1<?xml version="1.0" encoding="UTF-8"?> 2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN" 3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []> 4 5<book id="MTD-NAND-Guide"> 6 <bookinfo> 7 <title>MTD NAND Driver Programming Interface</title> 8 9 <authorgroup> 10 <author> 11 <firstname>Thomas</firstname> 12 <surname>Gleixner</surname> 13 <affiliation> 14 <address> 15 <email>tglx@linutronix.de</email> 16 </address> 17 </affiliation> 18 </author> 19 </authorgroup> 20 21 <copyright> 22 <year>2004</year> 23 <holder>Thomas Gleixner</holder> 24 </copyright> 25 26 <legalnotice> 27 <para> 28 This documentation is free software; you can redistribute 29 it and/or modify it under the terms of the GNU General Public 30 License version 2 as published by the Free Software Foundation. 31 </para> 32 33 <para> 34 This program is distributed in the hope that it will be 35 useful, but WITHOUT ANY WARRANTY; without even the implied 36 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 37 See the GNU General Public License for more details. 38 </para> 39 40 <para> 41 You should have received a copy of the GNU General Public 42 License along with this program; if not, write to the Free 43 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, 44 MA 02111-1307 USA 45 </para> 46 47 <para> 48 For more details see the file COPYING in the source 49 distribution of Linux. 50 </para> 51 </legalnotice> 52 </bookinfo> 53 54<toc></toc> 55 56 <chapter id="intro"> 57 <title>Introduction</title> 58 <para> 59 The generic NAND driver supports almost all NAND and AG-AND based 60 chips and connects them to the Memory Technology Devices (MTD) 61 subsystem of the Linux Kernel. 62 </para> 63 <para> 64 This documentation is provided for developers who want to implement 65 board drivers or filesystem drivers suitable for NAND devices. 66 </para> 67 </chapter> 68 69 <chapter id="bugs"> 70 <title>Known Bugs And Assumptions</title> 71 <para> 72 None. 73 </para> 74 </chapter> 75 76 <chapter id="dochints"> 77 <title>Documentation hints</title> 78 <para> 79 The function and structure docs are autogenerated. Each function and 80 struct member has a short description which is marked with an [XXX] identifier. 81 The following chapters explain the meaning of those identifiers. 82 </para> 83 <sect1 id="Function_identifiers_XXX"> 84 <title>Function identifiers [XXX]</title> 85 <para> 86 The functions are marked with [XXX] identifiers in the short 87 comment. The identifiers explain the usage and scope of the 88 functions. Following identifiers are used: 89 </para> 90 <itemizedlist> 91 <listitem><para> 92 [MTD Interface]</para><para> 93 These functions provide the interface to the MTD kernel API. 94 They are not replaceable and provide functionality 95 which is complete hardware independent. 96 </para></listitem> 97 <listitem><para> 98 [NAND Interface]</para><para> 99 These functions are exported and provide the interface to the NAND kernel API. 100 </para></listitem> 101 <listitem><para> 102 [GENERIC]</para><para> 103 Generic functions are not replaceable and provide functionality 104 which is complete hardware independent. 105 </para></listitem> 106 <listitem><para> 107 [DEFAULT]</para><para> 108 Default functions provide hardware related functionality which is suitable 109 for most of the implementations. These functions can be replaced by the 110 board driver if necessary. Those functions are called via pointers in the 111 NAND chip description structure. The board driver can set the functions which 112 should be replaced by board dependent functions before calling nand_scan(). 113 If the function pointer is NULL on entry to nand_scan() then the pointer 114 is set to the default function which is suitable for the detected chip type. 115 </para></listitem> 116 </itemizedlist> 117 </sect1> 118 <sect1 id="Struct_member_identifiers_XXX"> 119 <title>Struct member identifiers [XXX]</title> 120 <para> 121 The struct members are marked with [XXX] identifiers in the 122 comment. The identifiers explain the usage and scope of the 123 members. Following identifiers are used: 124 </para> 125 <itemizedlist> 126 <listitem><para> 127 [INTERN]</para><para> 128 These members are for NAND driver internal use only and must not be 129 modified. Most of these values are calculated from the chip geometry 130 information which is evaluated during nand_scan(). 131 </para></listitem> 132 <listitem><para> 133 [REPLACEABLE]</para><para> 134 Replaceable members hold hardware related functions which can be 135 provided by the board driver. The board driver can set the functions which 136 should be replaced by board dependent functions before calling nand_scan(). 137 If the function pointer is NULL on entry to nand_scan() then the pointer 138 is set to the default function which is suitable for the detected chip type. 139 </para></listitem> 140 <listitem><para> 141 [BOARDSPECIFIC]</para><para> 142 Board specific members hold hardware related information which must 143 be provided by the board driver. The board driver must set the function 144 pointers and datafields before calling nand_scan(). 145 </para></listitem> 146 <listitem><para> 147 [OPTIONAL]</para><para> 148 Optional members can hold information relevant for the board driver. The 149 generic NAND driver code does not use this information. 150 </para></listitem> 151 </itemizedlist> 152 </sect1> 153 </chapter> 154 155 <chapter id="basicboarddriver"> 156 <title>Basic board driver</title> 157 <para> 158 For most boards it will be sufficient to provide just the 159 basic functions and fill out some really board dependent 160 members in the nand chip description structure. 161 </para> 162 <sect1 id="Basic_defines"> 163 <title>Basic defines</title> 164 <para> 165 At least you have to provide a nand_chip structure 166 and a storage for the ioremap'ed chip address. 