1===================================== 2MTD NAND Driver Programming Interface 3===================================== 4 5:Author: Thomas Gleixner 6 7Introduction 8============ 9 10The generic NAND driver supports almost all NAND and AG-AND based chips 11and connects them to the Memory Technology Devices (MTD) subsystem of 12the Linux Kernel. 13 14This documentation is provided for developers who want to implement 15board drivers or filesystem drivers suitable for NAND devices. 16 17Known Bugs And Assumptions 18========================== 19 20None. 21 22Documentation hints 23=================== 24 25The function and structure docs are autogenerated. Each function and 26struct member has a short description which is marked with an [XXX] 27identifier. The following chapters explain the meaning of those 28identifiers. 29 30Function identifiers [XXX] 31-------------------------- 32 33The functions are marked with [XXX] identifiers in the short comment. 34The identifiers explain the usage and scope of the functions. Following 35identifiers are used: 36 37- [MTD Interface] 38 39 These functions provide the interface to the MTD kernel API. They are 40 not replaceable and provide functionality which is complete hardware 41 independent. 42 43- [NAND Interface] 44 45 These functions are exported and provide the interface to the NAND 46 kernel API. 47 48- [GENERIC] 49 50 Generic functions are not replaceable and provide functionality which 51 is complete hardware independent. 52 53- [DEFAULT] 54 55 Default functions provide hardware related functionality which is 56 suitable for most of the implementations. These functions can be 57 replaced by the board driver if necessary. Those functions are called 58 via pointers in the NAND chip description structure. The board driver 59 can set the functions which should be replaced by board dependent 60 functions before calling nand_scan(). If the function pointer is 61 NULL on entry to nand_scan() then the pointer is set to the default 62 function which is suitable for the detected chip type. 63 64Struct member identifiers [XXX] 65------------------------------- 66 67The struct members are marked with [XXX] identifiers in the comment. The 68identifiers explain the usage and scope of the members. Following 69identifiers are used: 70 71- [INTERN] 72 73 These members are for NAND driver internal use only and must not be 74 modified. Most of these values are calculated from the chip geometry 75 information which is evaluated during nand_scan(). 76 77- [REPLACEABLE] 78 79 Replaceable members hold hardware related functions which can be 80 provided by the board driver. The board driver can set the functions 81 which should be replaced by board dependent functions before calling 82 nand_scan(). If the function pointer is NULL on entry to 83 nand_scan() then the pointer is set to the default function which is 84 suitable for the detected chip type. 85 86- [BOARDSPECIFIC] 87 88 Board specific members hold hardware related information which must 89 be provided by the board driver. The board driver must set the 90 function pointers and datafields before calling nand_scan(). 91 92- [OPTIONAL] 93 94 Optional members can hold information relevant for the board driver. 95 The generic NAND driver code does not use this information. 96 97Basic board driver 98================== 99 100For most boards it will be sufficient to provide just the basic 101functions and fill out some really board dependent members in the nand 102chip description structure. 103 104Basic defines 105------------- 106 107At least you have to provide a nand_chip structure and a storage for 108the ioremap'ed chip address. You can allocate the nand_chip structure 109using kmalloc or you can allocate it statically. The NAND chip structure 110embeds an mtd structure which will be registered to the MTD subsystem. 111You can extract a pointer to the mtd structure from a nand_chip pointer 112using the nand_to_mtd() helper. 113 114Kmalloc based example 115 116:: 117 118 static struct mtd_info *board_mtd; 119 static void __iomem *baseaddr; 120 121 122Static example 123 124:: 125 126 static struct nand_chip board_chip; 127 static void __iomem *baseaddr; 128 129 130Partition defines 131----------------- 132 133If you want to divide your device into partitions, then define a 134partitioning scheme suitable to your board. 