)
266 {
267 	return &at24->client[0].client->dev;
268 }
269 
270 static size_t at24_adjust_read_count(struct at24_data *at24,
271 				      unsigned int offset, size_t count)
272 {
273 	unsigned int bits;
274 	size_t remainder;
275 
276 	/*
277 	 * In case of multi-address chips that don't rollover reads to
278 	 * the next slave address: truncate the count to the slave boundary,
279 	 * so that the read never straddles slaves.
280 	 */
281 	if (at24->flags & AT24_FLAG_NO_RDROL) {
282 		bits = (at24->flags & AT24_FLAG_ADDR16) ? 16 : 8;
283 		remainder = BIT(bits) - offset;
284 		if (count > remainder)
285 			count = remainder;
286 	}
287 
288 	if (count > at24_io_limit)
289 		count = at24_io_limit;
290 
291 	return count;
292 }
293 
294 static ssize_t at24_regmap_read(struct at24_data *at24, char *buf,
295 				unsigned int offset, size_t count)
296 {
297 	unsigned long timeout, read_time;
298 	struct at24_client *at24_client;
299 	struct i2c_client *client;
300 	struct regmap *regmap;
301 	int ret;
302 
303 	at24_client = at24_translate_offset(at24, &offset);
304 	regmap = at24_client->regmap;
305 	client = at24_client->client;
306 	count = at24_adjust_read_count(at24, offset, count);
307 
308 	/* adjust offset for mac and serial read ops */
309 	offset += at24->offset_adj;
310 
311 	at24_loop_until_timeout(timeout, read_time) {
312 		ret = regmap_bulk_read(regmap, offset, buf, count);
313 		dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
314 			count, offset, ret, jiffies);
315 		if (!ret)
316 			return count;
317 	}
318 
319 	return -ETIMEDOUT;
320 }
321 
322 /*
323  * Note that if the hardware write-protect pin is pulled high, the whole
324  * chip is normally write protected. But there are plenty of product
325  * variants here, including OTP fuses and partial chip protect.
326  *
327  * We only use page mode writes; the alternative is sloooow. These routines
328  * write at most one page.
329  */
330 
331 static size_t at24_adjust_write_count(struct at24_data *at24,
332 				      unsigned int offset, size_t count)
333 {
334 	unsigned int next_page;
335 
336 	/* write_max is at most a page */
337 	if (count > at24->write_max)
338 		count = at24->write_max;
339 
340 	/* Never roll over backwards, to the start of this page */
341 	next_page = roundup(offset + 1, at24->page_size);
342 	if (offset + count > next_page)
343 		count = next_page - offset;
344 
345 	return count;
346 }
347 
348 static ssize_t at24_regmap_write(struct at24_data *at24, const char *buf,
349 				 unsigned int offset, size_t count)
350 {
351 	unsigned long timeout, write_time;
352 	struct at24_client *at24_client;
353 	struct i2c_client *client;
354 	struct regmap *regmap;
355 	int ret;
356 
357 	at24_client = at24_translate_offset(at24, &offset);
358 	regmap = at24_client->regmap;
359 	client = at24_client->client;
360 	count = at24_adjust_write_count(at24, offset, count);
361 
362 	at24_loop_until_timeout(timeout, write_time) {
363 		ret = regmap_bulk_write(regmap, offset, buf, count);
364 		dev_dbg(&client->dev, "write %zu@%d --> %d (%ld)\n",
365 			count, offset, ret, jiffies);
366 		if (!ret)
367 			return count;
368 	}
369 
370 	return -ETIMEDOUT;
371 }
372 
373 static int at24_read(void *priv, unsigned int off, void *val, size_t count)
374 {
375 	struct at24_data *at24;
376 	struct device *dev;
377 	char *buf = val;
378 	int ret;
379 
380 	at24 = priv;
381 	dev = at24_base_client_dev(at24);
382 
383 	if (unlikely(!count))
384 		return count;
385 
386 	if (off + count > at24->byte_len)
387 		return -EINVAL;
388 
389 	ret = pm_runtime_get_sync(dev);
390 	if (ret < 0) {
391 		pm_runtime_put_noidle(dev);
392 		return ret;
393 	}
394 
395 	/*
396 	 * Read data from chip, protecting against concurrent updates
397 	 * from this host, but not from other I2C masters.