167 You can allocate the nand_chip structure using 168 kmalloc or you can allocate it statically. 169 The NAND chip structure embeds an mtd structure 170 which will be registered to the MTD subsystem. 171 You can extract a pointer to the mtd structure 172 from a nand_chip pointer using the nand_to_mtd() 173 helper. 174 </para> 175 <para> 176 Kmalloc based example 177 </para> 178 <programlisting> 179static struct mtd_info *board_mtd; 180static void __iomem *baseaddr; 181 </programlisting> 182 <para> 183 Static example 184 </para> 185 <programlisting> 186static struct nand_chip board_chip; 187static void __iomem *baseaddr; 188 </programlisting> 189 </sect1> 190 <sect1 id="Partition_defines"> 191 <title>Partition defines</title> 192 <para> 193 If you want to divide your device into partitions, then 194 define a partitioning scheme suitable to your board. 195 </para> 196 <programlisting> 197#define NUM_PARTITIONS 2 198static struct mtd_partition partition_info[] = { 199 { .name = "Flash partition 1", 200 .offset = 0, 201 .size = 8 * 1024 * 1024 }, 202 { .name = "Flash partition 2", 203 .offset = MTDPART_OFS_NEXT, 204 .size = MTDPART_SIZ_FULL }, 205}; 206 </programlisting> 207 </sect1> 208 <sect1 id="Hardware_control_functions"> 209 <title>Hardware control function</title> 210 <para> 211 The hardware control function provides access to the 212 control pins of the NAND chip(s). 213 The access can be done by GPIO pins or by address lines. 214 If you use address lines, make sure that the timing 215 requirements are met. 216 </para> 217 <para> 218 <emphasis>GPIO based example</emphasis> 219 </para> 220 <programlisting> 221static void board_hwcontrol(struct mtd_info *mtd, int cmd) 222{ 223 switch(cmd){ 224 case NAND_CTL_SETCLE: /* Set CLE pin high */ break; 225 case NAND_CTL_CLRCLE: /* Set CLE pin low */ break; 226 case NAND_CTL_SETALE: /* Set ALE pin high */ break; 227 case NAND_CTL_CLRALE: /* Set ALE pin low */ break; 228 case NAND_CTL_SETNCE: /* Set nCE pin low */ break; 229 case NAND_CTL_CLRNCE: /* Set nCE pin high */ break; 230 } 231} 232 </programlisting> 233 <para> 234 <emphasis>Address lines based example.</emphasis> It's assumed that the 235 nCE pin is driven by a chip select decoder. 236 </para> 237 <programlisting> 238static void board_hwcontrol(struct mtd_info *mtd, int cmd) 239{ 240 struct nand_chip *this = mtd_to_nand(mtd); 241 switch(cmd){ 242 case NAND_CTL_SETCLE: this->IO_ADDR_W |= CLE_ADRR_BIT; break; 243 case NAND_CTL_CLRCLE: this->IO_ADDR_W &= ~CLE_ADRR_BIT; break; 244 case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT; break; 245 case NAND_CTL_CLRALE: this->IO_ADDR_W &= ~ALE_ADRR_BIT; break; 246 } 247} 248 </programlisting> 249 </sect1> 250 <sect1 id="Device_ready_function"> 251 <title>Device ready function</title> 252 <para> 253 If the hardware interface has the ready busy pin of the NAND chip connected to a 254 GPIO or other accessible I/O pin, this function is used to read back the state of the 255 pin. The function has no arguments and should return 0, if the device is busy (R/B pin 256 is low) and 1, if the device is ready (R/B pin is high). 257 If the hardware interface does not give access to the ready busy pin, then 258 the function must not be defined and the function pointer this->dev_ready is set to NULL. 259 </para> 260 </sect1> 261 <sect1 id="Init_function"> 262 <title>Init function</title> 263 <para> 264 The init function allocates memory and sets up all the board 265 specific parameters and function pointers. When everything 266 is set up nand_scan() is called. This function tries to 267 detect and identify then chip. If a chip is found all the 268 internal data fields are initialized accordingly. 269 The structure(s) have to be zeroed out first and then filled with the necessary 270 information about the device. 271 </para> 272 <programlisting> 273static int __init board_init (void) 274{ 275 struct nand_chip *this; 276 int err = 0; 277 278 /* Allocate memory for MTD device structure and private data */ 279 this = kzalloc(sizeof(struct nand_chip), GFP_KERNEL); 280 if (!this) { 281 printk ("Unable to allocate NAND MTD device structure.\n"); 282 err = -ENOMEM; 283 goto out; 284 } 285 286 board_mtd = nand_to_mtd(this); 287 288 /* map physical address */ 289 baseaddr = ioremap(CHIP_PHYSICAL_ADDRESS, 1024); 290 if (!baseaddr) { 291 printk("Ioremap to access NAND chip failed\n"); 292 err = -EIO; 293 goto out_mtd; 294 } 295 296 /* Set address of NAND IO lines */ 297 this->IO_ADDR_R = baseaddr; 298 this->IO_ADDR_W = baseaddr; 299 /* Reference hardware control function */ 300 this->hwcontrol = board_hwcontrol; 301 /* Set command delay time, see datasheet for correct value */ 302 this->chip_delay = CHIP_DEPENDEND_COMMAND_DELAY; 303 /* Assign the device ready function, if available */ 304 this->dev_ready = board_dev_ready; 305 this->eccmode = NAND_ECC_SOFT; 306 307 /* Scan to find existence of the device */ 308 if (nand_scan (board_mtd, 1)) { 309 err = -ENXIO; 310 goto out_ior; 311 } 312 313 add_mtd_partitions(board_mtd, partition_info, NUM_PARTITIONS); 314 goto out; 315 316out_ior: 317 iounmap(baseaddr); 318out_mtd: 319 kfree (this); 320out: 321 return err; 322} 323module_init(board_init); 324 </programlisting> 325 </sect1> 326 <sect1 id="Exit_function"> 327 <title>Exit function</title> 328 <para> 329 The exit function is only necessary if the driver is 330 compiled as a module. It releases all resources which 331 are held by the chip driver and unregisters the partitions 332 in the MTD layer. 