1<?xml version="1.0" encoding="UTF-8"?>
   2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
   3        "" []>
   5<book id="MTD-NAND-Guide">
   6 <bookinfo>
   7  <title>MTD NAND Driver Programming Interface</title>
   9  <authorgroup>
  10   <author>
  11    <firstname>Thomas</firstname>
  12    <surname>Gleixner</surname>
  13    <affiliation>
  14     <address>
  15      <email></email>
  16     </address>
  17    </affiliation>
  18   </author>
  19  </authorgroup>
  21  <copyright>
  22   <year>2004</year>
  23   <holder>Thomas Gleixner</holder>
  24  </copyright>
  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>
  33   <para>
  34     This program is distributed in the hope that it will be
  35     useful, but WITHOUT ANY WARRANTY; without even the implied
  37     See the GNU General Public License for more details.
  38   </para>
  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>
  47   <para>
  48     For more details see the file COPYING in the source
  49     distribution of Linux.
  50   </para>
  51  </legalnotice>
  52 </bookinfo>
  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>
  69  <chapter id="bugs">
  70     <title>Known Bugs And Assumptions</title>
  71  <para>
  72        None.   
  73  </para>
  74  </chapter>
  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 replacable 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 replacable 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 neccecary. 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>   
 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 mtd structure and
 166                        a storage for the ioremap'ed chip address.
 167                        You can allocate the mtd structure using kmalloc
 168                        or you can allocate it statically.
 169                        In case of static allocation you have to allocate
 170                        a nand_chip structure too.
 171                </para>
 172                <para>
 173                        Kmalloc based example
 174                </para>
 175                <programlisting>
 176static struct mtd_info *board_mtd;
 177static void __iomem *baseaddr;
 178                </programlisting>
 179                <para>
 180                        Static example
 181                </para>
 182                <programlisting>
 183static struct mtd_info board_mtd;
 184static struct nand_chip board_chip;
 185static void __iomem *baseaddr;
 186                </programlisting>
 187        </sect1>
 188        <sect1 id="Partition_defines">
 189                <title>Partition defines</title>
 190                <para>
 191                        If you want to divide your device into partitions, then
 192                        define a partitioning scheme suitable to your board.
 193                </para>
 194                <programlisting>
 195#define NUM_PARTITIONS 2
 196static struct mtd_partition partition_info[] = {
 197        { .name = "Flash partition 1",
 198          .offset =  0,
 199          .size =    8 * 1024 * 1024 },
 200        { .name = "Flash partition 2",
 201          .offset =  MTDPART_OFS_NEXT,
 202          .size =    MTDPART_SIZ_FULL },
 204                </programlisting>
 205        </sect1>
 206        <sect1 id="Hardware_control_functions">
 207                <title>Hardware control function</title>
 208                <para>
 209                        The hardware control function provides access to the 
 210                        control pins of the NAND chip(s). 
 211                        The access can be done by GPIO pins or by address lines.
 212                        If you use address lines, make sure that the timing
 213                        requirements are met.
 214                </para>
 215                <para>
 216                        <emphasis>GPIO based example</emphasis>
 217                </para>
 218                <programlisting>
 219static void board_hwcontrol(struct mtd_info *mtd, int cmd)
 221        switch(cmd){
 222                case NAND_CTL_SETCLE: /* Set CLE pin high */ break;
 223                case NAND_CTL_CLRCLE: /* Set CLE pin low */ break;
 224                case NAND_CTL_SETALE: /* Set ALE pin high */ break;
 225                case NAND_CTL_CLRALE: /* Set ALE pin low */ break;
 226                case NAND_CTL_SETNCE: /* Set nCE pin low */ break;
 227                case NAND_CTL_CLRNCE: /* Set nCE pin high */ break;
 228        }
 230                </programlisting>
 231                <para>
 232                        <emphasis>Address lines based example.</emphasis> It's assumed that the
 233                        nCE pin is driven by a chip select decoder.
 234                </para>
 235                <programlisting>
 236static void board_hwcontrol(struct mtd_info *mtd, int cmd)
 238        struct nand_chip *this = (struct nand_chip *) mtd->priv;
 239        switch(cmd){
 240                case NAND_CTL_SETCLE: this->IO_ADDR_W |= CLE_ADRR_BIT;  break;
 241                case NAND_CTL_CLRCLE: this->IO_ADDR_W &amp;= ~CLE_ADRR_BIT; break;
 242                case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT;  break;
 243                case NAND_CTL_CLRALE: this->IO_ADDR_W &amp;= ~ALE_ADRR_BIT; break;
 244        }
 246                </programlisting>
 247        </sect1>
 248        <sect1 id="Device_ready_function">
 249                <title>Device ready function</title>
 250                <para>
 251                        If the hardware interface has the ready busy pin of the NAND chip connected to a
 252                        GPIO or other accessible I/O pin, this function is used to read back the state of the
 253                        pin. The function has no arguments and should return 0, if the device is busy (R/B pin 
 254                        is low) and 1, if the device is ready (R/B pin is high).
 255                        If the hardware interface does not give access to the ready busy pin, then
 256                        the function must not be defined and the function pointer this->dev_ready is set to NULL.               
 257                </para>
 258        </sect1>
 259        <sect1 id="Init_function">
 260                <title>Init function</title>
 261                <para>
 262                        The init function allocates memory and sets up all the board
 263                        specific parameters and function pointers. When everything
 264                        is set up nand_scan() is called. This function tries to
 265                        detect and identify then chip. If a chip is found all the
 266                        internal data fields are initialized accordingly.
