summaryrefslogtreecommitdiffstats
path: root/drivers/spi/at25.c
blob: 8efa07e8b8c2a7bef31ce118109b622e42de210d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
/*
 * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
 *
 * Copyright (C) 2006 David Brownell
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/sched.h>

#include <linux/spi/spi.h>
#include <linux/spi/eeprom.h>


struct at25_data {
	struct spi_device	*spi;
	struct mutex		lock;
	struct spi_eeprom	chip;
	struct bin_attribute	bin;
	unsigned		addrlen;
};

#define	AT25_WREN	0x06		/* latch the write enable */
#define	AT25_WRDI	0x04		/* reset the write enable */
#define	AT25_RDSR	0x05		/* read status register */
#define	AT25_WRSR	0x01		/* write status register */
#define	AT25_READ	0x03		/* read byte(s) */
#define	AT25_WRITE	0x02		/* write byte(s)/sector */

#define	AT25_SR_nRDY	0x01		/* nRDY = write-in-progress */
#define	AT25_SR_WEN	0x02		/* write enable (latched) */
#define	AT25_SR_BP0	0x04		/* BP for software writeprotect */
#define	AT25_SR_BP1	0x08
#define	AT25_SR_WPEN	0x80		/* writeprotect enable */


#define EE_MAXADDRLEN	3		/* 24 bit addresses, up to 2 MBytes */

/* Specs often allow 5 msec for a page write, sometimes 20 msec;
 * it's important to recover from write timeouts.
 */
#define	EE_TIMEOUT	25

/*-------------------------------------------------------------------------*/

#define	io_limit	PAGE_SIZE	/* bytes */

static ssize_t
at25_ee_read(
	struct at25_data	*at25,
	char			*buf,
	unsigned		offset,
	size_t			count
)
{
	u8			command[EE_MAXADDRLEN + 1];
	u8			*cp;
	ssize_t			status;
	struct spi_transfer	t[2];
	struct spi_message	m;

	cp = command;
	*cp++ = AT25_READ;

	/* 8/16/24-bit address is written MSB first */
	switch (at25->addrlen) {
	default:	/* case 3 */
		*cp++ = offset >> 16;
	case 2:
		*cp++ = offset >> 8;
	case 1:
	case 0:	/* can't happen: for better codegen */
		*cp++ = offset >> 0;
	}

	spi_message_init(&m);
	memset(t, 0, sizeof t);

	t[0].tx_buf = command;
	t[0].len = at25->addrlen + 1;
	spi_message_add_tail(&t[0], &m);

	t[1].rx_buf = buf;
	t[1].len = count;
	spi_message_add_tail(&t[1], &m);

	mutex_lock(&at25->lock);

	/* Read it all at once.
	 *
	 * REVISIT that's potentially a problem with large chips, if
	 * other devices on the bus need to be accessed regularly or
	 * this chip is clocked very slowly
	 */
	status = spi_sync(at25->spi, &m);
	dev_dbg(&at25->spi->dev,
		"read %Zd bytes at %d --> %d\n",
		count, offset, (int) status);

	mutex_unlock(&at25->lock);
	return status ? status : count;
}

static ssize_t
at25_bin_read(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	struct device		*dev;
	struct at25_data	*at25;

	dev = container_of(kobj, struct device, kobj);
	at25 = dev_get_drvdata(dev);

	if (unlikely(off >= at25->bin.size))
		return 0;
	if ((off + count) > at25->bin.size)
		count = at25->bin.size - off;
	if (unlikely(!count))
		return count;

	return at25_ee_read(at25, buf, off, count);
}


static ssize_t
at25_ee_write(struct at25_data *at25, char *buf, loff_t off, size_t count)
{
	ssize_t			status = 0;
	unsigned		written = 0;
	unsigned		buf_size;
	u8			*bounce;

	/* Temp buffer starts with command and address */
	buf_size = at25->chip.page_size;
	if (buf_size > io_limit)
		buf_size = io_limit;
	bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
	if (!bounce)
		return -ENOMEM;

	/* For write, rollover is within the page ... so we write at
	 * most one page, then manually roll over to the next page.
	 */
	bounce[0] = AT25_WRITE;
	mutex_lock(&at25->lock);
	do {
		unsigned long	timeout, retries;
		unsigned	segment;
		unsigned	offset = (unsigned) off;
		u8		*cp = bounce + 1;

		*cp = AT25_WREN;
		status = spi_write(at25->spi, cp, 1);
		if (status < 0) {
			dev_dbg(&at25->spi->dev, "WREN --> %d\n",
					(int) status);
			break;
		}

		/* 8/16/24-bit address is written MSB first */
		switch (at25->addrlen) {
		default:	/* case 3 */
			*cp++ = offset >> 16;
		case 2:
			*cp++ = offset >> 8;
		case 1:
		case 0:	/* can't happen: for better codegen */
			*cp++ = offset >> 0;
		}

		/* Write as much of a page as we can */
		segment = buf_size - (offset % buf_size);
		if (segment > count)
			segment = count;
		memcpy(cp, buf, segment);
		status = spi_write(at25->spi, bounce,
				segment + at25->addrlen + 1);
		dev_dbg(&at25->spi->dev,
				"write %u bytes at %u --> %d\n",
				segment, offset, (int) status);
		if (status < 0)
			break;