333 </para> 334 <programlisting> 335#ifdef MODULE 336static void __exit board_cleanup (void) 337{ 338 /* Release resources, unregister device */ 339 nand_release (board_mtd); 340 341 /* unmap physical address */ 342 iounmap(baseaddr); 343 344 /* Free the MTD device structure */ 345 kfree (mtd_to_nand(board_mtd)); 346} 347module_exit(board_cleanup); 348#endif 349 </programlisting> 350 </sect1> 351 </chapter> 352 353 <chapter id="boarddriversadvanced"> 354 <title>Advanced board driver functions</title> 355 <para> 356 This chapter describes the advanced functionality of the NAND 357 driver. For a list of functions which can be overridden by the board 358 driver see the documentation of the nand_chip structure. 359 </para> 360 <sect1 id="Multiple_chip_control"> 361 <title>Multiple chip control</title> 362 <para> 363 The nand driver can control chip arrays. Therefore the 364 board driver must provide an own select_chip function. This 365 function must (de)select the requested chip. 366 The function pointer in the nand_chip structure must 367 be set before calling nand_scan(). The maxchip parameter 368 of nand_scan() defines the maximum number of chips to 369 scan for. Make sure that the select_chip function can 370 handle the requested number of chips. 371 </para> 372 <para> 373 The nand driver concatenates the chips to one virtual 374 chip and provides this virtual chip to the MTD layer. 375 </para> 376 <para> 377 <emphasis>Note: The driver can only handle linear chip arrays 378 of equally sized chips. There is no support for 379 parallel arrays which extend the buswidth.</emphasis> 380 </para> 381 <para> 382 <emphasis>GPIO based example</emphasis> 383 </para> 384 <programlisting> 385static void board_select_chip (struct mtd_info *mtd, int chip) 386{ 387 /* Deselect all chips, set all nCE pins high */ 388 GPIO(BOARD_NAND_NCE) |= 0xff; 389 if (chip >= 0) 390 GPIO(BOARD_NAND_NCE) &= ~ (1 << chip); 391} 392 </programlisting> 393 <para> 394 <emphasis>Address lines based example.</emphasis> 395 Its assumed that the nCE pins are connected to an 396 address decoder. 397 </para> 398 <programlisting> 399static void board_select_chip (struct mtd_info *mtd, int chip) 400{ 401 struct nand_chip *this = mtd_to_nand(mtd); 402 403 /* Deselect all chips */ 404 this->IO_ADDR_R &= ~BOARD_NAND_ADDR_MASK; 405 this->IO_ADDR_W &= ~BOARD_NAND_ADDR_MASK; 406 switch (chip) { 407 case 0: 408 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIP0; 409 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIP0; 410 break; 411 .... 412 case n: 413 this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIPn; 414 this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIPn; 415 break; 416 } 417} 418 </programlisting> 419 </sect1> 420 <sect1 id="Hardware_ECC_support"> 421 <title>Hardware ECC support</title> 422 <sect2 id="Functions_and_constants"> 423 <title>Functions and constants</title> 424 <para> 425 The nand driver supports three different types of 426 hardware ECC. 427 <itemizedlist> 428 <listitem><para>NAND_ECC_HW3_256</para><para> 429 Hardware ECC generator providing 3 bytes ECC per 430 256 byte. 431 </para> </listitem> 432 <listitem><para>NAND_ECC_HW3_512</para><para> 433 Hardware ECC generator providing 3 bytes ECC per 434 512 byte. 435 </para> </listitem> 436 <listitem><para>NAND_ECC_HW6_512</para><para> 437 Hardware ECC generator providing 6 bytes ECC per 438 512 byte. 439 </para> </listitem> 440 <listitem><para>NAND_ECC_HW8_512</para><para> 441 Hardware ECC generator providing 6 bytes ECC per 442 512 byte. 443 </para> </listitem> 444 </itemizedlist> 445 If your hardware generator has a different functionality 446 add it at the appropriate place in nand_base.c 447 </para> 448 <para> 449 The board driver must provide following functions: 450 <itemizedlist> 451 <listitem><para>enable_hwecc</para><para> 452 This function is called before reading / writing to 453 the chip. Reset or initialize the hardware generator 454 in this function. The function is called with an 455 argument which let you distinguish between read 456 and write operations. 457 </para> </listitem> 458 <listitem><para>calculate_ecc</para><para> 459 This function is called after read / write from / to 460 the chip. Transfer the ECC from the hardware to 461 the buffer. If the option NAND_HWECC_SYNDROME is set 462 then the function is only called on write. See below. 463 </para> </listitem> 464 <listitem><para>correct_data</para><para> 465 In case of an ECC error this function is called for 466 error detection and correction. Return 1 respectively 2 467 in case the error can be corrected. If the error is 468 not correctable return -1. If your hardware generator 469 matches the default algorithm of the nand_ecc software 470 generator then use the correction function provided 471 by nand_ecc instead of implementing duplicated code. 472 </para> </listitem> 473 </itemizedlist> 474 </para> 475 </sect2> 476 <sect2 id="Hardware_ECC_with_syndrome_calculation"> 477 <title>Hardware ECC with syndrome calculation</title> 478 <para> 479 Many hardware ECC implementations provide Reed-Solomon 480 codes and calculate an error syndrome on read. The syndrome 481 must be converted to a standard Reed-Solomon syndrome 482 before calling the error correction code in the generic 483 Reed-Solomon library. 484 </para> 485 <para> 486 The ECC bytes must be placed immediately after the data 487 bytes in order to make the syndrome generator work. This 488 is contrary to the usual layout used by software ECC. The 489 separation of data and out of band area is not longer 490 possible. The nand driver code handles this layout and 491 the remaining free bytes in the oob area are managed by 492 the autoplacement code. Provide a matching oob-layout 493 in this case. See rts_from4.c and diskonchip.c for 494 implementation reference. In those cases we must also 495 use bad block tables on FLASH, because the ECC layout is 496 interfering with the bad block marker positions. 497 See bad block table support for details. 