398 	 */
399 	mutex_lock(&at24->lock);
400 
401 	while (count) {
402 		ret = at24_regmap_read(at24, buf, off, count);
403 		if (ret < 0) {
404 			mutex_unlock(&at24->lock);
405 			pm_runtime_put(dev);
406 			return ret;
407 		}
408 		buf += ret;
409 		off += ret;
410 		count -= ret;
411 	}
412 
413 	mutex_unlock(&at24->lock);
414 
415 	pm_runtime_put(dev);
416 
417 	return 0;
418 }
419 
420 static int at24_write(void *priv, unsigned int off, void *val, size_t count)
421 {
422 	struct at24_data *at24;
423 	struct device *dev;
424 	char *buf = val;
425 	int ret;
426 
427 	at24 = priv;
428 	dev = at24_base_client_dev(at24);
429 
430 	if (unlikely(!count))
431 		return -EINVAL;
432 
433 	if (off + count > at24->byte_len)
434 		return -EINVAL;
435 
436 	ret = pm_runtime_get_sync(dev);
437 	if (ret < 0) {
438 		pm_runtime_put_noidle(dev);
439 		return ret;
440 	}
441 
442 	/*
443 	 * Write data to chip, protecting against concurrent updates
444 	 * from this host, but not from other I2C masters.
445 	 */
446 	mutex_lock(&at24->lock);
447 	gpiod_set_value_cansleep(at24->wp_gpio, 0);
448 
449 	while (count) {
450 		ret = at24_regmap_write(at24, buf, off, count);
451 		if (ret < 0) {
452 			gpiod_set_value_cansleep(at24->wp_gpio, 1);
453 			mutex_unlock(&at24->lock);
454 			pm_runtime_put(dev);
455 			return ret;
456 		}
457 		buf += ret;
458 		off += ret;
459 		count -= ret;
460 	}
461 
462 	gpiod_set_value_cansleep(at24->wp_gpio, 1);
463 	mutex_unlock(&at24->lock);
464 
465 	pm_runtime_put(dev);
466 
467 	return 0;
468 }
469 
470 static void at24_properties_to_pdata(struct device *dev,
471 				     struct at24_platform_data *chip)
472 {
473 	int err;
474 	u32 val;
475 
476 	if (device_property_present(dev, "read-only"))
477 		chip->flags |= AT24_FLAG_READONLY;
478 	if (device_property_present(dev, "no-read-rollover"))
479 		chip->flags |= AT24_FLAG_NO_RDROL;
480 
481 	err = device_property_read_u32(dev, "size", &val);
482 	if (!err)
483 		chip->byte_len = val;
484 
485 	err = device_property_read_u32(dev, "pagesize", &val);
486 	if (!err) {
487 		chip->page_size = val;
488 	} else {
489 		/*
490 		 * This is slow, but we can't know all eeproms, so we better
491 		 * play safe. Specifying custom eeprom-types via platform_data
492 		 * is recommended anyhow.
493 		 */
494 		chip->page_size = 1;
495 	}
496 }
497 
498 static int at24_get_pdata(struct device *dev, struct at24_platform_data *pdata)
499 {
500 	struct device_node *of_node = dev->of_node;
501 	const struct at24_chip_data *cdata;
502 	const struct i2c_device_id *id;
503 	struct at24_platform_data *pd;
504 
505 	pd = dev_get_platdata(dev);
506 	if (pd) {
507 		memcpy(pdata, pd, sizeof(*pdata));
508 		return 0;
509 	}
510 
511 	id = i2c_match_id(at24_ids, to_i2c_client(dev));
512 
513 	/*
514 	 * The I2C core allows OF nodes compatibles to match against the
515 	 * I2C device ID table as a fallback, so check not only if an OF
516 	 * node is present but also if it matches an OF device ID entry.