135 136:: 137 138 #define NUM_PARTITIONS 2 139 static struct mtd_partition partition_info[] = { 140 { .name = "Flash partition 1", 141 .offset = 0, 142 .size = 8 * 1024 * 1024 }, 143 { .name = "Flash partition 2", 144 .offset = MTDPART_OFS_NEXT, 145 .size = MTDPART_SIZ_FULL }, 146 }; 147 148 149Hardware control function 150------------------------- 151 152The hardware control function provides access to the control pins of the 153NAND chip(s). The access can be done by GPIO pins or by address lines. 154If you use address lines, make sure that the timing requirements are 155met. 156 157*GPIO based example* 158 159:: 160 161 static void board_hwcontrol(struct mtd_info *mtd, int cmd) 162 { 163 switch(cmd){ 164 case NAND_CTL_SETCLE: /* Set CLE pin high */ break; 165 case NAND_CTL_CLRCLE: /* Set CLE pin low */ break; 166 case NAND_CTL_SETALE: /* Set ALE pin high */ break; 167 case NAND_CTL_CLRALE: /* Set ALE pin low */ break; 168 case NAND_CTL_SETNCE: /* Set nCE pin low */ break; 169 case NAND_CTL_CLRNCE: /* Set nCE pin high */ break; 170 } 171 } 172 173 174*Address lines based example.* It's assumed that the nCE pin is driven 175by a chip select decoder. 176 177:: 178 179 static void board_hwcontrol(struct mtd_info *mtd, int cmd) 180 { 181 struct nand_chip *this = mtd_to_nand(mtd); 182 switch(cmd){ 183 case NAND_CTL_SETCLE: this->IO_ADDR_W |= CLE_ADRR_BIT; break; 184 case NAND_CTL_CLRCLE: this->IO_ADDR_W &= ~CLE_ADRR_BIT; break; 185 case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT; break; 186 case NAND_CTL_CLRALE: this->IO_ADDR_W &= ~ALE_ADRR_BIT; break; 187 } 188 } 189 190 191Device ready function 192--------------------- 193 194If the hardware interface has the ready busy pin of the NAND chip 195connected to a GPIO or other accessible I/O pin, this function is used 196to read back the state of the pin. The function has no arguments and 197should return 0, if the device is busy (R/B pin is low) and 1, if the 198device is ready (R/B pin is high). If the hardware interface does not 199give access to the ready busy pin, then the function must not be defined 200and the function pointer this->dev_ready is set to NULL. 201 202Init function 203------------- 204 205The init function allocates memory and sets up all the board specific 206parameters and function pointers. When everything is set up nand_scan() 207is called. This function tries to detect and identify then chip. If a 208chip is found all the internal data fields are initialized accordingly. 209The structure(s) have to be zeroed out first and then filled with the 210necessary information about the device. 211 212:: 213 214 static int __init board_init (void) 215 { 216 struct nand_chip *this; 217 int err = 0; 218 219 /* Allocate memory for MTD device structure and private data */ 220 this = kzalloc(sizeof(struct nand_chip), GFP_KERNEL); 221 if (!this) { 222 printk ("Unable to allocate NAND MTD device structure.\n"); 223 err = -ENOMEM; 224 goto out; 225 } 226 227 board_mtd = nand_to_mtd(this); 228 229 /* map physical address */ 230 baseaddr = ioremap(CHIP_PHYSICAL_ADDRESS, 1024); 231 if (!baseaddr) { 232 printk("Ioremap to access NAND chip failed\n"); 233 err = -EIO; 234 goto out_mtd; 235 } 236 237 /* Set address of NAND IO lines */ 238 this->IO_ADDR_R = baseaddr; 239 this->IO_ADDR_W = baseaddr; 240 /* Reference hardware control function */ 241 this->hwcontrol = board_hwcontrol; 242 /* Set command delay time, see datasheet for correct value */ 243 this->chip_delay = CHIP_DEPENDEND_COMMAND_DELAY; 244 /* Assign the device ready function, if available */ 245 this->dev_ready = board_dev_ready; 246 this->eccmode = NAND_ECC_SOFT; 247 248 /* Scan to find existence of the device */ 249 if (nand_scan (board_mtd, 1)) { 250 err = -ENXIO; 251 goto out_ior; 252 } 253 254 add_mtd_partitions(board_mtd, partition_info, NUM_PARTITIONS); 255 goto out; 256 257 out_ior: 258 iounmap(baseaddr); 259 out_mtd: 260 kfree (this); 261 out: 262 return err; 263 } 264 module_init(board_init); 265 266 267Exit function 268------------- 269 270The exit function is only necessary if the driver is compiled as a 271module. It releases all resources which are held by the chip driver and 272unregisters the partitions in the MTD layer. 273 274:: 275 276 #ifdef MODULE 277 static void __exit board_cleanup (void) 278 { 279 /* Release resources, unregister device */ 280 nand_release (board_mtd); 281 282 /* unmap physical address */ 283 iounmap(baseaddr); 284 285 /* Free the MTD device structure */ 286 kfree (mtd_to_nand(board_mtd)); 287 } 288 module_exit(board_cleanup); 289 #endif 290 291 292Advanced board driver functions 293=============================== 294 295This chapter describes the advanced functionality of the NAND driver. 