 267                        The structure(s) have to be zeroed out first and then filled with the neccecary 
 268                        information about the device.
 269                </para>
 270                <programlisting>
 271static int __init board_init (void)
 273        struct nand_chip *this;
 274        int err = 0;
 276        /* Allocate memory for MTD device structure and private data */
 277        board_mtd = kzalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip), GFP_KERNEL);
 278        if (!board_mtd) {
 279                printk ("Unable to allocate NAND MTD device structure.\n");
 280                err = -ENOMEM;
 281                goto out;
 282        }
 284        /* map physical address */
 285        baseaddr = ioremap(CHIP_PHYSICAL_ADDRESS, 1024);
 286        if (!baseaddr) {
 287                printk("Ioremap to access NAND chip failed\n");
 288                err = -EIO;
 289                goto out_mtd;
 290        }
 292        /* Get pointer to private data */
 293        this = (struct nand_chip *) ();
 294        /* Link the private data with the MTD structure */
 295        board_mtd->priv = this;
 297        /* Set address of NAND IO lines */
 298        this->IO_ADDR_R = baseaddr;
 299        this->IO_ADDR_W = baseaddr;
 300        /* Reference hardware control function */
 301        this->hwcontrol = board_hwcontrol;
 302        /* Set command delay time, see datasheet for correct value */
 303        this->chip_delay = CHIP_DEPENDEND_COMMAND_DELAY;
 304        /* Assign the device ready function, if available */
 305        this->dev_ready = board_dev_ready;
 306        this->eccmode = NAND_ECC_SOFT;
 308        /* Scan to find existence of the device */
 309        if (nand_scan (board_mtd, 1)) {
 310                err = -ENXIO;
 311                goto out_ior;
 312        }
 314        add_mtd_partitions(board_mtd, partition_info, NUM_PARTITIONS);
 315        goto out;
 318        iounmap(baseaddr);
 320        kfree (board_mtd);
 322        return err;
 325                </programlisting>
 326        </sect1>
 327        <sect1 id="Exit_function">
 328                <title>Exit function</title>
 329                <para>
 330                        The exit function is only neccecary if the driver is
 331                        compiled as a module. It releases all resources which
 332                        are held by the chip driver and unregisters the partitions
 333                        in the MTD layer.
 334                </para>
 335                <programlisting>
 336#ifdef MODULE
 337static void __exit board_cleanup (void)
 339        /* Release resources, unregister device */
 340        nand_release (board_mtd);
 342        /* unmap physical address */
 343        iounmap(baseaddr);
 345        /* Free the MTD device structure */
 346        kfree (board_mtd);
 350                </programlisting>
 351        </sect1>
 352  </chapter>
 354  <chapter id="boarddriversadvanced">
 355        <title>Advanced board driver functions</title>
 356        <para>
 357                This chapter describes the advanced functionality of the NAND
 358                driver. For a list of functions which can be overridden by the board
 359                driver see the documentation of the nand_chip structure.
 360        </para>
 361        <sect1 id="Multiple_chip_control">
 362                <title>Multiple chip control</title>
 363                <para>
 364                        The nand driver can control chip arrays. Therefore the
 365                        board driver must provide an own select_chip function. This
 366                        function must (de)select the requested chip.
 367                        The function pointer in the nand_chip structure must
 368                        be set before calling nand_scan(). The maxchip parameter
 369                        of nand_scan() defines the maximum number of chips to
 370                        scan for. Make sure that the select_chip function can
 371                        handle the requested number of chips.
 372                </para>
 373                <para>
 374                        The nand driver concatenates the chips to one virtual
 375                        chip and provides this virtual chip to the MTD layer.
 376                </para>
 377                <para>
 378                        <emphasis>Note: The driver can only handle linear chip arrays
 379                        of equally sized chips. There is no support for
 380                        parallel arrays which extend the buswidth.</emphasis>
 381                </para>
 382                <para>
 383                        <emphasis>GPIO based example</emphasis>
 384                </para>
 385                <programlisting>
 386static void board_select_chip (struct mtd_info *mtd, int chip)
 388        /* Deselect all chips, set all nCE pins high */
 389        GPIO(BOARD_NAND_NCE) |= 0xff;   
 390        if (chip >= 0)
 391                GPIO(BOARD_NAND_NCE) &amp;= ~ (1 &lt;&lt; chip);
 393                </programlisting>
 394                <para>
 395                        <emphasis>Address lines based example.</emphasis>
 396                        Its assumed that the nCE pins are connected to an
 397                        address decoder.
 398                </para>
 399                <programlisting>
 400static void board_select_chip (struct mtd_info *mtd, int chip)
 402        struct nand_chip *this = (struct nand_chip *) mtd->priv;
 404        /* Deselect all chips */
 405        this->IO_ADDR_R &amp;= ~BOARD_NAND_ADDR_MASK;
 406        this->IO_ADDR_W &amp;= ~BOARD_NAND_ADDR_MASK;
 407        switch (chip) {
 408        case 0:
 409                this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIP0;
 410                this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIP0;
 411                break;
 412        ....    