		/* REVISIT this should detect (or prevent) failed writes
		 * to readonly sections of the EEPROM...
		 */

		/* Wait for non-busy status */
		timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
		retries = 0;
		do {
			int	sr;

			sr = spi_w8r8(at25->spi, AT25_RDSR);
			if (sr < 0 || (sr & AT25_SR_nRDY)) {
				dev_dbg(&at25->spi->dev,
					"rdsr --> %d (%02x)\n", sr, sr);
				/* at HZ=100, this is sloooow */
				msleep(1);
				continue;
			}
			if (!(sr & AT25_SR_nRDY))
				break;
		} while (retries++ < 3 || time_before_eq(jiffies, timeout));

		if (time_after(jiffies, timeout)) {
			dev_err(&at25->spi->dev,
				"write %d bytes offset %d, "
				"timeout after %u msecs\n",
				segment, offset,
				jiffies_to_msecs(jiffies -
					(timeout - EE_TIMEOUT)));
			status = -ETIMEDOUT;
			break;
		}

		off += segment;
		buf += segment;
		count -= segment;
		written += segment;

	} while (count > 0);

	mutex_unlock(&at25->lock);

	kfree(bounce);
	return written ? written : status;
}

static ssize_t
at25_bin_write(struct kobject *kobj, char *buf, loff_t off, size_t count)
{
	struct device		*dev;
	struct at25_data	*at25;

	dev = container_of(kobj, struct device, kobj);
	at25 = dev_get_drvdata(dev);

	if (unlikely(off >= at25->bin.size))
		return -EFBIG;
	if ((off + count) > at25->bin.size)
		count = at25->bin.size - off;
	if (unlikely(!count))
		return count;

	return at25_ee_write(at25, buf, off, count);
}

/*-------------------------------------------------------------------------*/

static int at25_probe(struct spi_device *spi)
{
	struct at25_data	*at25 = NULL;
	const struct spi_eeprom *chip;
	int			err;
	int			sr;
	int			addrlen;

	/* Chip description */
	chip = spi->dev.platform_data;
	if (!chip) {
		dev_dbg(&spi->dev, "no chip description\n");
		err = -ENODEV;
		goto fail;
	}

	/* For now we only support 8/16/24 bit addressing */
	if (chip->flags & EE_ADDR1)
		addrlen = 1;
	else if (chip->flags & EE_ADDR2)
		addrlen = 2;
	else if (chip->flags & EE_ADDR3)
		addrlen = 3;
	else {
		dev_dbg(&spi->dev, "unsupported address type\n");
		err = -EINVAL;
		goto fail;
	}

	/* Ping the chip ... the status register is pretty portable,
	 * unlike probing manufacturer IDs.  We do expect that system
	 * firmware didn't write it in the past few milliseconds!
	 */
	sr = spi_w8r8(spi, AT25_RDSR);
	if (sr < 0 || sr & AT25_SR_nRDY) {
		dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr);
		err = -ENXIO;
		goto fail;
	}

	if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
		err = -ENOMEM;
		goto fail;
	}

	mutex_init(&at25->lock);
	at25->chip = *chip;
	at25->spi = spi_dev_get(spi);
	dev_set_drvdata(&spi->dev, at25);
	at25->addrlen = addrlen;

	/* Export the EEPROM bytes through sysfs, since that's convenient.
	 * Default to root-only access to the data; EEPROMs often hold data
	 * that's sensitive for read and/or write, like ethernet addresses,
	 * security codes, board-specific manufacturing calibrations, etc.
	 */
	at25->bin.attr.name = "eeprom";
	at25->bin.attr.mode = S_IRUSR;
	at25->bin.attr.owner = THIS_MODULE;
	at25->bin.read = at25_bin_read;

	at25->bin.size = at25->chip.byte_len;
	if (!(chip->flags & EE_READONLY)) {
		at25->bin.write = at25_bin_write;
		at25->bin.attr.mode |= S_IWUSR;
	}

	err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
	if (err)
		goto fail;

	dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
		(at25->bin.size < 1024)
			? at25->bin.size
			: (at25->bin.size / 1024),
		(at25->bin.size < 1024) ? "Byte" : "KByte",
		at25->chip.name,
		(chip->flags & EE_READONLY) ? " (readonly)" : "",
		at25->chip.page_size);
	return 0;
fail:
	dev_dbg(&spi->dev, "probe err %d\n", err);
	kfree(at25);
	return err;
}

static int __devexit at25_remove(struct spi_device *spi)
{
	struct at25_data	*at25;

	at25 = dev_get_drvdata(&spi->dev);
	sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
	kfree(at25);
	return 0;
}

/*-------------------------------------------------------------------------*/

static struct spi_driver at25_driver = {
	.driver = {
		.name		= "at25",
		.owner		= THIS_MODULE,
	},
	.probe		= at25_probe,
	.remove		= __devexit_p(at25_remove),
};

static int __init at25_init(void)
{
	return spi_register_driver(&at25_driver);
}
module_init(at25_init);

static void __exit at25_exit(void)
{
	spi_unregister_driver(&at25_driver);
}
module_exit(at25_exit);

MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
MODULE_AUTHOR("David Brownell");
MODULE_LICENSE("GPL");

OpenPOWER on IntegriCloud