296For a list of functions which can be overridden by the board driver see 297the documentation of the nand_chip structure. 298 299Multiple chip control 300--------------------- 301 302The nand driver can control chip arrays. Therefore the board driver must 303provide an own select_chip function. This function must (de)select the 304requested chip. The function pointer in the nand_chip structure must be 305set before calling nand_scan(). The maxchip parameter of nand_scan() 306defines the maximum number of chips to scan for. Make sure that the 307select_chip function can handle the requested number of chips. 308 309The nand driver concatenates the chips to one virtual chip and provides 310this virtual chip to the MTD layer. 311 312*Note: The driver can only handle linear chip arrays of equally sized 313chips. There is no support for parallel arrays which extend the 314buswidth.* 315 316*GPIO based example* 317 318:: 319 320 static void board_select_chip (struct mtd_info *mtd, int chip) 321 { 322 /* Deselect all chips, set all nCE pins high */ 323 GPIO(BOARD_NAND_NCE) |= 0xff; 324 if (chip >= 0) 325 GPIO(BOARD_NAND_NCE) &= ~ (1 << chip); 326 } 327 328 329*Address lines based example.* Its assumed that the nCE pins are 330connected to an address decoder. 331 332:: 333 334 static void board_select_chip (struct mtd_info *mtd, int chip) 335 { 336 struct nand_chip *this = mtd_to_nand(mtd); 337 338 /* Deselect all chips */ 339 this->IO_ADDR_R &= ~BOARD_NAND_ADDR_MASK; 340 this->IO_ADDR_W &= ~BOARD_NAND_ADDR_MASK; 341 switch (chip) { 342 case 0: 343 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIP0; 344 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIP0; 345 break; 346 .... 347 case n: 348 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIPn; 349 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIPn; 350 break; 351 } 352 } 353 354 355Hardware ECC support 356-------------------- 357 358Functions and constants 359~~~~~~~~~~~~~~~~~~~~~~~ 360 361The nand driver supports three different types of hardware ECC. 362 363- NAND_ECC_HW3_256 364 365 Hardware ECC generator providing 3 bytes ECC per 256 byte. 366 367- NAND_ECC_HW3_512 368 369 Hardware ECC generator providing 3 bytes ECC per 512 byte. 370 371- NAND_ECC_HW6_512 372 373 Hardware ECC generator providing 6 bytes ECC per 512 byte. 374 375- NAND_ECC_HW8_512 376 377 Hardware ECC generator providing 6 bytes ECC per 512 byte. 378 379If your hardware generator has a different functionality add it at the 380appropriate place in nand_base.c 381 382The board driver must provide following functions: 383 384- enable_hwecc 385 386 This function is called before reading / writing to the chip. Reset 387 or initialize the hardware generator in this function. The function 388 is called with an argument which let you distinguish between read and 389 write operations. 390 391- calculate_ecc 392 393 This function is called after read / write from / to the chip. 394 Transfer the ECC from the hardware to the buffer. If the option 395 NAND_HWECC_SYNDROME is set then the function is only called on 396 write. See below. 397 398- correct_data 399 400 In case of an ECC error this function is called for error detection 401 and correction. Return 1 respectively 2 in case the error can be 402 corrected. If the error is not correctable return -1. If your 403 hardware generator matches the default algorithm of the nand_ecc 404 software generator then use the correction function provided by 405 nand_ecc instead of implementing duplicated code. 406 407Hardware ECC with syndrome calculation 408~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 409 410Many hardware ECC implementations provide Reed-Solomon codes and 411calculate an error syndrome on read. The syndrome must be converted to a 412standard Reed-Solomon syndrome before calling the error correction code 413in the generic Reed-Solomon library. 414 415The ECC bytes must be placed immediately after the data bytes in order 416to make the syndrome generator work. This is contrary to the usual 417layout used by software ECC. The separation of data and out of band area 418is not longer possible. The nand driver code handles this layout and the 419remaining free bytes in the oob area are managed by the autoplacement 420code. Provide a matching oob-layout in this case. See rts_from4.c and 421diskonchip.c for implementation reference. In those cases we must also 422use bad block tables on FLASH, because the ECC layout is interfering 423with the bad block marker positions. See bad block table support for 424details. 