1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * at25.c -- support most SPI EEPROMs, such as Atmel AT25 models 4 * 5 * Copyright (C) 2006 David Brownell 6 */ 7 8 #include <linux/kernel.h> 9 #include <linux/module.h> 10 #include <linux/slab.h> 11 #include <linux/delay.h> 12 #include <linux/device.h> 13 #include <linux/sched.h> 14 15 #include <linux/nvmem-provider.h> 16 #include <linux/spi/spi.h> 17 #include <linux/spi/eeprom.h> 18 #include <linux/property.h> 19 20 /* 21 * NOTE: this is an *EEPROM* driver. The vagaries of product naming 22 * mean that some AT25 products are EEPROMs, and others are FLASH. 23 * Handle FLASH chips with the drivers/mtd/devices/m25p80.c driver, 24 * not this one! 25 */ 26 27 struct at25_data { 28 struct spi_device *spi; 29 struct mutex lock; 30 struct spi_eeprom chip; 31 unsigned addrlen; 32 struct nvmem_config nvmem_config; 33 struct nvmem_device *nvmem; 34 }; 35 36 #define AT25_WREN 0x06 /* latch the write enable */ 37 #define AT25_WRDI 0x04 /* reset the write enable */ 38 #define AT25_RDSR 0x05 /* read status register */ 39 #define AT25_WRSR 0x01 /* write status register */ 40 #define AT25_READ 0x03 /* read byte(s) */ 41 #define AT25_WRITE 0x02 /* write byte(s)/sector */ 42 43 #define AT25_SR_nRDY 0x01 /* nRDY = write-in-progress */ 44 #define AT25_SR_WEN 0x02 /* write enable (latched) */ 45 #define AT25_SR_BP0 0x04 /* BP for software writeprotect */ 46 #define AT25_SR_BP1 0x08 47 #define AT25_SR_WPEN 0x80 /* writeprotect enable */ 48 49 #define AT25_INSTR_BIT3 0x08 /* Additional address bit in instr */ 50 51 #define EE_MAXADDRLEN 3 /* 24 bit addresses, up to 2 MBytes */ 52 53 /* Specs often allow 5 msec for a page write, sometimes 20 msec; 54 * it's important to recover from write timeouts. 55 */ 56 #define EE_TIMEOUT 25 57 58 /*-------------------------------------------------------------------------*/ 59 60 #define io_limit PAGE_SIZE /* bytes */ 61 62 static int at25_ee_read(void *priv, unsigned int offset, 63 void *val, size_t count) 64 { 65 struct at25_data *at25 = priv; 66 char *buf = val; 67 u8 command[EE_MAXADDRLEN + 1]; 68 u8 *cp; 69 ssize_t status; 70 struct spi_transfer t[2]; 71 struct spi_message m; 72 u8 instr; 73 74 if (unlikely(offset >= at25->chip.byte_len)) 75 return -EINVAL; 76 if ((offset + count) > at25->chip.byte_len) 77 count = at25->chip.byte_len - offset; 78 if (unlikely(!count)) 79 return -EINVAL; 80 81 cp = command; 82 83 instr = AT25_READ; 84 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 85 if (offset >= (1U << (at25->addrlen * 8))) 86 instr |= AT25_INSTR_BIT3; 87 *cp++ = instr; 88 89 /* 8/16/24-bit address is written MSB first */ 90 switch (at25->addrlen) { 91 default: /* case 3 */ 92 *cp++ = offset >> 16; 93 fallthrough; 94 case 2: 95 *cp++ = offset >> 8; 96 fallthrough; 97 case 1: 98 case 0: /* can't happen: for better codegen */ 99 *cp++ = offset >> 0; 100 } 101 102 spi_message_init(&m); 103 memset(t, 0, sizeof(t)); 104 105 t[0].tx_buf = command; 106 t[0].len = at25->addrlen + 1; 107 spi_message_add_tail(&t[0], &m); 108 109 t[1].rx_buf = buf; 110 t[1].len = count; 111 spi_message_add_tail(&t[1], &m); 112 113 mutex_lock(&at25->lock); 114 115 /* Read it all at once. 116 * 117 * REVISIT that's potentially a problem with large chips, if 118 * other devices on the bus need to be accessed regularly or 119 * this chip is clocked very slowly 120 */ 121 status = spi_sync(at25->spi, &m); 122 dev_dbg(&at25->spi->dev, "read %zu bytes at %d --> %zd\n", 123 count, offset, status); 124 125 mutex_unlock(&at25->lock); 126 return status; 127 } 128 129 static int at25_ee_write(void *priv, unsigned int off, void *val, size_t count) 130 { 131 struct at25_data *at25 = priv; 132 const char *buf = val; 133 int status = 0; 134 unsigned buf_size; 135 u8 *bounce; 136 137 if (unlikely(off >= at25->chip.byte_len)) 138 return -EFBIG; 139 if ((off + count) > at25->chip.byte_len) 140 count = at25->chip.byte_len - off; 141 if (unlikely(!count)) 142 return -EINVAL; 143 144 /* Temp buffer starts with command and address */ 145 buf_size = at25->chip.page_size; 146 if (buf_size > io_limit) 147 buf_size = io_limit; 148 bounce = kmalloc(buf_size + at25->addrlen + 1, GFP_KERNEL); 149 if (!bounce) 150 return -ENOMEM; 151 152 /* For write, rollover is within the page ... so we write at 153 * most one page, then manually roll over to the next page. 154 */ 155 mutex_lock(&at25->lock); 156 do { 157 unsigned long timeout, retries; 158 unsigned segment; 159 unsigned offset = (unsigned) off; 160 u8 *cp = bounce; 161 int sr; 162 u8 instr; 163 164 *cp = AT25_WREN; 165 status = spi_write(at25->spi, cp, 1); 166 if (status < 0) { 167 dev_dbg(&at25->spi->dev, "WREN --> %d\n", status); 168 break; 169 } 170 171 instr = AT25_WRITE; 172 if (at25->chip.flags & EE_INSTR_BIT3_IS_ADDR) 173 if (offset >= (1U << (at25->addrlen * 8))) 174 instr |= AT25_INSTR_BIT3; 175 *cp++ = instr; 176 177 /* 8/16/24-bit address is written MSB first */ 178 switch (at25->addrlen) { 179 default: /* case 3 */ 180 *cp++ = offset >> 16; 181 fallthrough; 182 case 2: 183 *cp++ = offset >> 8; 184 fallthrough; 185 case 1: 186 case 0: /* can't happen: for better codegen */ 187 *cp++ = offset >> 0; 188 } 189 190 /* Write as much of a page as we can */ 191 segment = buf_size - (offset % buf_size); 192 if (segment > count) 193 segment = count; 194 memcpy(cp, buf, segment); 195 status = spi_write(at25->spi, bounce, 196 segment + at25->addrlen + 1); 197 dev_dbg(&at25->spi->dev, "write %u bytes at %u --> %d\n", 198 segment, offset, status); 199 if (status < 0) 200 break; 201 202 /* REVISIT this should detect (or prevent) failed writes 203 * to readonly sections of the EEPROM... 204 */ 205 206 /* Wait for non-busy status */ 207 timeout = jiffies + msecs_to_jiffies(EE_TIMEOUT); 208 retries = 0; 209 do { 210 211 sr = spi_w8r8(at25->spi, AT25_RDSR); 212 if (sr < 0 || (sr & AT25_SR_nRDY)) { 213 dev_dbg(&at25->spi->dev, 214 "rdsr --> %d (%02x)\n", sr, sr); 215 /* at HZ=100, this is sloooow */ 216 msleep(1); 217 continue; 218 } 219 if (!(sr & AT25_SR_nRDY)) 220 break; 221 } while (retries++ < 3 || time_before_eq(jiffies, timeout)); 222 223 if ((sr < 0) || (sr & AT25_SR_nRDY)) { 224 dev_err(&at25->spi->dev, 225 "write %u bytes offset %u, 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; 236 237 } while (count > 0); 238 239 mutex_unlock(&at25->lock); 240 241 kfree(bounce); 242 return status; 243 } 244 245 /*-------------------------------------------------------------------------*/ 246 247 static int at25_fw_to_chip(struct device *dev, struct spi_eeprom *chip) 248 { 249 u32 val; 250 251 memset(chip, 0, sizeof(*chip)); 252 strncpy(chip->name, "at25", sizeof(chip->name)); 253 254 if (device_property_read_u32(dev, "size", &val) == 0 || 255 device_property_read_u32(dev, "at25,byte-len", &val) == 0) { 256 chip->byte_len = val; 257 } else { 258 dev_err(dev, "Error: missing \"size\" property\n"); 259 return -ENODEV; 260 } 261 262 if (device_property_read_u32(dev, "pagesize", &val) == 0 || 263 device_property_read_u32(dev, "at25,page-size", &val) == 0) { 264 chip->page_size = (u16)val; 265 } else { 266 dev_err(dev, "Error: missing \"pagesize\" property\n"); 267 return -ENODEV; 268 } 269 270 if (device_property_read_u32(dev, "at25,addr-mode", &val) == 0) { 271 chip->flags = (u16)val; 272 } else { 273 if (device_property_read_u32(dev, "address-width", &val)) { 274 dev_err(dev, 275 "Error: missing \"address-width\" property\n"); 276 return -ENODEV; 277 } 278 switch (val) { 279 case 9: 280 chip->flags |= EE_INSTR_BIT3_IS_ADDR; 281 fallthrough; 282 case 8: 283 chip->flags |= EE_ADDR1; 284 break; 285 case 16: 286 chip->flags |= EE_ADDR2; 287 break; 288 case 24: 289 chip->flags |= EE_ADDR3; 290 break; 291 default: 292 dev_err(dev, 293 "Error: bad \"address-width\" property: %u\n", 294 val); 295 return -ENODEV; 296 } 297 if (device_property_present(dev, "read-only")) 298 chip->flags |= EE_READONLY; 299 } 300 return 0; 301 } 302 303 static int at25_probe(struct spi_device *spi) 304 { 305 struct at25_data *at25 = NULL; 306 struct spi_eeprom chip; 307 int err; 308 int sr; 309 int addrlen; 310 311 /* Chip description */ 312 if (!spi->dev.platform_data) { 313 err = at25_fw_to_chip(&spi->dev, &chip); 314 if (err) 315 return err; 316 } else 317 chip = *(struct spi_eeprom *)spi->dev.platform_data; 318 319 /* For now we only support 8/16/24 bit addressing */ 320 if (chip.flags & EE_ADDR1) 321 addrlen = 1; 322 else if (chip.flags & EE_ADDR2) 323 addrlen = 2; 324 else if (chip.flags & EE_ADDR3) 325 addrlen = 3; 326 else { 327 dev_dbg(&spi->dev, "unsupported address type\n"); 328 return -EINVAL; 329 } 330 331 /* Ping the chip ... the status register is pretty portable, 332 * unlike probing manufacturer IDs. We do expect that system 333 * firmware didn't write it in the past few milliseconds! 334 */ 335 sr = spi_w8r8(spi, AT25_RDSR); 336 if (sr < 0 || sr & AT25_SR_nRDY) { 337 dev_dbg(&spi->dev, "rdsr --> %d (%02x)\n", sr, sr); 338 return -ENXIO; 339 } 340 341 at25 = devm_kzalloc(&spi->dev, sizeof(struct at25_data), GFP_KERNEL); 342 if (!at25) 343 return -ENOMEM; 344 345 mutex_init(&at25->lock); 346 at25->chip = chip; 347 at25->spi = spi; 348 spi_set_drvdata(spi, at25); 349 at25->addrlen = addrlen; 350 351 at25->nvmem_config.name = dev_name(&spi->dev); 352 at25->nvmem_config.dev = &spi->dev; 353 at25->nvmem_config.read_only = chip.flags & EE_READONLY; 354 at25->nvmem_config.root_only = true; 355 at25->nvmem_config.owner = THIS_MODULE; 356 at25->nvmem_config.compat = true; 357 at25->nvmem_config.base_dev = &spi->dev; 358 at25->nvmem_config.reg_read = at25_ee_read; 359 at25->nvmem_config.reg_write = at25_ee_write; 360 at25->nvmem_config.priv = at25; 361 at25->nvmem_config.stride = 4; 362 at25->nvmem_config.word_size = 1; 363 at25->nvmem_config.size = chip.byte_len; 364 365 at25->nvmem = devm_nvmem_register(&spi->dev, &at25->nvmem_config); 366 if (IS_ERR(at25->nvmem)) 367 return PTR_ERR(at25->nvmem); 368 369 dev_info(&spi->dev, "%d %s %s eeprom%s, pagesize %u\n", 370 (chip.byte_len < 1024) ? chip.byte_len : (chip.byte_len / 1024), 371 (chip.byte_len < 1024) ? "Byte" : "KByte", 372 at25->chip.name, 373 (chip.flags & EE_READONLY) ? " (readonly)" : "", 374 at25->chip.page_size); 375 return 0; 376 } 377 378 /*-------------------------------------------------------------------------*/ 379 380 static const struct of_device_id at25_of_match[] = { 381 { .compatible = "atmel,at25", }, 382 { } 383 }; 384 MODULE_DEVICE_TABLE(of, at25_of_match); 385 386 static struct spi_driver at25_driver = { 387 .driver = { 388 .name = "at25", 389 .of_match_table = at25_of_match, 390 }, 391 .probe = at25_probe, 392 }; 393 394 module_spi_driver(at25_driver); 395 396 MODULE_DESCRIPTION("Driver for most SPI EEPROMs"); 397 MODULE_AUTHOR("David Brownell"); 398 MODULE_LICENSE("GPL"); 399 MODULE_ALIAS("spi:at25"); 400