498 </para> 499 </sect2> 500 </sect1> 501 <sect1 id="Bad_Block_table_support"> 502 <title>Bad block table support</title> 503 <para> 504 Most NAND chips mark the bad blocks at a defined 505 position in the spare area. Those blocks must 506 not be erased under any circumstances as the bad 507 block information would be lost. 508 It is possible to check the bad block mark each 509 time when the blocks are accessed by reading the 510 spare area of the first page in the block. This 511 is time consuming so a bad block table is used. 512 </para> 513 <para> 514 The nand driver supports various types of bad block 515 tables. 516 <itemizedlist> 517 <listitem><para>Per device</para><para> 518 The bad block table contains all bad block information 519 of the device which can consist of multiple chips. 520 </para> </listitem> 521 <listitem><para>Per chip</para><para> 522 A bad block table is used per chip and contains the 523 bad block information for this particular chip. 524 </para> </listitem> 525 <listitem><para>Fixed offset</para><para> 526 The bad block table is located at a fixed offset 527 in the chip (device). This applies to various 528 DiskOnChip devices. 529 </para> </listitem> 530 <listitem><para>Automatic placed</para><para> 531 The bad block table is automatically placed and 532 detected either at the end or at the beginning 533 of a chip (device) 534 </para> </listitem> 535 <listitem><para>Mirrored tables</para><para> 536 The bad block table is mirrored on the chip (device) to 537 allow updates of the bad block table without data loss. 538 </para> </listitem> 539 </itemizedlist> 540 </para> 541 <para> 542 nand_scan() calls the function nand_default_bbt(). 543 nand_default_bbt() selects appropriate default 544 bad block table descriptors depending on the chip information 545 which was retrieved by nand_scan(). 546 </para> 547 <para> 548 The standard policy is scanning the device for bad 549 blocks and build a ram based bad block table which 550 allows faster access than always checking the 551 bad block information on the flash chip itself. 552 </para> 553 <sect2 id="Flash_based_tables"> 554 <title>Flash based tables</title> 555 <para> 556 It may be desired or necessary to keep a bad block table in FLASH. 557 For AG-AND chips this is mandatory, as they have no factory marked 558 bad blocks. They have factory marked good blocks. The marker pattern 559 is erased when the block is erased to be reused. So in case of 560 powerloss before writing the pattern back to the chip this block 561 would be lost and added to the bad blocks. Therefore we scan the 562 chip(s) when we detect them the first time for good blocks and 563 store this information in a bad block table before erasing any 564 of the blocks. 565 </para> 566 <para> 567 The blocks in which the tables are stored are protected against 568 accidental access by marking them bad in the memory bad block 569 table. The bad block table management functions are allowed 570 to circumvent this protection. 571 </para> 572 <para> 573 The simplest way to activate the FLASH based bad block table support 574 is to set the option NAND_BBT_USE_FLASH in the bbt_option field of 575 the nand chip structure before calling nand_scan(). For AG-AND 576 chips is this done by default. 577 This activates the default FLASH based bad block table functionality 578 of the NAND driver. The default bad block table options are 579 <itemizedlist> 580 <listitem><para>Store bad block table per chip</para></listitem> 581 <listitem><para>Use 2 bits per block</para></listitem> 582 <listitem><para>Automatic placement at the end of the chip</para></listitem> 583 <listitem><para>Use mirrored tables with version numbers</para></listitem> 584 <listitem><para>Reserve 4 blocks at the end of the chip</para></listitem> 585 </itemizedlist> 586 </para> 587 </sect2> 588 <sect2 id="User_defined_tables"> 589 <title>User defined tables</title> 590 <para> 591 User defined tables are created by filling out a 592 nand_bbt_descr structure and storing the pointer in the 593 nand_chip structure member bbt_td before calling nand_scan(). 594 If a mirror table is necessary a second structure must be 595 created and a pointer to this structure must be stored 596 in bbt_md inside the nand_chip structure. If the bbt_md 597 member is set to NULL then only the main table is used 598 and no scan for the mirrored table is performed. 599 </para> 600 <para> 601 The most important field in the nand_bbt_descr structure 602 is the options field. The options define most of the 603 table properties. Use the predefined constants from 604 nand.h to define the options. 605 <itemizedlist> 606 <listitem><para>Number of bits per block</para> 607 <para>The supported number of bits is 1, 2, 4, 8.</para></listitem> 608 <listitem><para>Table per chip</para> 609 <para>Setting the constant NAND_BBT_PERCHIP selects that 610 a bad block table is managed for each chip in a chip array. 611 If this option is not set then a per device bad block table 612 is used.</para></listitem> 613 <listitem><para>Table location is absolute</para> 614 <para>Use the option constant NAND_BBT_ABSPAGE and 615 define the absolute page number where the bad block 616 table starts in the field pages. If you have selected bad block 617 tables per chip and you have a multi chip array then the start page 618 must be given for each chip in the chip array. Note: there is no scan 619 for a table ident pattern performed, so the fields 620 pattern, veroffs, offs, len can be left uninitialized</para></listitem> 621 <listitem><para>Table location is automatically detected</para> 622 <para>The table can either be located in the first or the last good 623 blocks of the chip (device). Set NAND_BBT_LASTBLOCK to place 624 the bad block table at the end of the chip (device). The 625 bad block tables are marked and identified by a pattern which 626 is stored in the spare area of the first page in the block which 627 holds the bad block table. Store a pointer to the pattern 628 in the pattern field. Further the length of the pattern has to be 629 stored in len and the offset in the spare area must be given 630 in the offs member of the nand_bbt_descr structure. For mirrored 631 bad block tables different patterns are mandatory.