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