425 426Bad block table support 427----------------------- 428 429Most NAND chips mark the bad blocks at a defined position in the spare 430area. Those blocks must not be erased under any circumstances as the bad 431block information would be lost. It is possible to check the bad block 432mark each time when the blocks are accessed by reading the spare area of 433the first page in the block. This is time consuming so a bad block table 434is used. 435 436The nand driver supports various types of bad block tables. 437 438- Per device 439 440 The bad block table contains all bad block information of the device 441 which can consist of multiple chips. 442 443- Per chip 444 445 A bad block table is used per chip and contains the bad block 446 information for this particular chip. 447 448- Fixed offset 449 450 The bad block table is located at a fixed offset in the chip 451 (device). This applies to various DiskOnChip devices. 452 453- Automatic placed 454 455 The bad block table is automatically placed and detected either at 456 the end or at the beginning of a chip (device) 457 458- Mirrored tables 459 460 The bad block table is mirrored on the chip (device) to allow updates 461 of the bad block table without data loss. 462 463nand_scan() calls the function nand_default_bbt(). 464nand_default_bbt() selects appropriate default bad block table 465descriptors depending on the chip information which was retrieved by 466nand_scan(). 467 468The standard policy is scanning the device for bad blocks and build a 469ram based bad block table which allows faster access than always 470checking the bad block information on the flash chip itself. 471 472Flash based tables 473~~~~~~~~~~~~~~~~~~ 474 475It may be desired or necessary to keep a bad block table in FLASH. For 476AG-AND chips this is mandatory, as they have no factory marked bad 477blocks. They have factory marked good blocks. The marker pattern is 478erased when the block is erased to be reused. So in case of powerloss 479before writing the pattern back to the chip this block would be lost and 480added to the bad blocks. Therefore we scan the chip(s) when we detect 481them the first time for good blocks and store this information in a bad 482block table before erasing any of the blocks. 483 484The blocks in which the tables are stored are protected against 485accidental access by marking them bad in the memory bad block table. The 486bad block table management functions are allowed to circumvent this 487protection. 488 489The simplest way to activate the FLASH based bad block table support is 490to set the option NAND_BBT_USE_FLASH in the bbt_option field of the 491nand chip structure before calling nand_scan(). For AG-AND chips is 492this done by default. This activates the default FLASH based bad block 493table functionality of the NAND driver. The default bad block table 494options are 495 496- Store bad block table per chip 497 498- Use 2 bits per block 499 500- Automatic placement at the end of the chip 501 502- Use mirrored tables with version numbers 503 504- Reserve 4 blocks at the end of the chip 505 506User defined tables 507~~~~~~~~~~~~~~~~~~~ 508 509User defined tables are created by filling out a nand_bbt_descr 510structure and storing the pointer in the nand_chip structure member 511bbt_td before calling nand_scan(). If a mirror table is necessary a 512second structure must be created and a pointer to this structure must be 513stored in bbt_md inside the nand_chip structure. If the bbt_md member 514is set to NULL then only the main table is used and no scan for the 515mirrored table is performed. 516 517The most important field in the nand_bbt_descr structure is the 518options field. The options define most of the table properties. Use the 519predefined constants from rawnand.h to define the options. 520 521- Number of bits per block 522 523 The supported number of bits is 1, 2, 4, 8. 524 525- Table per chip 526 527 Setting the constant NAND_BBT_PERCHIP selects that a bad block 528 table is managed for each chip in a chip array. If this option is not 529 set then a per device bad block table is used. 530 531- Table location is absolute 532 533 Use the option constant NAND_BBT_ABSPAGE and define the absolute 534 page number where the bad block table starts in the field pages. If 535 you have selected bad block tables per chip and you have a multi chip 536 array then the start page must be given for each chip in the chip 537 array. Note: there is no scan for a table ident pattern performed, so 538 the fields pattern, veroffs, offs, len can be left uninitialized 539 540- Table location is automatically detected 541 542 The table can either be located in the first or the last good blocks 543 of the chip (device). Set NAND_BBT_LASTBLOCK to place the bad block 544 table at the end of the chip (device). The bad block tables are 545 marked and identified by a pattern which is stored in the spare area 546 of the first page in the block which holds the bad block table. Store 547 a pointer to the pattern in the pattern field. Further the length of 548 the pattern has to be stored in len and the offset in the spare area 549 must be given in the offs member of the nand_bbt_descr structure. 