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 #define AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */ 54 55 #define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */ 56 57 /* Specs often allow 5 msec for a page write, sometimes 20 msec; 58 * it's important to recover from write timeouts. 59 */ 60 #define EE_TIMEOUT 25 61 62 /*-------------------------------------------------------------------------*/ 63 64 #define io_limit PAGE_SIZE /* bytes */ 65 66 static ssize_t 67 at25_ee_read( 68 struct at25_data *at25, 69 char *buf, 70 unsigned offset, 71 size_t count 72 ) 73 { 74 u8 command[EE_MAXADDRLEN + 1]; 75 u8 *cp; 76 ssize_t status; 77 struct spi_transfer t[2]; 78 struct spi_message m; 79 u8 instr; 80 81 if (unlikely(offset >= at25->bin.size)) 82 return 0; 83 if ((offset + count) > at25->bin.size) 84 count = at25->bin.size - offset; 85 if (unlikely(!count)) 86 return count; 87 88 cp = command; 89 90 instr = AT25_READ; 91 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 92 if (offset >= (1U << (at25->addrlen * 8))) 93 instr |= AT25_INSTR_BIT3; 94 *cp++ = instr; 95 96 /* 8/16/24-bit address is written MSB first */ 97 switch (at25->addrlen) { 98 default: /* case 3 */ 99 *cp++ = offset >> 16; 100 case 2: 101 *cp++ = offset >> 8; 102 case 1: 103 case 0: /* can't happen: for better codegen */ 104 *cp++ = offset >> 0; 105 } 106 107 spi_message_init(&m); 108 memset(t, 0, sizeof t); 109 110 t[0].tx_buf = command; 111 t[0].len = at25->addrlen + 1; 112 spi_message_add_tail(&t[0], &m); 113 114 t[1].rx_buf = buf; 115 t[1].len = count; 116 spi_message_add_tail(&t[1], &m); 117 118 mutex_lock(&at25->lock); 119 120 /* Read it all at once. 121 * 122 * REVISIT that's potentially a problem with large chips, if 123 * other devices on the bus need to be accessed regularly or 124 * this chip is clocked very slowly 125 */ 126 status = spi_sync(at25->spi, &m); 127 dev_dbg(&at25->spi->dev, 128 "read %Zd bytes at %d --> %d\n", 129 count, offset, (int) status); 130 131 mutex_unlock(&at25->lock); 132 return status ? status : count; 133 } 134 135 static ssize_t 136 at25_bin_read(struct file *filp, struct kobject *kobj, 137 struct bin_attribute *bin_attr, 138 char *buf, loff_t off, size_t count) 139 { 140 struct device *dev; 141 struct at25_data *at25; 142 143 dev = container_of(kobj, struct device, kobj); 144 at25 = dev_get_drvdata(dev); 145 146 return at25_ee_read(at25, buf, off, count); 147 } 148 149 150 static ssize_t 151 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off, 152 size_t count) 153 { 154 ssize_t status = 0; 155 unsigned written = 0; 156 unsigned buf_size; 157 u8 *bounce; 158 159 if (unlikely(off >= at25->bin.size)) 160 return -EFBIG; 161 if ((off + count) > at25->bin.size) 162 count = at25->bin.size - off; 163 if (unlikely(!count)) 164 return count; 165 166 /* Temp buffer starts with command and address */ 167 buf_size = at25->chip.page_size; 168 if (buf_size > io_limit) 169 buf_size = io_limit; 170 bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL); 171 if (!bounce) 172 return -ENOMEM; 173 174 /* For write, rollover is within the page ... so we write at 175 * most one page, then manually roll over to the next page. 176 */ 177 mutex_lock(&at25->lock); 178 do { 179 unsigned long timeout, retries; 180 unsigned segment; 181 unsigned