</para></listitem> 632 <listitem><para>Table creation</para> 633 <para>Set the option NAND_BBT_CREATE to enable the table creation 634 if no table can be found during the scan. Usually this is done only 635 once if a new chip is found. </para></listitem> 636 <listitem><para>Table write support</para> 637 <para>Set the option NAND_BBT_WRITE to enable the table write support. 638 This allows the update of the bad block table(s) in case a block has 639 to be marked bad due to wear. The MTD interface function block_markbad 640 is calling the update function of the bad block table. If the write 641 support is enabled then the table is updated on FLASH.</para> 642 <para> 643 Note: Write support should only be enabled for mirrored tables with 644 version control. 645 </para></listitem> 646 <listitem><para>Table version control</para> 647 <para>Set the option NAND_BBT_VERSION to enable the table version control. 648 It's highly recommended to enable this for mirrored tables with write 649 support. It makes sure that the risk of losing the bad block 650 table information is reduced to the loss of the information about the 651 one worn out block which should be marked bad. The version is stored in 652 4 consecutive bytes in the spare area of the device. The position of 653 the version number is defined by the member veroffs in the bad block table 654 descriptor.</para></listitem> 655 <listitem><para>Save block contents on write</para> 656 <para> 657 In case that the block which holds the bad block table does contain 658 other useful information, set the option NAND_BBT_SAVECONTENT. When 659 the bad block table is written then the whole block is read the bad 660 block table is updated and the block is erased and everything is 661 written back. If this option is not set only the bad block table 662 is written and everything else in the block is ignored and erased. 663 </para></listitem> 664 <listitem><para>Number of reserved blocks</para> 665 <para> 666 For automatic placement some blocks must be reserved for 667 bad block table storage. The number of reserved blocks is defined 668 in the maxblocks member of the bad block table description structure. 669 Reserving 4 blocks for mirrored tables should be a reasonable number. 670 This also limits the number of blocks which are scanned for the bad 671 block table ident pattern. 672 </para></listitem> 673 </itemizedlist> 674 </para> 675 </sect2> 676 </sect1> 677 <sect1 id="Spare_area_placement"> 678 <title>Spare area (auto)placement</title> 679 <para> 680 The nand driver implements different possibilities for 681 placement of filesystem data in the spare area, 682 <itemizedlist> 683 <listitem><para>Placement defined by fs driver</para></listitem> 684 <listitem><para>Automatic placement</para></listitem> 685 </itemizedlist> 686 The default placement function is automatic placement. The 687 nand driver has built in default placement schemes for the 688 various chiptypes. If due to hardware ECC functionality the 689 default placement does not fit then the board driver can 690 provide a own placement scheme. 691 </para> 692 <para> 693 File system drivers can provide a own placement scheme which 694 is used instead of the default placement scheme. 695 </para> 696 <para> 697 Placement schemes are defined by a nand_oobinfo structure 698 <programlisting> 699struct nand_oobinfo { 700 int useecc; 701 int eccbytes; 702 int eccpos[24]; 703 int oobfree[8][2]; 704}; 705 </programlisting> 706 <itemizedlist> 707 <listitem><para>useecc</para><para> 708 The useecc member controls the ecc and placement function. The header 709 file include/mtd/mtd-abi.h contains constants to select ecc and 710 placement. MTD_NANDECC_OFF switches off the ecc complete. This is 711 not recommended and available for testing and diagnosis only. 712 MTD_NANDECC_PLACE selects caller defined placement, MTD_NANDECC_AUTOPLACE 713 selects automatic placement. 714 </para></listitem> 715 <listitem><para>eccbytes</para><para> 716 The eccbytes member defines the number of ecc bytes per page. 717 </para></listitem> 718 <listitem><para>eccpos</para><para> 719 The eccpos array holds the byte offsets in the spare area where 720 the ecc codes are placed. 721 </para></listitem> 722 <listitem><para>oobfree</para><para> 723 The oobfree array defines the areas in the spare area which can be 724 used for automatic placement. The information is given in the format 725 {offset, size}. offset defines the start of the usable area, size the 726 length in bytes. More than one area can be defined. The list is terminated 727 by an {0, 0} entry. 728 </para></listitem> 729 </itemizedlist> 730 </para> 731 <sect2 id="Placement_defined_by_fs_driver"> 732 <title>Placement defined by fs driver</title> 733 <para> 734 The calling function provides a pointer to a nand_oobinfo 735 structure which defines the ecc placement. For writes the 736 caller must provide a spare area buffer along with the 737 data buffer. The spare area buffer size is (number of pages) * 738 (size of spare area). For reads the buffer size is 739 (number of pages) * ((size of spare area) + (number of ecc 740 steps per page) * sizeof (int)). The driver stores the 741 result of the ecc check for each tuple in the spare buffer. 742 The storage sequence is 743 </para> 744 <para> 745 <spare data page 0><ecc result 0>...<ecc result n> 746 </para> 747 <para> 748 ... 749 </para> 750 <para> 751 <spare data page n><ecc result 0>...