2 * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models
4 * Copyright (C) 2006 David Brownell
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.
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>
20 #include <linux/spi/spi.h>
21 #include <linux/spi/eeprom.h>
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,
32 struct spi_device *spi;
33 struct memory_accessor mem;
35 struct spi_eeprom chip;
36 struct bin_attribute bin;
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 */
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 */
54 #define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */
56 /* Specs often allow 5 msec for a page write, sometimes 20 msec;
57 * it's important to recover from write timeouts.
61 /*-------------------------------------------------------------------------*/
63 #define io_limit PAGE_SIZE /* bytes */
67 struct at25_data *at25,
73 u8 command[EE_MAXADDRLEN + 1];
76 struct spi_transfer t[2];
79 if (unlikely(offset >= at25->bin.size))
81 if ((offset + count) > at25->bin.size)
82 count = at25->bin.size - offset;
89 /* 8/16/24-bit address is written MSB first */
90 switch (at25->addrlen) {
96 case 0: /* can't happen: for better codegen */
100 spi_message_init(&m);
101 memset(t, 0, sizeof t);
103 t[0].tx_buf = command;
104 t[0].len = at25->addrlen + 1;
105 spi_message_add_tail(&t[0], &m);
109 spi_message_add_tail(&t[1], &m);
111 mutex_lock(&at25->lock);
113 /* Read it all at once.
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
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);
124 mutex_unlock(&at25->lock);
125 return status ? status : count;
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)
134 struct at25_data *at25;
136 dev = container_of(kobj, struct device, kobj);
137 at25 = dev_get_drvdata(dev);
139 return at25_ee_read(at25, buf, off, count);
144 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off,
148 unsigned written = 0;
152 if (unlikely(off >= at25->bin.size))
154 if ((off + count) > at25->bin.size)
155 count = at25->bin.size - off;
156 if (unlikely(!count))
159 /* Temp buffer starts with command and address */
160 buf_size = at25->chip.page_size;
161 if (buf_size > io_limit)
163 bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL);
167 /* For write, rollover is within the page ... so we write at
168 * most one page, then manually roll over to the next page.
170 bounce[0] = AT25_WRITE;
171 mutex_lock(&at25->lock);
173 unsigned long timeout, retries;
175 unsigned offset = (unsigned) off;
180 status = spi_write(at25->spi, cp, 1);
182 dev_dbg(&at25->spi->dev, "WREN --> %d\n",
187 /* 8/16/24-bit address is written MSB first */
188 switch (at25->addrlen) {
189 default: /* case 3 */
190 *cp++ = offset >> 16;
194 case 0: /* can't happen: for better codegen */
198 /* Write as much of a page as we can */
199 segment = buf_size - (offset % buf_size);
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);
211 /* REVISIT this should detect (or prevent) failed writes
212 * to readonly sections of the EEPROM...
215 /* Wait for non-busy status */
216 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT);
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 */
228 if (!(sr & AT25_SR_nRDY))
230 } while (retries++ < 3 || time_before_eq(jiffies, timeout));
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",
237 jiffies_to_msecs(jiffies -
238 (timeout - EE_TIMEOUT)));
250 mutex_unlock(&at25->lock);
253 return written ? written : status;
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)
262 struct at25_data *at25;
264 dev = container_of(kobj, struct device, kobj);
265 at25 = dev_get_drvdata(dev);
267 return at25_ee_write(at25, buf, off, count);
270 /*-------------------------------------------------------------------------*/
272 /* Let in-kernel code access the eeprom data. */
274 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf,
275 off_t offset, size_t count)
277 struct at25_data *at25 = container_of(mem, struct at25_data, mem);
279 return at25_ee_read(at25, buf, offset, count);
282 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf,
283 off_t offset, size_t count)
285 struct at25_data *at25 = container_of(mem, struct at25_data, mem);
287 return at25_ee_write(at25, buf, offset, count);
290 /*-------------------------------------------------------------------------*/
292 static int at25_probe(struct spi_device *spi)
294 struct at25_data *at25 = NULL;
295 const struct spi_eeprom *chip;
300 /* Chip description */
301 chip = spi->dev.platform_data;
303 dev_dbg(&spi->dev, "no chip description\n");
308 /* For now we only support 8/16/24 bit addressing */
309 if (chip->flags & EE_ADDR1)
311 else if (chip->flags & EE_ADDR2)
313 else if (chip->flags & EE_ADDR3)
316 dev_dbg(&spi->dev, "unsupported address type\n");
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!
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);
332 if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) {
337 mutex_init(&at25->lock);
339 at25->spi = spi_dev_get(spi);
340 dev_set_drvdata(&spi->dev, at25);
341 at25->addrlen = addrlen;
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.
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.
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;
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;
365 err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin);
370 chip->setup(&at25->mem, chip->context);
372 dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n",
373 (at25->bin.size < 1024)
375 : (at25->bin.size / 1024),
376 (at25->bin.size < 1024) ? "Byte" : "KByte",
378 (chip->flags & EE_READONLY) ? " (readonly)" : "",
379 at25->chip.page_size);
382 dev_dbg(&spi->dev, "probe err %d\n", err);
387 static int __devexit at25_remove(struct spi_device *spi)
389 struct at25_data *at25;
391 at25 = dev_get_drvdata(&spi->dev);
392 sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin);
397 /*-------------------------------------------------------------------------*/
399 static struct spi_driver at25_driver = {
402 .owner = THIS_MODULE,
405 .remove = __devexit_p(at25_remove),
408 module_spi_driver(at25_driver);
410 MODULE_DESCRIPTION("Driver for most SPI EEPROMs");
411 MODULE_AUTHOR("David Brownell");
412 MODULE_LICENSE("GPL");
413 MODULE_ALIAS("spi:at25");