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/module.h> 14 #include <linux/slab.h> 15 #include <linux/delay.h> 16 #include <linux/device.h> 17 #include <linux/sched.h> 18 19 #include <linux/spi/spi.h> 20 #include <linux/spi/eeprom.h> 21 #include <linux/of.h> 22 23 /* 24 * NOTE: this is an *EEPROM* driver. The vagaries of product naming 25 * mean that some AT25 products are EEPROMs, and others are FLASH. 26 * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver, 27 * not this one! 28 */ 29 30 struct at25_data { 31 struct spi_device *spi; 32 struct memory_accessor mem; 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 #define AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */ 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 u8 instr; 79 80 if (unlikely(offset >= at25->bin.size)) 81 return 0; 82 if ((offset + count) > at25->bin.size) 83 count = at25->bin.size - offset; 84 if (unlikely(!count)) 85 return count; 86 87 cp = command; 88 89 instr = AT25_READ; 90 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 91 if (offset >= (1U << (at25->addrlen * 8))) 92 instr |= AT25_INSTR_BIT3; 93 *cp++ = instr; 94 95 /* 8/16/24-bit address is written MSB first */ 96 switch (at25->addrlen) { 97 default: /* case 3 */ 98 *cp++ = offset >> 16; 99 case 2: 100 *cp++ = offset >> 8; 101 case 1: 102 case 0: /* can't happen: for better codegen */ 103 *cp++ = offset >> 0; 104 } 105 106 spi_message_init(&m); 107 memset(t, 0, sizeof t); 108 109 t[0].tx_buf = command; 110 t[0].len = at25->addrlen + 1; 111 spi_message_add_tail(&t[0], &m); 112 113 t[1].rx_buf = buf; 114 t[1].len = count; 115 spi_message_add_tail(&t[1], &m); 116 117 mutex_lock(&at25->lock); 118 119 /* Read it all at once. 120 * 121 * REVISIT that's potentially a problem with large chips, if 122 * other devices on the bus need to be accessed regularly or 123 * this chip is clocked very slowly 124 */ 125 status = spi_sync(at25->spi, &m); 126 dev_dbg(&at25->spi->dev, 127 "read %Zd bytes at %d --> %d\n", 128 count, offset, (int) status); 129 130 mutex_unlock(&at25->lock); 131 return status ? status : count; 132 } 133 134 static ssize_t 135 at25_bin_read(struct file *filp, struct kobject *kobj, 136 struct bin_attribute *bin_attr, 137 char *buf, loff_t off, size_t count) 138 { 139 struct device *dev; 140 struct at25_data *at25; 141 142 dev = container_of(kobj, struct device, kobj); 143 at25 = dev_get_drvdata(dev); 144 145 return at25_ee_read(at25, buf, off, count); 146 } 147 148 149 static ssize_t 150 at25_ee_write(struct at25_data *at25, const char *buf, loff_t off, 151 size_t count) 152 { 153 ssize_t status = 0; 154 unsigned written = 0; 155 unsigned buf_size; 156 u8 *bounce; 157 158 if (unlikely(off >= at25->bin.size)) 159 return -EFBIG; 160 if ((off + count) > at25->bin.size) 161 count = at25->bin.size - off; 162 if (unlikely(!count)) 163 return count; 164 165 /* Temp buffer starts with command and address */ 166 buf_size = at25->chip.page_size; 167 if (buf_size > io_limit) 168 buf_size = io_limit; 169 bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL); 170 if (!bounce) 171 return -ENOMEM; 172 173 /* For write, rollover is within the page ... so we write at 174 * most one page, then manually roll over to the next page. 175 */ 176 mutex_lock(&at25->lock); 177 do { 178 unsigned long timeout, retries; 179 unsigned segment; 180 unsigned offset = (unsigned) off; 181 u8 *cp = bounce; 182 int sr; 183 u8 instr; 184 185 *cp = AT25_WREN; 186 status = spi_write(at25->spi, cp, 1); 187 if (status < 0) { 188 dev_dbg(&at25->spi->dev, "WREN --> %d\n", 189 (int) status); 190 break; 191 } 192 193 instr = AT25_WRITE; 194 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 195 if (offset >= (1U << (at25->addrlen * 8))) 196 instr |= AT25_INSTR_BIT3; 197 *cp++ = instr; 198 199 /* 8/16/24-bit address is written MSB first */ 200 switch (at25->addrlen) { 