 413        case n:
 414                this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIPn;
 415                this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIPn;
 416                break;
 417        }       
 419                </programlisting>
 420        </sect1>
 421        <sect1 id="Hardware_ECC_support">
 422                <title>Hardware ECC support</title>
 423                <sect2 id="Functions_and_constants">
 424                        <title>Functions and constants</title>
 425                        <para>
 426                                The nand driver supports three different types of
 427                                hardware ECC.
 428                                <itemizedlist>
 429                                <listitem><para>NAND_ECC_HW3_256</para><para>
 430                                Hardware ECC generator providing 3 bytes ECC per
 431                                256 byte.
 432                                </para> </listitem>
 433                                <listitem><para>NAND_ECC_HW3_512</para><para>
 434                                Hardware ECC generator providing 3 bytes ECC per
 435                                512 byte.
 436                                </para> </listitem>
 437                                <listitem><para>NAND_ECC_HW6_512</para><para>
 438                                Hardware ECC generator providing 6 bytes ECC per
 439                                512 byte.
 440                                </para> </listitem>
 441                                <listitem><para>NAND_ECC_HW8_512</para><para>
 442                                Hardware ECC generator providing 6 bytes ECC per
 443                                512 byte.
 444                                </para> </listitem>
 445                                </itemizedlist>
 446                                If your hardware generator has a different functionality
 447                                add it at the appropriate place in nand_base.c
 448                        </para>
 449                        <para>
 450                                The board driver must provide following functions:
 451                                <itemizedlist>
 452                                <listitem><para>enable_hwecc</para><para>
 453                                This function is called before reading / writing to
 454                                the chip. Reset or initialize the hardware generator
 455                                in this function. The function is called with an
 456                                argument which let you distinguish between read 
 457                                and write operations.
 458                                </para> </listitem>
 459                                <listitem><para>calculate_ecc</para><para>
 460                                This function is called after read / write from / to
 461                                the chip. Transfer the ECC from the hardware to
 462                                the buffer. If the option NAND_HWECC_SYNDROME is set
 463                                then the function is only called on write. See below.
 464                                </para> </listitem>
 465                                <listitem><para>correct_data</para><para>
 466                                In case of an ECC error this function is called for
 467                                error detection and correction. Return 1 respectively 2
 468                                in case the error can be corrected. If the error is
 469                                not correctable return -1. If your hardware generator
 470                                matches the default algorithm of the nand_ecc software
 471                                generator then use the correction function provided
 472                                by nand_ecc instead of implementing duplicated code.
 473                                </para> </listitem>
 474                                </itemizedlist>
 475                        </para>
 476                </sect2>
 477                <sect2 id="Hardware_ECC_with_syndrome_calculation">
 478                <title>Hardware ECC with syndrome calculation</title>
 479                        <para>
 480                                Many hardware ECC implementations provide Reed-Solomon
 481                                codes and calculate an error syndrome on read. The syndrome
 482                                must be converted to a standard Reed-Solomon syndrome
 483                                before calling the error correction code in the generic
 484                                Reed-Solomon library.
 485                        </para>
 486                        <para>
 487                                The ECC bytes must be placed immediately after the data
 488                                bytes in order to make the syndrome generator work. This
 489                                is contrary to the usual layout used by software ECC. The
 490                                separation of data and out of band area is not longer
 491                                possible. The nand driver code handles this layout and
 492                                the remaining free bytes in the oob area are managed by 
 493                                the autoplacement code. Provide a matching oob-layout
 494                                in this case. See rts_from4.c and diskonchip.c for 
 495                                implementation reference. In those cases we must also
 496                                use bad block tables on FLASH, because the ECC layout is
 497                                interferring with the bad block marker positions.
 498                                See bad block table support for details.
 499                        </para>
 500                </sect2>
 501        </sect1>
 502        <sect1 id="Bad_Block_table_support">
 503                <title>Bad block table support</title>
 504                <para>
 505                        Most NAND chips mark the bad blocks at a defined
 506                        position in the spare area. Those blocks must 
 507                        not be erased under any circumstances as the bad 
 508                        block information would be lost.
 509                        It is possible to check the bad block mark each
 510                        time when the blocks are accessed by reading the
 511                        spare area of the first page in the block. This
 512                        is time consuming so a bad block table is used.
 513                </para>
 514                <para>
 515                        The nand driver supports various types of bad block
 516                        tables.
 517                        <itemizedlist>
 518                        <listitem><para>Per device</para><para>
 519                        The bad block table contains all bad block information
 520                        of the device which can consist of multiple chips.
 521                        </para> </listitem>
 522                        <listitem><para>Per chip</para><para>
 523                        A bad block table is used per chip and contains the
 524                        bad block information for this particular chip.
 525                        </para> </listitem>
 526                        <listitem><para>Fixed offset</para><para>
 527                        The bad block table is located at a fixed offset
 528                        in the chip (device). This applies to various
 529                        DiskOnChip devices.
 530                        </para> </listitem>
 531                        <listitem><para>Automatic placed</para><para>
 532                        The bad block table is automatically placed and
 533                        detected either at the end or at the beginning
 534                        of a chip (device)
 535                        </para> </listitem>
 536                        <listitem><para>Mirrored tables</para><para>
 537                        The bad block table is mirrored on the chip (device) to
 538                        allow updates of the bad block table without data loss.
 539                        </para> </listitem>
 540                        </itemizedlist>
 541                </para>
 542                <para>  
 543                        nand_scan() calls the function nand_default_bbt(). 