<ecc result n> 752 </para> 753 <para> 754 This is a legacy mode used by YAFFS1. 755 </para> 756 <para> 757 If the spare area buffer is NULL then only the ECC placement is 758 done according to the given scheme in the nand_oobinfo structure. 759 </para> 760 </sect2> 761 <sect2 id="Automatic_placement"> 762 <title>Automatic placement</title> 763 <para> 764 Automatic placement uses the built in defaults to place the 765 ecc bytes in the spare area. If filesystem data have to be stored / 766 read into the spare area then the calling function must provide a 767 buffer. The buffer size per page is determined by the oobfree array in 768 the nand_oobinfo structure. 769 </para> 770 <para> 771 If the spare area buffer is NULL then only the ECC placement is 772 done according to the default builtin scheme. 773 </para> 774 </sect2> 775 </sect1> 776 <sect1 id="Spare_area_autoplacement_default"> 777 <title>Spare area autoplacement default schemes</title> 778 <sect2 id="pagesize_256"> 779 <title>256 byte pagesize</title> 780<informaltable><tgroup cols="3"><tbody> 781<row> 782<entry>Offset</entry> 783<entry>Content</entry> 784<entry>Comment</entry> 785</row> 786<row> 787<entry>0x00</entry> 788<entry>ECC byte 0</entry> 789<entry>Error correction code byte 0</entry> 790</row> 791<row> 792<entry>0x01</entry> 793<entry>ECC byte 1</entry> 794<entry>Error correction code byte 1</entry> 795</row> 796<row> 797<entry>0x02</entry> 798<entry>ECC byte 2</entry> 799<entry>Error correction code byte 2</entry> 800</row> 801<row> 802<entry>0x03</entry> 803<entry>Autoplace 0</entry> 804<entry></entry> 805</row> 806<row> 807<entry>0x04</entry> 808<entry>Autoplace 1</entry> 809<entry></entry> 810</row> 811<row> 812<entry>0x05</entry> 813<entry>Bad block marker</entry> 814<entry>If any bit in this byte is zero, then this block is bad. 815This applies only to the first page in a block. In the remaining 816pages this byte is reserved</entry> 817</row> 818<row> 819<entry>0x06</entry> 820<entry>Autoplace 2</entry> 821<entry></entry> 822</row> 823<row> 824<entry>0x07</entry> 825<entry>Autoplace 3</entry> 826<entry></entry> 827</row> 828</tbody></tgroup></informaltable> 829 </sect2> 830 <sect2 id="pagesize_512"> 831 <title>512 byte pagesize</title> 832<informaltable><tgroup cols="3"><tbody> 833<row> 834<entry>Offset</entry> 835<entry>Content</entry> 836<entry>Comment</entry> 837</row> 838<row> 839<entry>0x00</entry> 840<entry>ECC byte 0</entry> 841<entry>Error correction code byte 0 of the lower 256 Byte data in 842this page</entry> 843</row> 844<row> 845<entry>0x01</entry> 846<entry>ECC byte 1</entry> 847<entry>Error correction code byte 1 of the lower 256 Bytes of data 848in this page</entry> 849</row> 850<row> 851<entry>0x02</entry> 852<entry>ECC byte 2</entry> 853<entry>Error correction code byte 2 of the lower 256 Bytes of data 854in this page</entry> 855</row> 856<row> 857<entry>0x03</entry> 858<entry>ECC byte 3</entry> 859<entry>Error correction code byte 0 of the upper 256 Bytes of data 860in this page</entry> 861</row> 862<row> 863<entry>0x04</entry> 864<entry>reserved</entry> 865<entry>reserved</entry> 866</row> 867<row> 868<entry>0x05</entry> 869<entry>Bad block marker</entry> 870<entry>If any bit in this byte is zero, then this block is bad. 871This applies only to the first page in a block. In the remaining 872pages this byte is reserved</entry> 873</row> 874<row> 875<entry>0x06</entry> 876<entry>ECC byte 4</entry> 877<entry>Error correction code byte 1 of the upper 256 Bytes of data 878in this page</entry> 879</row> 880<row> 881<entry>0x07</entry> 882<entry>ECC byte 5</entry> 883<entry>Error correction code byte 2 of the upper 256 Bytes of data 884in this page</entry> 885</row> 886<row> 887<entry>0x08 - 0x0F</entry> 888<entry>Autoplace 0 - 7</entry> 889<entry></entry> 890</row> 891</tbody></tgroup></informaltable> 892 </sect2> 893 <sect2 id="pagesize_2048"> 894 <title>2048 byte pagesize</title> 895<informaltable><tgroup cols="3"><tbody> 896<row> 897<entry>Offset</entry> 898<entry>Content</entry> 899<entry>Comment</entry> 900</row> 901<row> 902<entry>0x00</entry> 903<entry>Bad block marker</entry> 904<entry>If any bit in this byte is zero, then this block is bad. 905This applies only to the first page in a block. In the remaining 906pages this byte is reserved</entry> 907</row> 908<row> 909<entry>0x01</entry> 910<entry>Reserved</entry> 911<entry>Reserved</entry> 912</row> 913<row> 914<entry>0x02-0x27</entry> 915<entry>Autoplace 0 - 37</entry> 916<entry></entry> 917</row> 918<row> 919<entry>0x28</entry> 920<entry>ECC byte 0</entry> 921<entry>Error correction code byte 0 of the first 256 Byte data in 922this page</entry> 923</row> 924<row> 925<entry>0x29</entry> 926<entry>ECC byte 1</entry> 927<entry>Error correction code byte 1 of the first 256 Bytes of data 928in this page</entry> 929</row> 930<row> 931<entry>0x2A</entry> 932<entry>ECC byte 2</entry> 933<entry>Error correction code byte 2 of the first 256 Bytes data in 934this page</entry> 935</row> 936<row> 937<entry>0x2B</entry> 938<entry>ECC byte 3</entry> 939<entry>Error correction code byte 0 of the second 256 Bytes of data 940in this page</entry> 941</row> 942<row> 943<entry>0x2C</entry> 944<entry>ECC byte 4</entry> 945<entry>Error correction code byte 1 of the second 256 Bytes of data 946in this page</entry> 947</row> 948<row> 949<entry>0x2D</entry> 950<entry>ECC byte 5</entry> 951<entry>Error correction code byte 2 of the second 256 Bytes of data 952in this page</entry> 953</row> 954<row> 955<entry>0x2E</entry> 956<entry>ECC byte 6</entry> 957<entry>Error correction code byte 0 of the third 256 Bytes of data 958in this page</entry> 959</row> 960<row> 961<entry>0x2F</entry> 962<entry>ECC byte 7</entry> 963<entry>Error correction code byte 1 of the third 256 Bytes of data 964in this