xref: /openbmc/linux/drivers/misc/eeprom/at25.c (revision 4800cd83)
1 /*
2  * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
3  *
4  * Copyright (C) 2006 David Brownell
5  *
6  * This program is free software; you can redistribute it and/or modify
7  * it under the terms of the GNU General Public License as published by
8  * the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  */
11 
12 #include <linux/kernel.h>
13 #include <linux/init.h>
14 #include <linux/module.h>
15 #include <linux/slab.h>
16 #include <linux/delay.h>
17 #include <linux/device.h>
18 #include <linux/sched.h>
19 
20 #include <linux/spi/spi.h>
21 #include <linux/spi/eeprom.h>
22 
23 
24 /*
25  * NOTE: this is an *EEPROM* driver.  The vagaries of product naming
26  * mean that some AT25 products are EEPROMs, and others are FLASH.
27  * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver,
28  * not this one!
29  */
30 
31 struct at25_data {
32 	struct spi_device	*spi;
33 	struct memory_accessor	mem;
34 	struct mutex		lock;
35 	struct spi_eeprom	chip;
36 	struct bin_attribute	bin;
37 	unsigned		addrlen;
38 };
39 
40 #define	AT25_WREN	0x06		/* latch the write enable */
41 #define	AT25_WRDI	0x04		/* reset the write enable */
42 #define	AT25_RDSR	0x05		/* read status register */
43 #define	AT25_WRSR	0x01		/* write status register */
44 #define	AT25_READ	0x03		/* read byte(s) */
45 #define	AT25_WRITE	0x02		/* write byte(s)/sector */
46 
47 #define	AT25_SR_nRDY	0x01		/* nRDY = write-in-progress */
48 #define	AT25_SR_WEN	0x02		/* write enable (latched) */
49 #define	AT25_SR_BP0	0x04		/* BP for software writeprotect */
50 #define	AT25_SR_BP1	0x08
51 #define	AT25_SR_WPEN	0x80		/* writeprotect enable */
52 
53 
54 #define EE_MAXADDRLEN	3		/* 24 bit addresses, up to 2 MBytes */
55 
56 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
57  * it's important to recover from write timeouts.
58  */
59 #define	EE_TIMEOUT	25
60 
61 /*-------------------------------------------------------------------------*/
62 
63 #define	io_limit	PAGE_SIZE	/* bytes */
64 
65 static ssize_t
66 at25_ee_read(
67 	struct at25_data	*at25,
68 	char			*buf,
69 	unsigned		offset,
70 	size_t			count
71 )
72 {
73 	u8			command[EE_MAXADDRLEN + 1];
74 	u8			*cp;
75 	ssize_t			status;
76 	struct spi_transfer	t[2];
77 	struct spi_message	m;
78 
79 	if (unlikely(offset >= at25->bin.size))
80 		return 0;
81 	if ((offset + count) > at25->bin.size)
82 		count = at25->bin.size - offset;
83 	if (unlikely(!count))
84 		return count;
85 
86 	cp = command;
87 	*cp++ = AT25_READ;
88 
89 	/* 8/16/24-bit address is written MSB first */
90 	switch (at25->addrlen) {
91 	default:	/* case 3 */
92 		*cp++ = offset >> 16;
93 	case 2:
94 		*cp++ = offset >> 8;
95 	case 1:
96 	case 0:	/* can't happen: for better codegen */
97 		*cp++ = offset >> 0;
98 	}
99 
100 	spi_message_init(&m);
101 	memset(t, 0, sizeof t);
102 
103 	t[0].tx_buf = command;
104 	t[0].len = at25->addrlen + 1;
105 	spi_message_add_tail(&t[0], &m);
106 
107 	t[1].rx_buf = buf;
108 	t[1].len = count;
109 	spi_message_add_tail(&t[1], &m);
110 
111 	mutex_lock(&at25->lock);
112 
113 	/* Read it all at once.