 544                        nand_default_bbt() selects appropriate default
 545                        bad block table desriptors depending on the chip information
 546                        which was retrieved by nand_scan().
 547                </para>
 548                <para>
 549                        The standard policy is scanning the device for bad 
 550                        blocks and build a ram based bad block table which
 551                        allows faster access than always checking the
 552                        bad block information on the flash chip itself.
 553                </para>
 554                <sect2 id="Flash_based_tables">
 555                        <title>Flash based tables</title>
 556                        <para>
 557                                It may be desired or neccecary to keep a bad block table in FLASH. 
 558                                For AG-AND chips this is mandatory, as they have no factory marked
 559                                bad blocks. They have factory marked good blocks. The marker pattern
 560                                is erased when the block is erased to be reused. So in case of
 561                                powerloss before writing the pattern back to the chip this block 
 562                                would be lost and added to the bad blocks. Therefore we scan the 
 563                                chip(s) when we detect them the first time for good blocks and 
 564                                store this information in a bad block table before erasing any 
 565                                of the blocks.
 566                        </para>
 567                        <para>
 568                                The blocks in which the tables are stored are procteted against
 569                                accidental access by marking them bad in the memory bad block
 570                                table. The bad block table management functions are allowed
 571                                to circumvernt this protection.
 572                        </para>
 573                        <para>
 574                                The simplest way to activate the FLASH based bad block table support 
 575                                is to set the option NAND_BBT_USE_FLASH in the bbt_option field of
 576                                the nand chip structure before calling nand_scan(). For AG-AND
 577                                chips is this done by default.
 578                                This activates the default FLASH based bad block table functionality 
 579                                of the NAND driver. The default bad block table options are
 580                                <itemizedlist>
 581                                <listitem><para>Store bad block table per chip</para></listitem>
 582                                <listitem><para>Use 2 bits per block</para></listitem>
 583                                <listitem><para>Automatic placement at the end of the chip</para></listitem>
 584                                <listitem><para>Use mirrored tables with version numbers</para></listitem>
 585                                <listitem><para>Reserve 4 blocks at the end of the chip</para></listitem>
 586                                </itemizedlist>
 587                        </para>
 588                </sect2>
 589                <sect2 id="User_defined_tables">
 590                        <title>User defined tables</title>
 591                        <para>
 592                                User defined tables are created by filling out a 
 593                                nand_bbt_descr structure and storing the pointer in the
 594                                nand_chip structure member bbt_td before calling nand_scan(). 
 595                                If a mirror table is neccecary a second structure must be
 596                                created and a pointer to this structure must be stored
 597                                in bbt_md inside the nand_chip structure. If the bbt_md 
 598                                member is set to NULL then only the main table is used
 599                                and no scan for the mirrored table is performed.
 600                        </para>
 601                        <para>
 602                                The most important field in the nand_bbt_descr structure
 603                                is the options field. The options define most of the 
 604                                table properties. Use the predefined constants from
 605                                nand.h to define the options.
 606                                <itemizedlist>
 607                                <listitem><para>Number of bits per block</para>
 608                                <para>The supported number of bits is 1, 2, 4, 8.</para></listitem>
 609                                <listitem><para>Table per chip</para>
 610                                <para>Setting the constant NAND_BBT_PERCHIP selects that
 611                                a bad block table is managed for each chip in a chip array.
 612                                If this option is not set then a per device bad block table
 613                                is used.</para></listitem>
 614                                <listitem><para>Table location is absolute</para>
 615                                <para>Use the option constant NAND_BBT_ABSPAGE and
 616                                define the absolute page number where the bad block
 617                                table starts in the field pages. If you have selected bad block
 618                                tables per chip and you have a multi chip array then the start page
 619                                must be given for each chip in the chip array. Note: there is no scan
 620                                for a table ident pattern performed, so the fields 
 621                                pattern, veroffs, offs, len can be left uninitialized</para></listitem>
 622                                <listitem><para>Table location is automatically detected</para>
 623                                <para>The table can either be located in the first or the last good
 624                                blocks of the chip (device). Set NAND_BBT_LASTBLOCK to place
 625                                the bad block table at the end of the chip (device). The
 626                                bad block tables are marked and identified by a pattern which
 627                                is stored in the spare area of the first page in the block which
 628                                holds the bad block table. Store a pointer to the pattern  
 629                                in the pattern field. Further the length of the pattern has to be 
 630                                stored in len and the offset in the spare area must be given
 631                                in the offs member of the nand_bbt_descr structure. For mirrored
 632                                bad block tables different patterns are mandatory.</para></listitem>
 633                                <listitem><para>Table creation</para>
 634                                <para>Set the option NAND_BBT_CREATE to enable the table creation
 635                                if no table can be found during the scan. Usually this is done only 
 636                                once if a new chip is found. </para></listitem>
 637                                <listitem><para>Table write support</para>
 638                                <para>Set the option NAND_BBT_WRITE to enable the table write support.
 639                                This allows the update of the bad block table(s) in case a block has
 640                                to be marked bad due to wear. The MTD interface function block_markbad
 641                                is calling the update function of the bad block table. If the write
 642                                support is enabled then the table is updated on FLASH.</para>
 643                                <para>
 644                                Note: Write support should only be enabled for mirrored tables with
 645                                version control.
 646                                </para></listitem>
 647                                <listitem><para>Table version control</para>
 648                                <para>Set the option NAND_BBT_VERSION to enable the table version control.