page</entry> 965</row> 966<row> 967<entry>0x30</entry> 968<entry>ECC byte 8</entry> 969<entry>Error correction code byte 2 of the third 256 Bytes of data 970in this page</entry> 971</row> 972<row> 973<entry>0x31</entry> 974<entry>ECC byte 9</entry> 975<entry>Error correction code byte 0 of the fourth 256 Bytes of data 976in this page</entry> 977</row> 978<row> 979<entry>0x32</entry> 980<entry>ECC byte 10</entry> 981<entry>Error correction code byte 1 of the fourth 256 Bytes of data 982in this page</entry> 983</row> 984<row> 985<entry>0x33</entry> 986<entry>ECC byte 11</entry> 987<entry>Error correction code byte 2 of the fourth 256 Bytes of data 988in this page</entry> 989</row> 990<row> 991<entry>0x34</entry> 992<entry>ECC byte 12</entry> 993<entry>Error correction code byte 0 of the fifth 256 Bytes of data 994in this page</entry> 995</row> 996<row> 997<entry>0x35</entry> 998<entry>ECC byte 13</entry> 999<entry>Error correction code byte 1 of the fifth 256 Bytes of data 1000in this page</entry> 1001</row> 1002<row> 1003<entry>0x36</entry> 1004<entry>ECC byte 14</entry> 1005<entry>Error correction code byte 2 of the fifth 256 Bytes of data 1006in this page</entry> 1007</row> 1008<row> 1009<entry>0x37</entry> 1010<entry>ECC byte 15</entry> 1011<entry>Error correction code byte 0 of the sixt 256 Bytes of data 1012in this page</entry> 1013</row> 1014<row> 1015<entry>0x38</entry> 1016<entry>ECC byte 16</entry> 1017<entry>Error correction code byte 1 of the sixt 256 Bytes of data 1018in this page</entry> 1019</row> 1020<row> 1021<entry>0x39</entry> 1022<entry>ECC byte 17</entry> 1023<entry>Error correction code byte 2 of the sixt 256 Bytes of data 1024in this page</entry> 1025</row> 1026<row> 1027<entry>0x3A</entry> 1028<entry>ECC byte 18</entry> 1029<entry>Error correction code byte 0 of the seventh 256 Bytes of 1030data in this page</entry> 1031</row> 1032<row> 1033<entry>0x3B</entry> 1034<entry>ECC byte 19</entry> 1035<entry>Error correction code byte 1 of the seventh 256 Bytes of 1036data in this page</entry> 1037</row> 1038<row> 1039<entry>0x3C</entry> 1040<entry>ECC byte 20</entry> 1041<entry>Error correction code byte 2 of the seventh 256 Bytes of 1042data in this page</entry> 1043</row> 1044<row> 1045<entry>0x3D</entry> 1046<entry>ECC byte 21</entry> 1047<entry>Error correction code byte 0 of the eighth 256 Bytes of data 1048in this page</entry> 1049</row> 1050<row> 1051<entry>0x3E</entry> 1052<entry>ECC byte 22</entry> 1053<entry>Error correction code byte 1 of the eighth 256 Bytes of data 1054in this page</entry> 1055</row> 1056<row> 1057<entry>0x3F</entry> 1058<entry>ECC byte 23</entry> 1059<entry>Error correction code byte 2 of the eighth 256 Bytes of data 1060in this page</entry> 1061</row> 1062</tbody></tgroup></informaltable> 1063 </sect2> 1064 </sect1> 1065 </chapter> 1066 1067 <chapter id="filesystems"> 1068 <title>Filesystem support</title> 1069 <para> 1070 The NAND driver provides all necessary functions for a 1071 filesystem via the MTD interface. 1072 </para> 1073 <para> 1074 Filesystems must be aware of the NAND peculiarities and 1075 restrictions. One major restrictions of NAND Flash is, that you cannot 1076 write as often as you want to a page. The consecutive writes to a page, 1077 before erasing it again, are restricted to 1-3 writes, depending on the 1078 manufacturers specifications. This applies similar to the spare area. 1079 </para> 1080 <para> 1081 Therefore NAND aware filesystems must either write in page size chunks 1082 or hold a writebuffer to collect smaller writes until they sum up to 1083 pagesize. Available NAND aware filesystems: JFFS2, YAFFS. 1084 </para> 1085 <para> 1086 The spare area usage to store filesystem data is controlled by 1087 the spare area placement functionality which is described in one 1088 of the earlier chapters. 1089 </para> 1090 </chapter> 1091 <chapter id="tools"> 1092 <title>Tools</title> 1093 <para> 1094 The MTD project provides a couple of helpful tools to handle NAND Flash. 1095 <itemizedlist> 1096 <listitem><para>flasherase, flasheraseall: Erase and format FLASH partitions</para></listitem> 1097 <listitem><para>nandwrite: write filesystem images to NAND FLASH</para></listitem> 1098 <listitem><para>nanddump: dump the contents of a NAND FLASH partitions</para></listitem> 1099 </itemizedlist> 1100 </para> 1101 <para> 1102 These tools are aware of the NAND restrictions. Please use those tools 1103 instead of complaining about errors which are caused by non NAND aware 1104 access methods. 1105 </para> 1106 </chapter> 1107 1108 <chapter id="defines"> 1109 <title>Constants</title> 1110 <para> 1111 This chapter describes the constants which might be relevant for a driver developer. 1112 </para> 1113 <sect1 id="Chip_option_constants"> 1114 <title>Chip option constants</title> 1115 <sect2 id="Constants_for_chip_id_table"> 1116 <title>Constants for chip id table</title> 1117 <para> 1118 These constants are defined in nand.h. They are ored together to describe 1119 the chip functionality. 1120 <programlisting> 1121/* Buswitdh is 16 bit */ 1122#define NAND_BUSWIDTH_16 0x00000002 1123/* Device supports partial programming without padding */ 1124#define NAND_NO_PADDING 0x00000004 1125/* Chip has cache program function */ 1126#define NAND_CACHEPRG 0x00000008 1127/* Chip has copy back function */ 1128#define NAND_COPYBACK 0x00000010 1129/* AND Chip which has 4 banks and a confusing page / block 1130 * assignment. See Renesas datasheet for further information */ 1131#define NAND_IS_AND 0x00000020 1132/* Chip has a array of 4 pages which can be read without 1133 * additional ready /busy waits */ 1134#define NAND_4PAGE_ARRAY 0x00000040 1135 </programlisting> 1136 </para> 1137 </sect2> 1138 <sect2 id="Constants_for_runtime_options"> 1139 <title>Constants for runtime options</title> 1140 <para> 1141 These constants are defined in nand.h. They are ored together to describe 1142 the functionality. 