201 default: /* case 3 */ 202 *cp++ = offset >> 16; 203 case 2: 204 *cp++ = offset >> 8; 205 case 1: 206 case 0: /* can't happen: for better codegen */ 207 *cp++ = offset >> 0; 208 } 209 210 /* Write as much of a page as we can */ 211 segment = buf_size - (offset % buf_size); 212 if (segment > count) 213 segment = count; 214 memcpy(cp, buf, segment); 215 status = spi_write(at25->spi, bounce, 216 segment + at25->addrlen + 1); 217 dev_dbg(&at25->spi->dev, 218 "write %u bytes at %u --> %d\n", 219 segment, offset, (int) status); 220 if (status < 0) 221 break; 222 223 /* REVISIT this should detect (or prevent) failed writes 224 * to readonly sections of the EEPROM... 225 */ 226 227 /* Wait for non-busy status */ 228 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT); 229 retries = 0; 230 do { 231 232 sr = spi_w8r8(at25->spi, AT25_RDSR); 233 if (sr < 0 || (sr & AT25_SR_nRDY)) { 234 dev_dbg(&at25->spi->dev, 235 "rdsr --> %d (%02x)\n", sr, sr); 236 /* at HZ=100, this is sloooow */ 237 msleep(1); 238 continue; 239 } 240 if (!(sr & AT25_SR_nRDY)) 241 break; 242 } while (retries++ < 3 || time_before_eq(jiffies, timeout)); 243 244 if ((sr < 0) || (sr & AT25_SR_nRDY)) { 245 dev_err(&at25->spi->dev, 246 "write %d bytes offset %d, " 247 "timeout after %u msecs\n", 248 segment, offset, 249 jiffies_to_msecs(jiffies - 250 (timeout - EE_TIMEOUT))); 251 status = -ETIMEDOUT; 252 break; 253 } 254 255 off += segment; 256 buf += segment; 257 count -= segment; 258 written += segment; 259 260 } while (count > 0); 261 262 mutex_unlock(&at25->lock); 263 264 kfree(bounce); 265 return written ? written : status; 266 } 267 268 static ssize_t 269 at25_bin_write(struct file *filp, struct kobject *kobj, 270 struct bin_attribute *bin_attr, 271 char *buf, loff_t off, size_t count) 272 { 273 struct device *dev; 274 struct at25_data *at25; 275 276 dev = container_of(kobj, struct device, kobj); 277 at25 = dev_get_drvdata(dev); 278 279 return at25_ee_write(at25, buf, off, count); 280 } 281 282 /*-------------------------------------------------------------------------*/ 283 284 /* Let in-kernel code access the eeprom data. */ 285 286 static ssize_t at25_mem_read(struct memory_accessor *mem, char *buf, 287 off_t offset, size_t count) 288 { 289 struct at25_data *at25 = container_of(mem, struct at25_data, mem); 290 291 return at25_ee_read(at25, buf, offset, count); 292 } 293 294 static ssize_t at25_mem_write(struct memory_accessor *mem, const char *buf, 295 off_t offset, size_t count) 296 { 297 struct at25_data *at25 = container_of(mem, struct at25_data, mem); 298 299 return at25_ee_write(at25, buf, offset, count); 300 } 301 302 /*-------------------------------------------------------------------------*/ 303 304 static int at25_np_to_chip(struct device *dev, 305 struct device_node *np, 306 struct spi_eeprom *chip) 307 { 308 u32 val; 309 310 memset(chip, 0, sizeof(*chip)); 311 strncpy(chip->name, np->name, sizeof(chip->name)); 312 313 if (of_property_read_u32(np, "size", &val) == 0 || 314 of_property_read_u32(np, "at25,byte-len", &val) == 0) { 315 chip->byte_len = val; 316 } else { 317 dev_err(dev, "Error: missing \"size\" property\n"); 318 return -ENODEV; 319 } 320 321 if (of_property_read_u32(np, "pagesize", &val) == 0 || 322 of_property_read_u32(np, "at25,page-size", &val) == 0) { 323 chip->page_size = (u16)val; 324 } else { 325 dev_err(dev, "Error: missing \"pagesize\" property\n"); 326 return -ENODEV; 327 } 328 329 if (of_property_read_u32(np, "at25,addr-mode", &val) == 0) { 330 chip->flags = (u16)val; 331 } else { 332 if (of_property_read_u32(np, "address-width", &val)) { 333 dev_err(dev, 334 "Error: missing \"address-width\" property\n"); 335 return -ENODEV; 336 } 337 switch (val) { 338 case 8: 339 chip->flags |= EE_ADDR1; 340 break; 341 case 16: 342 chip->flags |= EE_ADDR2; 343 break; 344 case 24: 345 chip->flags |= EE_ADDR3; 