 649                                It's highly recommended to enable this for mirrored tables with write
 650                                support. It makes sure that the risk of losing the bad block
 651                                table information is reduced to the loss of the information about the
 652                                one worn out block which should be marked bad. The version is stored in
 653                                4 consecutive bytes in the spare area of the device. The position of
 654                                the version number is defined by the member veroffs in the bad block table
 655                                descriptor.</para></listitem>
 656                                <listitem><para>Save block contents on write</para>
 657                                <para>
 658                                In case that the block which holds the bad block table does contain
 659                                other useful information, set the option NAND_BBT_SAVECONTENT. When
 660                                the bad block table is written then the whole block is read the bad
 661                                block table is updated and the block is erased and everything is 
 662                                written back. If this option is not set only the bad block table
 663                                is written and everything else in the block is ignored and erased.
 664                                </para></listitem>
 665                                <listitem><para>Number of reserved blocks</para>
 666                                <para>
 667                                For automatic placement some blocks must be reserved for
 668                                bad block table storage. The number of reserved blocks is defined 
 669                                in the maxblocks member of the babd block table description structure.
 670                                Reserving 4 blocks for mirrored tables should be a reasonable number. 
 671                                This also limits the number of blocks which are scanned for the bad
 672                                block table ident pattern.
 673                                </para></listitem>
 674                                </itemizedlist>
 675                        </para>
 676                </sect2>
 677        </sect1>
 678        <sect1 id="Spare_area_placement">
 679                <title>Spare area (auto)placement</title>
 680                <para>
 681                        The nand driver implements different possibilities for
 682                        placement of filesystem data in the spare area, 
 683                        <itemizedlist>
 684                        <listitem><para>Placement defined by fs driver</para></listitem>
 685                        <listitem><para>Automatic placement</para></listitem>
 686                        </itemizedlist>
 687                        The default placement function is automatic placement. The
 688                        nand driver has built in default placement schemes for the
 689                        various chiptypes. If due to hardware ECC functionality the
 690                        default placement does not fit then the board driver can
 691                        provide a own placement scheme.
 692                </para>
 693                <para>
 694                        File system drivers can provide a own placement scheme which
 695                        is used instead of the default placement scheme.
 696                </para>
 697                <para>
 698                        Placement schemes are defined by a nand_oobinfo structure
 699                        <programlisting>
 700struct nand_oobinfo {
 701        int     useecc;
 702        int     eccbytes;
 703        int     eccpos[24];
 704        int     oobfree[8][2];
 706                        </programlisting>
 707                        <itemizedlist>
 708                        <listitem><para>useecc</para><para>
 709                                The useecc member controls the ecc and placement function. The header
 710                                file include/mtd/mtd-abi.h contains constants to select ecc and
 711                                placement. MTD_NANDECC_OFF switches off the ecc complete. This is
 712                                not recommended and available for testing and diagnosis only.
 713                                MTD_NANDECC_PLACE selects caller defined placement, MTD_NANDECC_AUTOPLACE
 714                                selects automatic placement.
 715                        </para></listitem>
 716                        <listitem><para>eccbytes</para><para>
 717                                The eccbytes member defines the number of ecc bytes per page.
 718                        </para></listitem>
 719                        <listitem><para>eccpos</para><para>
 720                                The eccpos array holds the byte offsets in the spare area where
 721                                the ecc codes are placed.
 722                        </para></listitem>
 723                        <listitem><para>oobfree</para><para>
 724                                The oobfree array defines the areas in the spare area which can be
 725                                used for automatic placement. The information is given in the format
 726                                {offset, size}. offset defines the start of the usable area, size the
 727                                length in bytes. More than one area can be defined. The list is terminated
 728                                by an {0, 0} entry.
 729                        </para></listitem>
 730                        </itemizedlist>
 731                </para>
 732                <sect2 id="Placement_defined_by_fs_driver">
 733                        <title>Placement defined by fs driver</title>
 734                        <para>
 735                                The calling function provides a pointer to a nand_oobinfo
 736                                structure which defines the ecc placement. For writes the
 737                                caller must provide a spare area buffer along with the
 738                                data buffer. The spare area buffer size is (number of pages) *
 739                                (size of spare area). For reads the buffer size is
 740                                (number of pages) * ((size of spare area) + (number of ecc
 741                                steps per page) * sizeof (int)). The driver stores the
 742                                result of the ecc check for each tuple in the spare buffer.
 743                                The storage sequence is 
 744                        </para>
 745                        <para>
 746                                &lt;spare data page 0&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
 747                        </para>
 748                        <para>
 749                                ...
 750                        </para>
 751                        <para>
 752                                &lt;spare data page n&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
 753                        </para>
 754                        <para>
 755                                This is a legacy mode used by YAFFS1.
 756                        </para>
 757                        <para>
 758                                If the spare area buffer is NULL then only the ECC placement is
 759                                done according to the given scheme in the nand_oobinfo structure.
 760                        </para>
 761                </sect2>
 762                <sect2 id="Automatic_placement">
 763                        <title>Automatic placement</title>
 764                        <para>
 765                                Automatic placement uses the built in defaults to place the
 766                                ecc bytes in the spare area. If filesystem data have to be stored /
 767                                read into the spare area then the calling function must provide a
 768                                buffer. The buffer size per page is determined by the oobfree array in
 769                                the nand_oobinfo structure.