550 For mirrored bad block tables different patterns are mandatory. 551 552- Table creation 553 554 Set the option NAND_BBT_CREATE to enable the table creation if no 555 table can be found during the scan. Usually this is done only once if 556 a new chip is found. 557 558- Table write support 559 560 Set the option NAND_BBT_WRITE to enable the table write support. 561 This allows the update of the bad block table(s) in case a block has 562 to be marked bad due to wear. The MTD interface function 563 block_markbad is calling the update function of the bad block table. 564 If the write support is enabled then the table is updated on FLASH. 565 566 Note: Write support should only be enabled for mirrored tables with 567 version control. 568 569- Table version control 570 571 Set the option NAND_BBT_VERSION to enable the table version 572 control. It's highly recommended to enable this for mirrored tables 573 with write support. It makes sure that the risk of losing the bad 574 block table information is reduced to the loss of the information 575 about the one worn out block which should be marked bad. The version 576 is stored in 4 consecutive bytes in the spare area of the device. The 577 position of the version number is defined by the member veroffs in 578 the bad block table descriptor. 579 580- Save block contents on write 581 582 In case that the block which holds the bad block table does contain 583 other useful information, set the option NAND_BBT_SAVECONTENT. When 584 the bad block table is written then the whole block is read the bad 585 block table is updated and the block is erased and everything is 586 written back. If this option is not set only the bad block table is 587 written and everything else in the block is ignored and erased. 588 589- Number of reserved blocks 590 591 For automatic placement some blocks must be reserved for bad block 592 table storage. The number of reserved blocks is defined in the 593 maxblocks member of the bad block table description structure. 594 Reserving 4 blocks for mirrored tables should be a reasonable number. 595 This also limits the number of blocks which are scanned for the bad 596 block table ident pattern. 597 598Spare area (auto)placement 599-------------------------- 600 601The nand driver implements different possibilities for placement of 602filesystem data in the spare area, 603 604- Placement defined by fs driver 605 606- Automatic placement 607 608The default placement function is automatic placement. The nand driver 609has built in default placement schemes for the various chiptypes. If due 610to hardware ECC functionality the default placement does not fit then 611the board driver can provide a own placement scheme. 612 613File system drivers can provide a own placement scheme which is used 614instead of the default placement scheme. 615 616Placement schemes are defined by a nand_oobinfo structure 617 618:: 619 620 struct nand_oobinfo { 621 int useecc; 622 int eccbytes; 623 int eccpos[24]; 624 int oobfree[8][2]; 625 }; 626 627 628- useecc 629 630 The useecc member controls the ecc and placement function. The header 631 file include/mtd/mtd-abi.h contains constants to select ecc and 632 placement. MTD_NANDECC_OFF switches off the ecc complete. This is 633 not recommended and available for testing and diagnosis only. 634 MTD_NANDECC_PLACE selects caller defined placement, 635 MTD_NANDECC_AUTOPLACE selects automatic placement. 636 637- eccbytes 638 639 The eccbytes member defines the number of ecc bytes per page. 640 641- eccpos 642 643 The eccpos array holds the byte offsets in the spare area where the 644 ecc codes are placed. 645 646- oobfree 647 648 The oobfree array defines the areas in the spare area which can be 649 used for automatic placement. The information is given in the format 650 {offset, size}. offset defines the start of the usable area, size the 651 length in bytes. More than one area can be defined. The list is 652 terminated by an {0, 0} entry. 