517 	 */
518 	if (of_node && of_match_device(at24_of_match, dev))
519 		cdata = of_device_get_match_data(dev);
520 	else if (id)
521 		cdata = (void *)id->driver_data;
522 	else
523 		cdata = acpi_device_get_match_data(dev);
524 
525 	if (!cdata)
526 		return -ENODEV;
527 
528 	pdata->byte_len = cdata->byte_len;
529 	pdata->flags = cdata->flags;
530 	at24_properties_to_pdata(dev, pdata);
531 
532 	return 0;
533 }
534 
535 static void at24_remove_dummy_clients(struct at24_data *at24)
536 {
537 	int i;
538 
539 	for (i = 1; i < at24->num_addresses; i++)
540 		i2c_unregister_device(at24->client[i].client);
541 }
542 
543 static int at24_make_dummy_client(struct at24_data *at24, unsigned int index,
544 				  struct regmap_config *regmap_config)
545 {
546 	struct i2c_client *base_client, *dummy_client;
547 	unsigned short int addr;
548 	struct regmap *regmap;
549 	struct device *dev;
550 
551 	base_client = at24->client[0].client;
552 	dev = &base_client->dev;
553 	addr = base_client->addr + index;
554 
555 	dummy_client = i2c_new_dummy(base_client->adapter,
556 				     base_client->addr + index);
557 	if (!dummy_client) {
558 		dev_err(dev, "address 0x%02x unavailable\n", addr);
559 		return -EADDRINUSE;
560 	}
561 
562 	regmap = devm_regmap_init_i2c(dummy_client, regmap_config);
563 	if (IS_ERR(regmap)) {
564 		i2c_unregister_device(dummy_client);
565 		return PTR_ERR(regmap);
566 	}
567 
568 	at24->client[index].client = dummy_client;
569 	at24->client[index].regmap = regmap;
570 
571 	return 0;
572 }
573 
574 static unsigned int at24_get_offset_adj(u8 flags, unsigned int byte_len)
575 {
576 	if (flags & AT24_FLAG_MAC) {
577 		/* EUI-48 starts from 0x9a, EUI-64 from 0x98 */
578 		return 0xa0 - byte_len;
579 	} else if (flags & AT24_FLAG_SERIAL && flags & AT24_FLAG_ADDR16) {
580 		/*
581 		 * For 16 bit address pointers, the word address must contain
582 		 * a '10' sequence in bits 11 and 10 regardless of the
583 		 * intended position of the address pointer.
584 		 */
585 		return 0x0800;
586 	} else if (flags & AT24_FLAG_SERIAL) {
587 		/*
588 		 * Otherwise the word address must begin with a '10' sequence,
589 		 * regardless of the intended address.
590 		 */
591 		return 0x0080;
592 	} else {
593 		return 0;
594 	}
595 }
596 
597 static int at24_probe(struct i2c_client *client)
598 {
599 	struct regmap_config regmap_config = { };
600 	struct nvmem_config nvmem_config = { };
601 	struct at24_platform_data pdata = { };
602 	struct device *dev = &client->dev;
603 	bool i2c_fn_i2c, i2c_fn_block;
604 	unsigned int i, num_addresses;
605 	struct at24_data *at24;
606 	struct regmap *regmap;
607 	size_t at24_size;
608 	bool writable;
609 	u8 test_byte;
610 	int err;
611 
612 	i2c_fn_i2c = i2c_check_functionality(client->adapter, I2C_FUNC_I2C);
613 	i2c_fn_block = i2c_check_functionality(client->adapter,
614 					       I2C_FUNC_SMBUS_WRITE_I2C_BLOCK);
615 
616 	err = at24_get_pdata(dev, &pdata);
617 	if (err)
618 		return err;
619 
620 	if (!i2c_fn_i2c && !i2c_fn_block)
621 		pdata.page_size = 1;
622 
623 	if (!pdata.page_size) {
624 		dev_err(dev, "page_size must not be 0!\n");
625 		return -EINVAL;
626 	}
627 
628 	if (!is_power_of_2(pdata.page_size))
629 		dev_warn(dev, "page_size looks suspicious (no power of 2)!\n");
630 
631 	if (pdata.flags & AT24_FLAG_TAKE8ADDR)
632 		num_addresses = 8;
633 	else
634 		num_addresses =	DIV_ROUND_UP(pdata.byte_len,
635 			(pdata.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
636 
637 	if ((pdata.flags & AT24_FLAG_SERIAL) && (pdata.flags & AT24_FLAG_MAC)) {
638 		dev_err(dev,
639 			"invalid device data - cannot have both AT24_FLAG_SERIAL & AT24_FLAG_MAC.");
640 		return -EINVAL;
641 	}
642 
643 	regmap_config.val_bits = 8;
644 	regmap_config.reg_bits = (pdata.flags & AT24_FLAG_ADDR16) ? 16 : 8;
645 	regmap_config.disable_locking = true;
646 