 770                        </para>
 771                        <para>
 772                                If the spare area buffer is NULL then only the ECC placement is
 773                                done according to the default builtin scheme.
 774                        </para>
 775                </sect2>
 776        </sect1>        
 777        <sect1 id="Spare_area_autoplacement_default">
 778                <title>Spare area autoplacement default schemes</title>
 779                <sect2 id="pagesize_256">
 780                        <title>256 byte pagesize</title>
 781<informaltable><tgroup cols="3"><tbody>
 789<entry>ECC byte 0</entry>
 790<entry>Error correction code byte 0</entry>
 794<entry>ECC byte 1</entry>
 795<entry>Error correction code byte 1</entry>
 799<entry>ECC byte 2</entry>
 800<entry>Error correction code byte 2</entry>
 804<entry>Autoplace 0</entry>
 809<entry>Autoplace 1</entry>
 814<entry>Bad block marker</entry>
 815<entry>If any bit in this byte is zero, then this block is bad.
 816This applies only to the first page in a block. In the remaining
 817pages this byte is reserved</entry>
 821<entry>Autoplace 2</entry>
 826<entry>Autoplace 3</entry>
 830                </sect2>
 831                <sect2 id="pagesize_512">
 832                        <title>512 byte pagesize</title>
 833<informaltable><tgroup cols="3"><tbody>
 841<entry>ECC byte 0</entry>
 842<entry>Error correction code byte 0 of the lower 256 Byte data in
 843this page</entry>
 847<entry>ECC byte 1</entry>
 848<entry>Error correction code byte 1 of the lower 256 Bytes of data
 849in this page</entry>
 853<entry>ECC byte 2</entry>
 854<entry>Error correction code byte 2 of the lower 256 Bytes of data
 855in this page</entry>
 859<entry>ECC byte 3</entry>
 860<entry>Error correction code byte 0 of the upper 256 Bytes of data
 861in this page</entry>
 870<entry>Bad block marker</entry>
 871<entry>If any bit in this byte is zero, then this block is bad.
 872This applies only to the first page in a block. In the remaining
 873pages this byte is reserved</entry>
 877<entry>ECC byte 4</entry>
 878<entry>Error correction code byte 1 of the upper 256 Bytes of data
 879in this page</entry>
 883<entry>ECC byte 5</entry>
 884<entry>Error correction code byte 2 of the upper 256 Bytes of data
 885in this page</entry>
 888<entry>0x08 - 0x0F</entry>
 889<entry>Autoplace 0 - 7</entry>
 893                </sect2>
 894                <sect2 id="pagesize_2048">
 895                        <title>2048 byte pagesize</title>
 896<informaltable><tgroup cols="3"><tbody>
 904<entry>Bad block marker</entry>
 905<entry>If any bit in this byte is zero, then this block is bad.
 906This applies only to the first page in a block. In the remaining
 907pages this byte is reserved</entry>
 916<entry>Autoplace 0 - 37</entry>
 921<entry>ECC byte 0</entry>
 922<entry>Error correction code byte 0 of the first 256 Byte data in
 923this page</entry>
 927<entry>ECC byte 1</entry>
 928<entry>Error correction code byte 1 of the first 256 Bytes of data
 929in this page</entry>
 933<entry>ECC byte 2</entry>
 934<entry>Error correction code byte 2 of the first 256 Bytes data in
 935this page</entry>
 939<entry>ECC byte 3</entry>
 940<entry>Error correction code byte 0 of the second 256 Bytes of data
 941in this page</entry>
 945<entry>ECC byte 4</entry>
 946<entry>Error correction code byte 1 of the second 256 Bytes of data
 947in this page</entry>
 951<entry>ECC byte 5</entry>
 952<entry>Error correction code byte 2 of the second 256 Bytes of data
 953in this page</entry>
 957<entry>ECC byte 6</entry>
 958<entry>Error correction code byte 0 of the third 256 Bytes of data
 959in this page</entry>
 963<entry>ECC byte 7</entry>
 964<entry>Error correction code byte 1 of the third 256 Bytes of data
 965in this page</entry>
 969<entry>ECC byte 8</entry>
 970<entry>Error correction code byte 2 of the third 256 Bytes of data
 971in this page</entry>
 975<entry>ECC byte 9</entry>
 976<entry>Error correction code byte 0 of the fourth 256 Bytes of data
 977in this page</entry>
 981<entry>ECC byte 10</entry>
 982<entry>Error correction code byte 1 of the fourth 256 Bytes of data
 983in this page</entry>
 987<entry>ECC byte 11</entry>
 988<entry>Error correction code byte 2 of the fourth 256 Bytes of data
 989in this page</entry>
 993<entry>ECC byte 12</entry>
 994<entry>Error correction code byte 0 of the fifth 256 Bytes of data
 995in this page</entry>
 999<entry>ECC byte 13</entry>
1000<entry>Error correction code byte 1 of the fifth 256 Bytes of data
1001in this page</entry>
1005<entry>ECC byte 14</entry>
1006<entry>Error correction code byte 2 of the fifth 256 Bytes of data
1007in this page</entry>
1011<entry>ECC byte 15</entry>
1012<entry>Error correction code byte 0 of the sixt 256 Bytes of data
1013in this page</entry>
1017<entry>ECC byte 16</entry>
1018<entry>Error correction code byte 1 of the sixt 256 Bytes of data
1019in this page</entry>
1023<entry>ECC byte 17</entry>
1024<entry>Error correction code byte 2 of the sixt 256 Bytes of data
1025in this page</entry>
1029<entry>ECC byte 18</entry>
1030<entry>Error correction code byte 0 of the seventh 256 Bytes of
1031data in this page</entry>
1035<entry>ECC byte 19</entry>
1036<entry>Error correction code byte 1 of the seventh 256 Bytes of
1037data in this page</entry>
1041<entry>ECC byte 20</entry>
1042<entry>Error correction code byte 2 of the seventh 256 Bytes of
1043data in this page</entry>
1047<entry>ECC byte 21</entry>
1048<entry>Error correction code byte 0 of the eighth 256 Bytes of data
1049in this page</entry>
1053<entry>ECC byte 22</entry>
1054<entry>Error correction code byte 1 of the eighth 256 Bytes of data
1055in this page</entry>
1059<entry>ECC byte 23</entry>
1060<entry>Error correction code byte 2 of the eighth 256 Bytes of data
1061in this page</entry>
1064                </sect2>
1065        </sect1>
1066  </chapter>
1068  <chapter id="filesystems">
1069        <title>Filesystem support</title>
1070        <para>
1071                The NAND driver provides all neccecary functions for a
1072                filesystem via the MTD interface.