653 654Placement defined by fs driver 655~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 656 657The calling function provides a pointer to a nand_oobinfo structure 658which defines the ecc placement. For writes the caller must provide a 659spare area buffer along with the data buffer. The spare area buffer size 660is (number of pages) \* (size of spare area). For reads the buffer size 661is (number of pages) \* ((size of spare area) + (number of ecc steps per 662page) \* sizeof (int)). The driver stores the result of the ecc check 663for each tuple in the spare buffer. The storage sequence is:: 664 665 <spare data page 0><ecc result 0>...<ecc result n> 666 667 ... 668 669 <spare data page n><ecc result 0>...<ecc result n> 670 671This is a legacy mode used by YAFFS1. 672 673If the spare area buffer is NULL then only the ECC placement is done 674according to the given scheme in the nand_oobinfo structure. 675 676Automatic placement 677~~~~~~~~~~~~~~~~~~~ 678 679Automatic placement uses the built in defaults to place the ecc bytes in 680the spare area. If filesystem data have to be stored / read into the 681spare area then the calling function must provide a buffer. The buffer 682size per page is determined by the oobfree array in the nand_oobinfo 683structure. 684 685If the spare area buffer is NULL then only the ECC placement is done 686according to the default builtin scheme. 687 688Spare area autoplacement default schemes 689---------------------------------------- 690 691256 byte pagesize 692~~~~~~~~~~~~~~~~~ 693 694======== ================== =================================================== 695Offset Content Comment 696======== ================== =================================================== 6970x00 ECC byte 0 Error correction code byte 0 6980x01 ECC byte 1 Error correction code byte 1 6990x02 ECC byte 2 Error correction code byte 2 7000x03 Autoplace 0 7010x04 Autoplace 1 7020x05 Bad block marker If any bit in this byte is zero, then this 703 block is bad. This applies only to the first 704 page in a block. In the remaining pages this 705 byte is reserved 7060x06 Autoplace 2 7070x07 Autoplace 3 708======== ================== =================================================== 709 710512 byte pagesize 711~~~~~~~~~~~~~~~~~ 712 713 714============= ================== ============================================== 715Offset Content Comment 716============= ================== ============================================== 7170x00 ECC byte 0 Error correction code byte 0 of the lower 718 256 Byte data in this page 7190x01 ECC byte 1 Error correction code byte 1 of the lower 720 256 Bytes of data in this page 7210x02 ECC byte 2 Error correction code byte 2 of the lower 722 256 Bytes of data in this page 7230x03 ECC byte 3 Error correction code byte 0 of the upper 724 256 Bytes of data in this page 7250x04 reserved reserved 7260x05 Bad block marker If any bit in this byte is zero, then this 727 block is bad. This applies only to the first 728 page in a block. In the remaining pages this 729 byte is reserved 7300x06 ECC byte 4 Error correction code byte 1 of the upper 731 256 Bytes of data in this page 7320x07 ECC byte 5 Error correction code byte 2 of the upper 733 256 Bytes of data in this page 7340x08 - 0x0F Autoplace 0 - 7 735============= ================== ============================================== 736 7372048 byte pagesize 738~~~~~~~~~~~~~~~~~~ 739 740=========== ================== ================================================ 741Offset Content Comment 742=========== ================== ================================================ 7430x00 Bad block marker If any bit in this byte is zero, then this block 744 is bad. This applies only to the first page in a 745 block. In the remaining pages this byte is 746 reserved 7470x01 Reserved Reserved 7480x02-0x27 Autoplace 0 - 37 7490x28 ECC byte 0 Error correction code byte 0 of the first 750 256 Byte data in this page 7510x29 ECC byte 1 Error correction code byte 1 of the first 752 256 Bytes of data in this page 7530x2A ECC byte 2 Error correction code byte 2 of the first 754 256 Bytes data in this page 7550x2B ECC byte 3 Error correction code byte 0 of the second 756 256 Bytes of data in this page 7570x2C ECC byte 4 Error correction code byte 1 of the second 758 256 Bytes of data in this page 7590x2D ECC byte 5 Error correction code byte 2 of the second 760 256 Bytes of data in this page 7610x2E ECC byte 6 Error correction code byte 0 of the third 762 256 