1143 <programlisting> 1144/* The hw ecc generator provides a syndrome instead a ecc value on read 1145 * This can only work if we have the ecc bytes directly behind the 1146 * data bytes. Applies for DOC and AG-AND Renesas HW Reed Solomon generators */ 1147#define NAND_HWECC_SYNDROME 0x00020000 1148 </programlisting> 1149 </para> 1150 </sect2> 1151 </sect1> 1152 1153 <sect1 id="EEC_selection_constants"> 1154 <title>ECC selection constants</title> 1155 <para> 1156 Use these constants to select the ECC algorithm. 1157 <programlisting> 1158/* No ECC. Usage is not recommended ! */ 1159#define NAND_ECC_NONE 0 1160/* Software ECC 3 byte ECC per 256 Byte data */ 1161#define NAND_ECC_SOFT 1 1162/* Hardware ECC 3 byte ECC per 256 Byte data */ 1163#define NAND_ECC_HW3_256 2 1164/* Hardware ECC 3 byte ECC per 512 Byte data */ 1165#define NAND_ECC_HW3_512 3 1166/* Hardware ECC 6 byte ECC per 512 Byte data */ 1167#define NAND_ECC_HW6_512 4 1168/* Hardware ECC 6 byte ECC per 512 Byte data */ 1169#define NAND_ECC_HW8_512 6 1170 </programlisting> 1171 </para> 1172 </sect1> 1173 1174 <sect1 id="Hardware_control_related_constants"> 1175 <title>Hardware control related constants</title> 1176 <para> 1177 These constants describe the requested hardware access function when 1178 the boardspecific hardware control function is called 1179 <programlisting> 1180/* Select the chip by setting nCE to low */ 1181#define NAND_CTL_SETNCE 1 1182/* Deselect the chip by setting nCE to high */ 1183#define NAND_CTL_CLRNCE 2 1184/* Select the command latch by setting CLE to high */ 1185#define NAND_CTL_SETCLE 3 1186/* Deselect the command latch by setting CLE to low */ 1187#define NAND_CTL_CLRCLE 4 1188/* Select the address latch by setting ALE to high */ 1189#define NAND_CTL_SETALE 5 1190/* Deselect the address latch by setting ALE to low */ 1191#define NAND_CTL_CLRALE 6 1192/* Set write protection by setting WP to high. Not used! */ 1193#define NAND_CTL_SETWP 7 1194/* Clear write protection by setting WP to low. Not used! */ 1195#define NAND_CTL_CLRWP 8 1196 </programlisting> 1197 </para> 1198 </sect1> 1199 1200 <sect1 id="Bad_block_table_constants"> 1201 <title>Bad block table related constants</title> 1202 <para> 1203 These constants describe the options used for bad block 1204 table descriptors. 1205 <programlisting> 1206/* Options for the bad block table descriptors */ 1207 1208/* The number of bits used per block in the bbt on the device */ 1209#define NAND_BBT_NRBITS_MSK 0x0000000F 1210#define NAND_BBT_1BIT 0x00000001 1211#define NAND_BBT_2BIT 0x00000002 1212#define NAND_BBT_4BIT 0x00000004 1213#define NAND_BBT_8BIT 0x00000008 1214/* The bad block table is in the last good block of the device */ 1215#define NAND_BBT_LASTBLOCK 0x00000010 1216/* The bbt is at the given page, else we must scan for the bbt */ 1217#define NAND_BBT_ABSPAGE 0x00000020 1218/* bbt is stored per chip on multichip devices */ 1219#define NAND_BBT_PERCHIP 0x00000080 1220/* bbt has a version counter at offset veroffs */ 1221#define NAND_BBT_VERSION 0x00000100 1222/* Create a bbt if none axists */ 1223#define NAND_BBT_CREATE 0x00000200 1224/* Write bbt if necessary */ 1225#define NAND_BBT_WRITE 0x00001000 1226/* Read and write back block contents when writing bbt */ 1227#define NAND_BBT_SAVECONTENT 0x00002000 1228 </programlisting> 1229 </para> 1230 </sect1> 1231 1232 </chapter> 1233 1234 <chapter id="structs"> 1235 <title>Structures</title> 1236 <para> 1237 This chapter contains the autogenerated documentation of the structures which are 1238 used in the NAND driver and might be relevant for a driver developer. Each 1239 struct member has a short description which is marked with an [XXX] identifier. 1240 See the chapter "Documentation hints" for an explanation. 1241 </para> 1242!Iinclude/linux/mtd/nand.h 1243 </chapter> 1244 1245 <chapter id="pubfunctions"> 1246 <title>Public Functions Provided</title> 1247 <para> 1248 This chapter contains the autogenerated documentation of the NAND kernel API functions 1249 which are exported. Each function has a short description which is marked with an [XXX] identifier. 1250 See the chapter "Documentation hints" for an explanation. 1251 </para> 1252!Edrivers/mtd/nand/nand_base.c 1253!Edrivers/mtd/nand/nand_bbt.c 1254!Edrivers/mtd/nand/nand_ecc.c 1255 </chapter> 1256 1257 <chapter id="intfunctions"> 1258 <title>Internal Functions Provided</title> 1259 <para> 1260 This chapter contains the autogenerated documentation of the NAND driver internal functions. 1261 Each function has a short description which is marked with an [XXX] identifier. 1262 See the chapter "Documentation hints" for an explanation. 1263 The functions marked with [DEFAULT] might be relevant for a board driver developer. 1264 </para> 1265!Idrivers/mtd/nand/nand_base.c 1266!Idrivers/mtd/nand/nand_bbt.c 1267<!-- No internal functions for kernel-doc: 1268X!Idrivers/mtd/nand/nand_ecc.c 1269--> 1270 </chapter> 1271 1272 <chapter id="credits"> 1273 <title>Credits</title> 1274 <para> 1275 The following people have contributed to the NAND driver: 1276 <orderedlist> 1277 <listitem><para>Steven J. Hill<email>sjhill@realitydiluted.com</email></para></listitem> 1278 <listitem><para>David Woodhouse<email>dwmw2@infradead.org</email></para></listitem> 1279 <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem> 1280 </orderedlist> 1281 A lot of users have provided bugfixes, improvements and helping hands for testing. 1282 Thanks a lot. 1283 </para> 1284 <para> 1285 The following people have contributed to this document: 1286 <orderedlist> 1287 <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem> 1288 </orderedlist> 1289 </para> 1290 </chapter> 1291</book> 1292