1073        </para>
1074        <para>
1075                Filesystems must be aware of the NAND pecularities and
1076                restrictions. One major restrictions of NAND Flash is, that you cannot 
1077                write as often as you want to a page. The consecutive writes to a page, 
1078                before erasing it again, are restricted to 1-3 writes, depending on the 
1079                manufacturers specifications. This applies similar to the spare area. 
1080        </para>
1081        <para>
1082                Therefore NAND aware filesystems must either write in page size chunks
1083                or hold a writebuffer to collect smaller writes until they sum up to 
1084                pagesize. Available NAND aware filesystems: JFFS2, YAFFS.               
1085        </para>
1086        <para>
1087                The spare area usage to store filesystem data is controlled by
1088                the spare area placement functionality which is described in one
1089                of the earlier chapters.
1090        </para>
1091  </chapter>    
1092  <chapter id="tools">
1093        <title>Tools</title>
1094        <para>
1095                The MTD project provides a couple of helpful tools to handle NAND Flash.
1096                <itemizedlist>
1097                <listitem><para>flasherase, flasheraseall: Erase and format FLASH partitions</para></listitem>
1098                <listitem><para>nandwrite: write filesystem images to NAND FLASH</para></listitem>
1099                <listitem><para>nanddump: dump the contents of a NAND FLASH partitions</para></listitem>
1100                </itemizedlist>
1101        </para>
1102        <para>
1103                These tools are aware of the NAND restrictions. Please use those tools
1104                instead of complaining about errors which are caused by non NAND aware
1105                access methods.
1106        </para>
1107  </chapter>    
1109  <chapter id="defines">
1110     <title>Constants</title>
1111     <para>
1112     This chapter describes the constants which might be relevant for a driver developer.
1113     </para>
1114     <sect1 id="Chip_option_constants">
1115        <title>Chip option constants</title>
1116        <sect2 id="Constants_for_chip_id_table">
1117                <title>Constants for chip id table</title>
1118                <para>
1119                These constants are defined in nand.h. They are ored together to describe
1120                the chip functionality.
1121                <programlisting>
1122/* Buswitdh is 16 bit */
1123#define NAND_BUSWIDTH_16        0x00000002
1124/* Device supports partial programming without padding */
1125#define NAND_NO_PADDING         0x00000004
1126/* Chip has cache program function */
1127#define NAND_CACHEPRG           0x00000008
1128/* Chip has copy back function */
1129#define NAND_COPYBACK           0x00000010
1130/* AND Chip which has 4 banks and a confusing page / block 
1131 * assignment. See Renesas datasheet for further information */
1132#define NAND_IS_AND             0x00000020
1133/* Chip has a array of 4 pages which can be read without
1134 * additional ready /busy waits */
1135#define NAND_4PAGE_ARRAY        0x00000040 
1136                </programlisting>
1137                </para>
1138        </sect2>
1139        <sect2 id="Constants_for_runtime_options">
1140                <title>Constants for runtime options</title>
1141                <para>
1142                These constants are defined in nand.h. They are ored together to describe
1143                the functionality.
1144                <programlisting>
1145/* The hw ecc generator provides a syndrome instead a ecc value on read 
1146 * This can only work if we have the ecc bytes directly behind the 
1147 * data bytes. Applies for DOC and AG-AND Renesas HW Reed Solomon generators */