offset = (unsigned) off; 182 u8 *cp = bounce; 183 int sr; 184 u8 instr; 185 186 *cp = AT25_WREN; 187 status = spi_write(at25->spi, cp, 1); 188 if (status < 0) { 189 dev_dbg(&at25->spi->dev, "WREN --> %d\n", 190 (int) status); 191 break; 192 } 193 194 instr = AT25_WRITE; 195 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 196 if (offset >= (1U << (at25->addrlen * 8))) 197 instr |= AT25_INSTR_BIT3; 198 *cp++ = instr; 199 200 /* 8/16/24-bit address is written MSB first */ 201 switch (at25->addrlen) { 202 default: /* case 3 */ 203 *cp++ = offset >> 16; 204 case 2: 205 *cp++ = offset >> 8; 206 case 1: 207 case 0: /* can't happen: for better codegen */ 208 *cp++ = offset >> 0; 209 } 210 211 /* Write as much of a page as we can */ 212 segment = buf_size - (offset % buf_size); 213 if (segment > count) 214 segment = count; 215 memcpy(cp, buf, segment); 216 status = spi_write(at25->spi, bounce, 217 segment + at25->addrlen + 1); 218 dev_dbg(&at25->spi->dev, 219 "write %u bytes at %u --> %d\n", 220 segment, offset, (int) status); 221 if (status < 0) 222 break; 223 224 /* REVISIT this should detect (or prevent) failed writes 225 * to readonly sections of the EEPROM... 226 */ 227 228 /* Wait for non-busy status */ 229 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT); 230 retries = 0; 231 do { 232 233 sr = spi_w8r8(at25->spi, AT25_RDSR); 234 if (sr < 0 || (sr & AT25_SR_nRDY)) { 235 dev_dbg(&at25->spi->dev, 236 "rdsr --> %d (%02x)\n", sr, sr); 237 /* at HZ=100, this is sloooow */ 238 msleep(1); 239 continue; 240 } 241 if (!(sr & AT25_SR_nRDY)) 242 break; 243 } while (retries++ < 3 || time_before_eq(jiffies, timeout)); 244 245 if ((sr < 0) || (sr & AT25_SR_nRDY)) { 246 dev_err(&at25->spi->dev, 247 "write %d bytes offset %d, " 248 "timeout after %u msecs\n", 249 segment, offset, 250 jiffies_to_msecs(jiffies - 251 (timeout - EE_TIMEOUT))); 252 status = -ETIMEDOUT; 253 break; 254 } 255 256 off += segment; 257 buf += segment; 258 count -= segment; 259 written += segment; 260 261 } while (count > 0); 262 263 mutex_unlock(&at25->lock); 264 265 kfree(bounce); 266 return written ? written : status; 267 } 268 269 static ssize_t 270 at25_bin_write(struct file *filp, struct kobject *kobj, 271 struct bin_attribute *bin_attr, 272 char *buf, loff_t off, size_t count) 273 { 274 struct device *dev; 275 struct at25_data *at25; 276 277 dev = container_of(kobj, struct device, kobj); 278 at25 = dev_get_drvdata(dev); 279 280 return at25_ee_write(at25, buf, off, count); 281 } 282 283 /*-------------------------------------------------------------------------*/ 284 285 /* Let in-kernel code access the eeprom data. */ 286 287 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf, 288 off_t offset, size_t count) 289 { 290 struct at25_data *at25 = container_of(mem, struct at25_data, mem); 291 292 return at25_ee_read(at25, buf, offset, count); 293 } 294 295 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf, 296 off_t offset, size_t count) 297 { 298 struct at25_data *at25 = container_of(mem, struct at25_data, mem); 299 300 return at25_ee_write(at25, buf, offset, count); 301 } 302 303 /*-------------------------------------------------------------------------*/ 304 305 static int at25_probe(struct spi_device *spi) 306 { 307 struct at25_data *at25 = NULL; 308 const struct spi_eeprom *chip; 309 int err; 310 int sr; 311 int addrlen; 312 313 /* Chip description */ 314 chip = spi->dev.platform_data; 315 if (!chip) { 316 dev_dbg(&spi->dev, "no chip description\n"); 317 err = -ENODEV; 318 goto fail; 319 } 320 321 /* For now we only support 8/16/24 bit addressing */ 322 if (chip->flags & EE_ADDR1) 323 addrlen = 1; 324 else if (chip->flags & EE_ADDR2) 325 addrlen = 2; 326 else if (chip->flags & EE_ADDR3) 327 addrlen = 3; 328 else { 329 dev_dbg(&spi->dev, "unsupported address type\n"); 330 err = -EINVAL; 331 goto fail; 332 } 333 334 /* Ping the chip ... the status register is pretty portable, 335 * unlike probing manufacturer IDs. We do expect that system 336 * firmware didn't write it in the past few milliseconds! 337 */ 338 sr = spi_w8r8(spi, AT25_RDSR); 339 if (sr < 0 || sr & AT25_SR_nRDY) { 340 dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr); 341 err = -ENXIO; 342 goto fail; 343 } 344 345 if (!(at25 = kzalloc(sizeof *at25, GFP_KERNEL))) { 346 err = -ENOMEM; 347 goto fail; 348 } 349 350 mutex_init(&at25->lock); 351 at25->chip = *chip; 352 at25->spi = spi_dev_get(spi); 353 dev_set_drvdata(&spi->dev, at25); 354 at25->addrlen = addrlen; 355 356 /* Export the EEPROM bytes through sysfs, since that's convenient. 357 * And maybe to other kernel code; it might hold a board's Ethernet 358 * address, or board-specific calibration data generated on the 359 * manufacturing floor. 360 * 361 * Default to root-only access to the data; EEPROMs often hold data 362 * that's sensitive for read and/or write, like ethernet addresses, 363 * security codes, board-specific manufacturing calibrations, etc. 364 */ 365 sysfs_bin_attr_init(&at25->bin); 366 at25->bin.attr.name = "eeprom"; 367 at25->bin.attr.mode = S_IRUSR; 368 at25->bin.read = at25_bin_read; 369 at25->mem.read = at25_mem_read; 370 371 at25->bin.size = at25->chip.byte_len; 372 if (!(chip->flags & EE_READONLY)) { 373 at25->bin.write = at25_bin_write; 374 at25->bin.attr.mode |= S_IWUSR; 375 at25->mem.write = at25_mem_write; 376 } 377 378 err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin); 379 if (err) 380 goto fail; 381 382 if (chip->setup) 383 chip->setup(&at25->mem, chip->context); 384 385 dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n", 386 (at25->bin.size < 1024) 387 ? at25->bin.size 388 : (at25->bin.size / 1024), 389 (at25->bin.size < 1024) ? "Byte" : "KByte", 390 at25->chip.name, 391 (chip->flags & EE_READONLY) ? " (readonly)" : "", 392 at25->chip.page_size); 393 return 0; 394 fail: 395 dev_dbg(&spi->dev, "probe err %d\n", err); 396 kfree(at25); 397 return err; 398 } 399 400 static int __devexit at25_remove(struct spi_device *spi) 401 { 402 struct at25_data *at25; 403 404 at25 = dev_get_drvdata(&spi->dev); 405 sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin); 406 kfree(at25); 407 return 0; 408 } 409 410 /*-------------------------------------------------------------------------*/ 411 412 static struct spi_driver at25_driver = { 413 .driver = { 414 .name = "at25", 415 .owner = THIS_MODULE, 416 }, 417 .probe = at25_probe, 418 .remove = __devexit_p(at25_remove), 419 }; 420 421 module_spi_driver(at25_driver); 422 423 MODULE_DESCRIPTION("Driver for most SPI EEPROMs"); 424 MODULE_AUTHOR("David Brownell"); 425 MODULE_LICENSE("GPL"); 426 MODULE_ALIAS("spi:at25"); 427