114 	 *
115 	 * REVISIT that's potentially a problem with large chips, if
116 	 * other devices on the bus need to be accessed regularly or
117 	 * this chip is clocked very slowly
118 	 */
119 	status = spi_sync(at25->spi, &m);
120 	dev_dbg(&at25->spi->dev,
121 		"read %Zd bytes at %d --> %d\n",
122 		count, offset, (int) status);
123 
124 	mutex_unlock(&at25->lock);
125 	return status ? status : count;
126 }
127 
128 static ssize_t
129 at25_bin_read(struct file *filp, struct kobject *kobj,
130 	      struct bin_attribute *bin_attr,
131 	      char *buf, loff_t off, size_t count)
132 {
133 	struct device		*dev;
134 	struct at25_data	*at25;
135 
136 	dev = container_of(kobj, struct device, kobj);
137 	at25 = dev_get_drvdata(dev);
138 
139 	return at25_ee_read(at25, buf, off, count);
140 }
141 
142 
143 static ssize_t
144 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off,
145 	      size_t count)
146 {
147 	ssize_t			status = 0;
148 	unsigned		written = 0;
149 	unsigned		buf_size;
150 	u8			*bounce;
151 
152 	if (unlikely(off >= at25->bin.size))
153 		return -EFBIG;
154 	if ((off + count) > at25->bin.size)
155 		count = at25->bin.size - off;
156 	if (unlikely(!count))
157 		return count;
158 
159 	/* Temp buffer starts with command and address */
160 	buf_size = at25->chip.page_size;
161 	if (buf_size > io_limit)
162 		buf_size = io_limit;
163 	bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
164 	if (!bounce)
165 		return -ENOMEM;
166 
167 	/* For write, rollover is within the page ... so we write at
168 	 * most one page, then manually roll over to the next page.
169 	 */
170 	bounce[0] = AT25_WRITE;
171 	mutex_lock(&at25->lock);
172 	do {
173 		unsigned long	timeout, retries;
174 		unsigned	segment;
175 		unsigned	offset = (unsigned) off;
176 		u8		*cp = bounce + 1;
177 		int		sr;
178 
179 		*cp = AT25_WREN;
180 		status = spi_write(at25->spi, cp, 1);
181 		if (status < 0) {
182 			dev_dbg(&at25->spi->dev, "WREN --> %d\n",
183 					(int) status);
184 			break;
185 		}
186 
187 		/* 8/16/24-bit address is written MSB first */
188 		switch (at25->addrlen) {
189 		default:	/* case 3 */
190 			*cp++ = offset >> 16;
191 		case 2:
192 			*cp++ = offset >> 8;
193 		case 1:
194 		case 0:	/* can't happen: for better codegen */
195 			*cp++ = offset >> 0;
196 		}
197 
198 		/* Write as much of a page as we can */
199 		segment = buf_size - (offset % buf_size);
200 		if (segment > count)
201 			segment = count;
202 		memcpy(cp, buf, segment);
203 		status = spi_write(at25->spi, bounce,
204 				segment + at25->addrlen + 1);
205 		dev_dbg(&at25->spi->dev,
206 				"write %u bytes at %u --> %d\n",
207 				segment, offset, (int) status);
208 		if (status < 0)
209 			break;
210 
211 		/* REVISIT this should detect (or prevent) failed writes
212 		 * to readonly sections of the EEPROM...
213 		 */
214 
215 		/* Wait for non-busy status */
216 		timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
217 		retries = 0;
218 		do {
219 
220 			sr = spi_w8r8(at25->spi, AT25_RDSR);
221 			if (sr < 0 || (sr & AT25_SR_nRDY)) {
222 				dev_dbg(&at25->spi->dev,
223 					"rdsr --> %d (%02x)\n", sr, sr);
224 				/* at HZ=100, this is sloooow */
225 				msleep(1);
226 				continue;
227 			}
228 			if (!(sr & AT25_SR_nRDY))
229 				break;
230 		} while (retries++ < 3 || time_before_eq(jiffies, timeout));
231 
232 		if ((sr < 0) || (sr & AT25_SR_nRDY)) {
233 			dev_err(&at25->spi->dev,
234 				"write %d bytes offset %d, "
235 				"timeout after %u msecs\n",
236 				segment, offset,
237 				jiffies_to_msecs(jiffies -
238 					(timeout - EE_TIMEOUT)));
239 			status = -ETIMEDOUT;
240 			break;
241 		}
242 
243 		off += segment;
244 		buf += segment;
245 		count -= segment;
246 		written += segment;
247 
248 	} while (count > 0);
249 
250 	mutex_unlock(&at25->lock);
251 
252 	kfree(bounce);
253 	return written ? written : status;
254 }
255 
256 static ssize_t
257 at25_bin_write(struct file *filp, struct kobject *kobj,
258 	       struct bin_attribute *bin_attr,
259 	       char *buf, loff_t off, size_t count)
260 {
261 	struct device		*dev;
262 	struct at25_data	*at25;
263 
264 	dev = container_of(kobj, struct device, kobj);
265 	at25 = dev_get_drvdata(dev);
266 
267 	return at25_ee_write(at25, buf, off, count);
268 }
269 
270 /*-------------------------------------------------------------------------*/
271 
272 /* Let in-kernel code access the eeprom data. */
273 
274 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf,
275 			 off_t offset, size_t count)
276 {
277 	struct at25_data *at25 = container_of(mem, struct at25_data, mem);
278 
279 	return at25_ee_read(at25, buf, offset, count);
280 }
281 
282 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf,
283 			  off_t offset, size_t count)
284 {
285 	struct at25_data *at25 = container_of(mem, struct at25_data, mem);
286 
287 	return at25_ee_write(at25, buf, offset, count);
288 }
289 
290 /*-------------------------------------------------------------------------*/
291 
292 static int at25_probe(struct spi_device *spi)
293 {
294 	struct at25_data	*at25 = NULL;
295 	const struct spi_eeprom *chip;
296 	int			err;
297 	int			sr;
298 	int			addrlen;
299 
300 	/* Chip description */
301 	chip = spi->dev.platform_data;
302 	if (!chip) {
303 		dev_dbg(&spi->dev, "no chip description\n");
304 		err = -ENODEV;
305 		goto fail;
306 	}
307 
308 	/* For now we only support 8/16/24 bit addressing */
309 	if (chip->flags & EE_ADDR1)
310 		addrlen = 1;
311 	else if (chip->flags & EE_ADDR2)
312 		addrlen = 2;
313 	else if (chip->flags & EE_ADDR3)
314 		addrlen = 3;
315 	else {
316 		dev_dbg(&spi->dev, "unsupported address type\n");
317 		err = -EINVAL;
318 		goto fail;
319 	}
320 
321 	/* Ping the chip ... the status register is pretty portable,
322 	 * unlike probing manufacturer IDs.  We do expect that system
323 	 * firmware didn't write it in the past few milliseconds!