1148#define NAND_HWECC_SYNDROME     0x00020000
1149                </programlisting>
1150                </para>
1151        </sect2>
1152     </sect1>   
1154     <sect1 id="EEC_selection_constants">
1155        <title>ECC selection constants</title>
1156        <para>
1157        Use these constants to select the ECC algorithm.
1158        <programlisting>
1159/* No ECC. Usage is not recommended ! */
1160#define NAND_ECC_NONE           0
1161/* Software ECC 3 byte ECC per 256 Byte data */
1162#define NAND_ECC_SOFT           1
1163/* Hardware ECC 3 byte ECC per 256 Byte data */
1164#define NAND_ECC_HW3_256        2
1165/* Hardware ECC 3 byte ECC per 512 Byte data */
1166#define NAND_ECC_HW3_512        3
1167/* Hardware ECC 6 byte ECC per 512 Byte data */
1168#define NAND_ECC_HW6_512        4
1169/* Hardware ECC 6 byte ECC per 512 Byte data */
1170#define NAND_ECC_HW8_512        6
1171        </programlisting>
1172        </para>
1173     </sect1>   
1175     <sect1 id="Hardware_control_related_constants">
1176        <title>Hardware control related constants</title>
1177        <para>
1178        These constants describe the requested hardware access function when
1179        the boardspecific hardware control function is called
1180        <programlisting>
1181/* Select the chip by setting nCE to low */
1182#define NAND_CTL_SETNCE         1
1183/* Deselect the chip by setting nCE to high */
1184#define NAND_CTL_CLRNCE         2
1185/* Select the command latch by setting CLE to high */
1186#define NAND_CTL_SETCLE         3
1187/* Deselect the command latch by setting CLE to low */
1188#define NAND_CTL_CLRCLE         4
1189/* Select the address latch by setting ALE to high */
1190#define NAND_CTL_SETALE         5
1191/* Deselect the address latch by setting ALE to low */
1192#define NAND_CTL_CLRALE         6
1193/* Set write protection by setting WP to high. Not used! */
1194#define NAND_CTL_SETWP          7
1195/* Clear write protection by setting WP to low. Not used! */
1196#define NAND_CTL_CLRWP          8
1197        </programlisting>
1198        </para>
1199     </sect1>   
1201     <sect1 id="Bad_block_table_constants">
1202        <title>Bad block table related constants</title>
1203        <para>
1204        These constants describe the options used for bad block
1205        table descriptors.
1206        <programlisting>
1207/* Options for the bad block table descriptors */
1209/* The number of bits used per block in the bbt on the device */
1210#define NAND_BBT_NRBITS_MSK     0x0000000F
1211#define NAND_BBT_1BIT           0x00000001
1212#define NAND_BBT_2BIT           0x00000002
1213#define NAND_BBT_4BIT           0x00000004
1214#define NAND_BBT_8BIT           0x00000008
1215/* The bad block table is in the last good block of the device */
1216#define NAND_BBT_LASTBLOCK      0x00000010
1217/* The bbt is at the given page, else we must scan for the bbt */
1218#define NAND_BBT_ABSPAGE        0x00000020
1219/* The bbt is at the given page, else we must scan for the bbt */
1220#define NAND_BBT_SEARCH         0x00000040
1221/* bbt is stored per chip on multichip devices */
1222#define NAND_BBT_PERCHIP        0x00000080
1223/* bbt has a version counter at offset veroffs */
1224#define NAND_BBT_VERSION        0x00000100
1225/* Create a bbt if none axists */
1226#define NAND_BBT_CREATE         0x00000200
1227/* Search good / bad pattern through all pages of a block */
1228#define NAND_BBT_SCANALLPAGES   0x00000400
1229/* Scan block empty during good / bad block scan */
1230#define NAND_BBT_SCANEMPTY      0x00000800
1231/* Write bbt if neccecary */
1232#define NAND_BBT_WRITE          0x00001000
1233/* Read and write back block contents when writing bbt */
1234#define NAND_BBT_SAVECONTENT    0x00002000
1235        </programlisting>
1236        </para>
1237     </sect1>   
1239  </chapter>
1241  <chapter id="structs">
1242     <title>Structures</title>
1243     <para>
1244     This chapter contains the autogenerated documentation of the structures which are
1245     used in the NAND driver and might be relevant for a driver developer. Each  
1246     struct member has a short description which is marked with an [XXX] identifier.
1247     See the chapter "Documentation hints" for an explanation.
1248     </para>
1250  </chapter>
1252  <chapter id="pubfunctions">
1253     <title>Public Functions Provided</title>
1254     <para>
1255     This chapter contains the autogenerated documentation of the NAND kernel API functions
1256      which are exported. Each function has a short description which is marked with an [XXX] identifier.
1257     See the chapter "Documentation hints" for an explanation.
1258     </para>
1262  </chapter>
1264  <chapter id="intfunctions">
1265     <title>Internal Functions Provided</title>
1266     <para>
1267     This chapter contains the autogenerated documentation of the NAND driver internal functions.
1268     Each function has a short description which is marked with an [XXX] identifier.
1269     See the chapter "Documentation hints" for an explanation.
1270     The functions marked with [DEFAULT] might be relevant for a board driver developer.
1271     </para>
1274<!-- No internal functions for kernel-doc:
1277  </chapter>
1279  <chapter id="credits">
1280     <title>Credits</title>
1281        <para>
1282                The following people have contributed to the NAND driver:
1283                <orderedlist>
1284                        <listitem><para>Steven J. Hill<email></email></para></listitem>
1285                        <listitem><para>David Woodhouse<email></email></para></listitem>
1286                        <listitem><para>Thomas Gleixner<email></email></para></listitem>
1287                </orderedlist>
1288                A lot of users have provided bugfixes, improvements and helping hands for testing.
1289                Thanks a lot.
1290        </para>
1291        <para>
1292                The following people have contributed to this document:
1293                <orderedlist>
1294                        <listitem><para>Thomas Gleixner<email></email></para></listitem>
1295                </orderedlist>
1296        </para>
1297  </chapter>
1299 kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.