Bytes of data in this page 7630x2F ECC byte 7 Error correction code byte 1 of the third 764 256 Bytes of data in this page 7650x30 ECC byte 8 Error correction code byte 2 of the third 766 256 Bytes of data in this page 7670x31 ECC byte 9 Error correction code byte 0 of the fourth 768 256 Bytes of data in this page 7690x32 ECC byte 10 Error correction code byte 1 of the fourth 770 256 Bytes of data in this page 7710x33 ECC byte 11 Error correction code byte 2 of the fourth 772 256 Bytes of data in this page 7730x34 ECC byte 12 Error correction code byte 0 of the fifth 774 256 Bytes of data in this page 7750x35 ECC byte 13 Error correction code byte 1 of the fifth 776 256 Bytes of data in this page 7770x36 ECC byte 14 Error correction code byte 2 of the fifth 778 256 Bytes of data in this page 7790x37 ECC byte 15 Error correction code byte 0 of the sixth 780 256 Bytes of data in this page 7810x38 ECC byte 16 Error correction code byte 1 of the sixth 782 256 Bytes of data in this page 7830x39 ECC byte 17 Error correction code byte 2 of the sixth 784 256 Bytes of data in this page 7850x3A ECC byte 18 Error correction code byte 0 of the seventh 786 256 Bytes of data in this page 7870x3B ECC byte 19 Error correction code byte 1 of the seventh 788 256 Bytes of data in this page 7890x3C ECC byte 20 Error correction code byte 2 of the seventh 790 256 Bytes of data in this page 7910x3D ECC byte 21 Error correction code byte 0 of the eighth 792 256 Bytes of data in this page 7930x3E ECC byte 22 Error correction code byte 1 of the eighth 794 256 Bytes of data in this page 7950x3F ECC byte 23 Error correction code byte 2 of the eighth 796 256 Bytes of data in this page 797=========== ================== ================================================ 798 799Filesystem support 800================== 801 802The NAND driver provides all necessary functions for a filesystem via 803the MTD interface. 804 805Filesystems must be aware of the NAND peculiarities and restrictions. 806One major restrictions of NAND Flash is, that you cannot write as often 807as you want to a page. The consecutive writes to a page, before erasing 808it again, are restricted to 1-3 writes, depending on the manufacturers 809specifications. This applies similar to the spare area. 810 811Therefore NAND aware filesystems must either write in page size chunks 812or hold a writebuffer to collect smaller writes until they sum up to 813pagesize. Available NAND aware filesystems: JFFS2, YAFFS. 814 815The spare area usage to store filesystem data is controlled by the spare 816area placement functionality which is described in one of the earlier 817chapters. 818 819Tools 820===== 821 822The MTD project provides a couple of helpful tools to handle NAND Flash. 823 824- flasherase, flasheraseall: Erase and format FLASH partitions 825 826- nandwrite: write filesystem images to NAND FLASH 827 828- nanddump: dump the contents of a NAND FLASH partitions 829 830These tools are aware of the NAND restrictions. Please use those tools 831instead of complaining about errors which are caused by non NAND aware 832access methods. 833 834Constants 835========= 836 837This chapter describes the constants which might be relevant for a 838driver developer. 839 840Chip option constants 841--------------------- 842 843Constants for chip id table 844~~~~~~~~~~~~~~~~~~~~~~~~~~~ 845 846These constants are defined in rawnand.h. They are OR-ed together to 847describe the chip functionality:: 848 849 /* Buswitdh is 16 bit */ 850 #define NAND_BUSWIDTH_16 0x00000002 851 /* Device supports partial programming without padding */ 852 #define NAND_NO_PADDING 0x00000004 853 /* Chip has cache program function */ 854 #define NAND_CACHEPRG 0x00000008 855 /* Chip has copy back function */ 856 #define NAND_COPYBACK 0x00000010 857 /* AND Chip which has 4 banks and a confusing page / block 858 * assignment. See Renesas datasheet for further information */ 859 #define NAND_IS_AND 0x00000020 860 /* Chip has a array of 4 pages which can be read without 861 * additional ready /busy waits */ 862 #define NAND_4PAGE_ARRAY 0x00000040 863 864 865Constants for runtime options 866~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 867 868These constants are defined in rawnand.h. They are OR-ed together to 869describe the functionality:: 870 871 /* The hw ecc generator provides a syndrome instead a ecc value on read 872 * This can only work if we have the ecc bytes directly behind the 873 * data bytes. Applies for DOC and AG-AND Renesas HW Reed Solomon generators */ 874 #define NAND_HWECC_SYNDROME 