324 	 */
325 	sr = spi_w8r8(spi, AT25_RDSR);
326 	if (sr < 0 || sr & AT25_SR_nRDY) {
327 		dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
328 		err = -ENXIO;
329 		goto fail;
330 	}
331 
332 	if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
333 		err = -ENOMEM;
334 		goto fail;
335 	}
336 
337 	mutex_init(&at25->lock);
338 	at25->chip = *chip;
339 	at25->spi = spi_dev_get(spi);
340 	dev_set_drvdata(&spi->dev, at25);
341 	at25->addrlen = addrlen;
342 
343 	/* Export the EEPROM bytes through sysfs, since that's convenient.
344 	 * And maybe to other kernel code; it might hold a board's Ethernet
345 	 * address, or board-specific calibration data generated on the
346 	 * manufacturing floor.
347 	 *
348 	 * Default to root-only access to the data; EEPROMs often hold data
349 	 * that's sensitive for read and/or write, like ethernet addresses,
350 	 * security codes, board-specific manufacturing calibrations, etc.
351 	 */
352 	sysfs_bin_attr_init(&at25->bin);
353 	at25->bin.attr.name = "eeprom";
354 	at25->bin.attr.mode = S_IRUSR;
355 	at25->bin.read = at25_bin_read;
356 	at25->mem.read = at25_mem_read;
357 
358 	at25->bin.size = at25->chip.byte_len;
359 	if (!(chip->flags & EE_READONLY)) {
360 		at25->bin.write = at25_bin_write;
361 		at25->bin.attr.mode |= S_IWUSR;
362 		at25->mem.write = at25_mem_write;
363 	}
364 
365 	err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
366 	if (err)
367 		goto fail;
368 
369 	if (chip->setup)
370 		chip->setup(&at25->mem, chip->context);
371 
372 	dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
373 		(at25->bin.size < 1024)
374 			? at25->bin.size
375 			: (at25->bin.size / 1024),
376 		(at25->bin.size < 1024) ? "Byte" : "KByte",
377 		at25->chip.name,
378 		(chip->flags & EE_READONLY) ? " (readonly)" : "",
379 		at25->chip.page_size);
380 	return 0;
381 fail:
382 	dev_dbg(&spi->dev, "probe err %d\n", err);
383 	kfree(at25);
384 	return err;
385 }
386 
387 static int __devexit at25_remove(struct spi_device *spi)
388 {
389 	struct at25_data	*at25;
390 
391 	at25 = dev_get_drvdata(&spi->dev);
392 	sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
393 	kfree(at25);
394 	return 0;
395 }
396 
397 /*-------------------------------------------------------------------------*/
398 
399 static struct spi_driver at25_driver = {
400 	.driver = {
401 		.name		= "at25",
402 		.owner		= THIS_MODULE,
403 	},
404 	.probe		= at25_probe,
405 	.remove		= __devexit_p(at25_remove),
406 };
407 
408 static int __init at25_init(void)
409 {
410 	return spi_register_driver(&at25_driver);
411 }
412 module_init(at25_init);
413 
414 static void __exit at25_exit(void)
415 {
416 	spi_unregister_driver(&at25_driver);
417 }
418 module_exit(at25_exit);
419 
420 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
421 MODULE_AUTHOR("David Brownell");
422 MODULE_LICENSE("GPL");
423 MODULE_ALIAS("spi:at25");
424