647 	regmap = devm_regmap_init_i2c(client, &regmap_config);
648 	if (IS_ERR(regmap))
649 		return PTR_ERR(regmap);
650 
651 	at24_size = sizeof(*at24) + num_addresses * sizeof(struct at24_client);
652 	at24 = devm_kzalloc(dev, at24_size, GFP_KERNEL);
653 	if (!at24)
654 		return -ENOMEM;
655 
656 	mutex_init(&at24->lock);
657 	at24->byte_len = pdata.byte_len;
658 	at24->page_size = pdata.page_size;
659 	at24->flags = pdata.flags;
660 	at24->num_addresses = num_addresses;
661 	at24->offset_adj = at24_get_offset_adj(pdata.flags, pdata.byte_len);
662 	at24->client[0].client = client;
663 	at24->client[0].regmap = regmap;
664 
665 	at24->wp_gpio = devm_gpiod_get_optional(dev, "wp", GPIOD_OUT_HIGH);
666 	if (IS_ERR(at24->wp_gpio))
667 		return PTR_ERR(at24->wp_gpio);
668 
669 	writable = !(pdata.flags & AT24_FLAG_READONLY);
670 	if (writable) {
671 		at24->write_max = min_t(unsigned int,
672 					pdata.page_size, at24_io_limit);
673 		if (!i2c_fn_i2c && at24->write_max > I2C_SMBUS_BLOCK_MAX)
674 			at24->write_max = I2C_SMBUS_BLOCK_MAX;
675 	}
676 
677 	/* use dummy devices for multiple-address chips */
678 	for (i = 1; i < num_addresses; i++) {
679 		err = at24_make_dummy_client(at24, i, &regmap_config);
680 		if (err) {
681 			at24_remove_dummy_clients(at24);
682 			return err;
683 		}
684 	}
685 
686 	i2c_set_clientdata(client, at24);
687 
688 	/* enable runtime pm */
689 	pm_runtime_set_active(dev);
690 	pm_runtime_enable(dev);
691 
692 	/*
693 	 * Perform a one-byte test read to verify that the
694 	 * chip is functional.
695 	 */
696 	err = at24_read(at24, 0, &test_byte, 1);
697 	pm_runtime_idle(dev);
698 	if (err) {
699 		err = -ENODEV;
700 		goto err_clients;
701 	}
702 
703 	nvmem_config.name = dev_name(dev);
704 	nvmem_config.dev = dev;
705 	nvmem_config.read_only = !writable;
706 	nvmem_config.root_only = true;
707 	nvmem_config.owner = THIS_MODULE;
708 	nvmem_config.compat = true;
709 	nvmem_config.base_dev = dev;
710 	nvmem_config.reg_read = at24_read;
711 	nvmem_config.reg_write = at24_write;
712 	nvmem_config.priv = at24;
713 	nvmem_config.stride = 1;
714 	nvmem_config.word_size = 1;
715 	nvmem_config.size = pdata.byte_len;
716 
717 	at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
718 	if (IS_ERR(at24->nvmem)) {
719 		err = PTR_ERR(at24->nvmem);
720 		goto err_clients;
721 	}
722 
723 	dev_info(dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
724 		 pdata.byte_len, client->name,
725 		 writable ? "writable" : "read-only", at24->write_max);
726 
727 	/* export data to kernel code */
728 	if (pdata.setup)
729 		pdata.setup(at24->nvmem, pdata.context);
730 
731 	return 0;
732 
733 err_clients:
734 	at24_remove_dummy_clients(at24);
735 	pm_runtime_disable(dev);
736 
737 	return err;
738 }
739 
740 static int at24_remove(struct i2c_client *client)
741 {
742 	struct at24_data *at24;
743 
744 	at24 = i2c_get_clientdata(client);
745 
746 	at24_remove_dummy_clients(at24);
747 	pm_runtime_disable(&client->dev);
748 	pm_runtime_set_suspended(&client->dev);
749 
750 	return 0;
751 }
752 
753 static struct i2c_driver at24_driver = {
754 	.driver = {
755 		.name = "at24",
756 		.of_match_table = at24_of_match,
757 		.acpi_match_table = ACPI_PTR(at24_acpi_ids),
758 	},
759 	.probe_new = at24_probe,
760 	.remove = at24_remove,
761 	.id_table = at24_ids,
762 };
763 
764 static int __init at24_init(void)
765 {
766 	if (!at24_io_limit) {
767 		pr_err("at24: at24_io_limit must not be 0!\n");
768 		return -EINVAL;
769 	}
770 
771 	at24_io_limit = rounddown_pow_of_two(at24_io_limit);
772 	return i2c_add_driver(&at24_driver);
773 }
774 module_init(at24_init);
775 
776 static void __exit at24_exit(void)
777 {
778 	i2c_del_driver(&at24_driver);
779 }
780 module_exit(at24_exit);
781 
782 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
783 MODULE_AUTHOR("David Brownell and Wolfram Sang");
784 MODULE_LICENSE("GPL");
785