0x00020000 875 876 877ECC selection constants 878----------------------- 879 880Use these constants to select the ECC algorithm:: 881 882 /* No ECC. Usage is not recommended ! */ 883 #define NAND_ECC_NONE 0 884 /* Software ECC 3 byte ECC per 256 Byte data */ 885 #define NAND_ECC_SOFT 1 886 /* Hardware ECC 3 byte ECC per 256 Byte data */ 887 #define NAND_ECC_HW3_256 2 888 /* Hardware ECC 3 byte ECC per 512 Byte data */ 889 #define NAND_ECC_HW3_512 3 890 /* Hardware ECC 6 byte ECC per 512 Byte data */ 891 #define NAND_ECC_HW6_512 4 892 /* Hardware ECC 6 byte ECC per 512 Byte data */ 893 #define NAND_ECC_HW8_512 6 894 895 896Hardware control related constants 897---------------------------------- 898 899These constants describe the requested hardware access function when the 900boardspecific hardware control function is called:: 901 902 /* Select the chip by setting nCE to low */ 903 #define NAND_CTL_SETNCE 1 904 /* Deselect the chip by setting nCE to high */ 905 #define NAND_CTL_CLRNCE 2 906 /* Select the command latch by setting CLE to high */ 907 #define NAND_CTL_SETCLE 3 908 /* Deselect the command latch by setting CLE to low */ 909 #define NAND_CTL_CLRCLE 4 910 /* Select the address latch by setting ALE to high */ 911 #define NAND_CTL_SETALE 5 912 /* Deselect the address latch by setting ALE to low */ 913 #define NAND_CTL_CLRALE 6 914 /* Set write protection by setting WP to high. Not used! */ 915 #define NAND_CTL_SETWP 7 916 /* Clear write protection by setting WP to low. Not used! */ 917 #define NAND_CTL_CLRWP 8 918 919 920Bad block table related constants 921--------------------------------- 922 923These constants describe the options used for bad block table 924descriptors:: 925 926 /* Options for the bad block table descriptors */ 927 928 /* The number of bits used per block in the bbt on the device */ 929 #define NAND_BBT_NRBITS_MSK 0x0000000F 930 #define NAND_BBT_1BIT 0x00000001 931 #define NAND_BBT_2BIT 0x00000002 932 #define NAND_BBT_4BIT 0x00000004 933 #define NAND_BBT_8BIT 0x00000008 934 /* The bad block table is in the last good block of the device */ 935 #define NAND_BBT_LASTBLOCK 0x00000010 936 /* The bbt is at the given page, else we must scan for the bbt */ 937 #define NAND_BBT_ABSPAGE 0x00000020 938 /* bbt is stored per chip on multichip devices */ 939 #define NAND_BBT_PERCHIP 0x00000080 940 /* bbt has a version counter at offset veroffs */ 941 #define NAND_BBT_VERSION 0x00000100 942 /* Create a bbt if none axists */ 943 #define NAND_BBT_CREATE 0x00000200 944 /* Write bbt if necessary */ 945 #define NAND_BBT_WRITE 0x00001000 946 /* Read and write back block contents when writing bbt */ 947 #define NAND_BBT_SAVECONTENT 0x00002000 948 949 950Structures 951========== 952 953This chapter contains the autogenerated documentation of the structures 954which are used in the NAND driver and might be relevant for a driver 955developer. Each struct member has a short description which is marked 956with an [XXX] identifier. See the chapter "Documentation hints" for an 957explanation. 958 959.. kernel-doc:: include/linux/mtd/rawnand.h 960 :internal: 961 962Public Functions Provided 963========================= 964 965This chapter contains the autogenerated documentation of the NAND kernel 966API functions which are exported. Each function has a short description 967which is marked with an [XXX] identifier. See the chapter "Documentation 968hints" for an explanation. 969 970.. kernel-doc:: drivers/mtd/nand/nand_base.c 971 :export: 972 973.. kernel-doc:: drivers/mtd/nand/nand_ecc.c 974 :export: 975 976Internal Functions Provided 977=========================== 978 979This chapter contains the autogenerated documentation of the NAND driver 980internal functions. Each function has a short description which is 981marked with an [XXX] identifier. See the chapter "Documentation hints" 982for an explanation. The functions marked with [DEFAULT] might be 983relevant for a board driver developer. 984 985.. kernel-doc:: drivers/mtd/nand/nand_base.c 986 :internal: 987 988.. kernel-doc:: drivers/mtd/nand/nand_bbt.c 989 :internal: 990 991Credits 992======= 993 994The following people have contributed to the NAND driver: 995 9961. Steven J. Hill\ sjhill@realitydiluted.com 997 9982. David Woodhouse\ dwmw2@infradead.org 999 10003. Thomas Gleixner\ tglx@linutronix.de 1001 1002A lot of users have provided bugfixes, improvements and helping hands 1003for testing. Thanks a lot. 1004 1005The following people have contributed to this document: 1006 10071. Thomas Gleixner\ tglx@linutronix.de 1008