346 break; 347 default: 348 dev_err(dev, 349 "Error: bad \"address-width\" property: %u\n", 350 val); 351 return -ENODEV; 352 } 353 if (of_find_property(np, "read-only", NULL)) 354 chip->flags |= EE_READONLY; 355 } 356 return 0; 357 } 358 359 static int at25_probe(struct spi_device *spi) 360 { 361 struct at25_data *at25 = NULL; 362 struct spi_eeprom chip; 363 struct device_node *np = spi->dev.of_node; 364 int err; 365 int sr; 366 int addrlen; 367 368 /* Chip description */ 369 if (!spi->dev.platform_data) { 370 if (np) { 371 err = at25_np_to_chip(&spi->dev, np, &chip); 372 if (err) 373 return err; 374 } else { 375 dev_err(&spi->dev, "Error: no chip description\n"); 376 return -ENODEV; 377 } 378 } else 379 chip = *(struct spi_eeprom *)spi->dev.platform_data; 380 381 /* For now we only support 8/16/24 bit addressing */ 382 if (chip.flags & EE_ADDR1) 383 addrlen = 1; 384 else if (chip.flags & EE_ADDR2) 385 addrlen = 2; 386 else if (chip.flags & EE_ADDR3) 387 addrlen = 3; 388 else { 389 dev_dbg(&spi->dev, "unsupported address type\n"); 390 return -EINVAL; 391 } 392 393 /* Ping the chip ... the status register is pretty portable, 394 * unlike probing manufacturer IDs. We do expect that system 395 * firmware didn't write it in the past few milliseconds! 396 */ 397 sr = spi_w8r8(spi, AT25_RDSR); 398 if (sr < 0 || sr & AT25_SR_nRDY) { 399 dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr); 400 return -ENXIO; 401 } 402 403 at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL); 404 if (!at25) 405 return -ENOMEM; 406 407 mutex_init(&at25->lock); 408 at25->chip = chip; 409 at25->spi = spi_dev_get(spi); 410 spi_set_drvdata(spi, at25); 411 at25->addrlen = addrlen; 412 413 /* Export the EEPROM bytes through sysfs, since that's convenient. 414 * And maybe to other kernel code; it might hold a board's Ethernet 415 * address, or board-specific calibration data generated on the 416 * manufacturing floor. 417 * 418 * Default to root-only access to the data; EEPROMs often hold data 419 * that's sensitive for read and/or write, like ethernet addresses, 420 * security codes, board-specific manufacturing calibrations, etc. 421 */ 422 sysfs_bin_attr_init(&at25->bin); 423 at25->bin.attr.name = "eeprom"; 424 at25->bin.attr.mode = S_IRUSR; 425 at25->bin.read = at25_bin_read; 426 at25->mem.read = at25_mem_read; 427 428 at25->bin.size = at25->chip.byte_len; 429 if (!(chip.flags & EE_READONLY)) { 430 at25->bin.write = at25_bin_write; 431 at25->bin.attr.mode |= S_IWUSR; 432 at25->mem.write = at25_mem_write; 433 } 434 435 err = sysfs_create_bin_file(&spi->dev.kobj, &at25->bin); 436 if (err) 437 return err; 438 439 if (chip.setup) 440 chip.setup(&at25->mem, chip.context); 441 442 dev_info(&spi->dev, "%Zd %s %s eeprom%s, pagesize %u\n", 443 (at25->bin.size < 1024) 444 ? at25->bin.size 445 : (at25->bin.size / 1024), 446 (at25->bin.size < 1024) ? "Byte" : "KByte", 447 at25->chip.name, 448 (chip.flags & EE_READONLY) ? " (readonly)" : "", 449 at25->chip.page_size); 450 return 0; 451 } 452 453 static int at25_remove(struct spi_device *spi) 454 { 455 struct at25_data *at25; 456 457 at25 = spi_get_drvdata(spi); 458 sysfs_remove_bin_file(&spi->dev.kobj, &at25->bin); 459 return 0; 460 } 461 462 /*-------------------------------------------------------------------------*/ 463 464 static const struct of_device_id at25_of_match[] = { 465 { .compatible = "atmel,at25", }, 466 { } 467 }; 468 MODULE_DEVICE_TABLE(of, at25_of_match); 469 470 static struct spi_driver at25_driver = { 471 .driver = { 472 .name = "at25", 473 .owner = THIS_MODULE, 474 .of_match_table = at25_of_match, 475 }, 476 .probe = at25_probe, 477 .remove = at25_remove, 478 }; 479 480 module_spi_driver(at25_driver); 481 482 MODULE_DESCRIPTION("Driver for most SPI EEPROMs"); 483 MODULE_AUTHOR("David Brownell"); 484 MODULE_LICENSE("GPL"); 485 MODULE_ALIAS("spi:at25"); 486