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-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
-
-<book id="MTD-NAND-Guide">
- <bookinfo>
- <title>MTD NAND Driver Programming Interface</title>
-
- <authorgroup>
- <author>
- <firstname>Thomas</firstname>
- <surname>Gleixner</surname>
- <affiliation>
- <address>
- <email>tglx@linutronix.de</email>
- </address>
- </affiliation>
- </author>
- </authorgroup>
-
- <copyright>
- <year>2004</year>
- <holder>Thomas Gleixner</holder>
- </copyright>
-
- <legalnotice>
- <para>
- This documentation is free software; you can redistribute
- it and/or modify it under the terms of the GNU General Public
- License version 2 as published by the Free Software Foundation.
- </para>
-
- <para>
- This program is distributed in the hope that it will be
- useful, but WITHOUT ANY WARRANTY; without even the implied
- warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
- See the GNU General Public License for more details.
- </para>
-
- <para>
- You should have received a copy of the GNU General Public
- License along with this program; if not, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
- MA 02111-1307 USA
- </para>
-
- <para>
- For more details see the file COPYING in the source
- distribution of Linux.
- </para>
- </legalnotice>
- </bookinfo>
-
-<toc></toc>
-
- <chapter id="intro">
- <title>Introduction</title>
- <para>
- The generic NAND driver supports almost all NAND and AG-AND based
- chips and connects them to the Memory Technology Devices (MTD)
- subsystem of the Linux Kernel.
- </para>
- <para>
- This documentation is provided for developers who want to implement
- board drivers or filesystem drivers suitable for NAND devices.
- </para>
- </chapter>
-
- <chapter id="bugs">
- <title>Known Bugs And Assumptions</title>
- <para>
- None.
- </para>
- </chapter>
-
- <chapter id="dochints">
- <title>Documentation hints</title>
- <para>
- The function and structure docs are autogenerated. Each function and
- struct member has a short description which is marked with an [XXX] identifier.
- The following chapters explain the meaning of those identifiers.
- </para>
- <sect1 id="Function_identifiers_XXX">
- <title>Function identifiers [XXX]</title>
- <para>
- The functions are marked with [XXX] identifiers in the short
- comment. The identifiers explain the usage and scope of the
- functions. Following identifiers are used:
- </para>
- <itemizedlist>
- <listitem><para>
- [MTD Interface]</para><para>
- These functions provide the interface to the MTD kernel API.
- They are not replacable and provide functionality
- which is complete hardware independent.
- </para></listitem>
- <listitem><para>
- [NAND Interface]</para><para>
- These functions are exported and provide the interface to the NAND kernel API.
- </para></listitem>
- <listitem><para>
- [GENERIC]</para><para>
- Generic functions are not replacable and provide functionality
- which is complete hardware independent.
- </para></listitem>
- <listitem><para>
- [DEFAULT]</para><para>
- Default functions provide hardware related functionality which is suitable
- for most of the implementations. These functions can be replaced by the
- board driver if neccecary. Those functions are called via pointers in the
- NAND chip description structure. The board driver can set the functions which
- should be replaced by board dependent functions before calling nand_scan().
- If the function pointer is NULL on entry to nand_scan() then the pointer
- is set to the default function which is suitable for the detected chip type.
- </para></listitem>
- </itemizedlist>
- </sect1>
- <sect1 id="Struct_member_identifiers_XXX">
- <title>Struct member identifiers [XXX]</title>
- <para>
- The struct members are marked with [XXX] identifiers in the
- comment. The identifiers explain the usage and scope of the
- members. Following identifiers are used:
- </para>
- <itemizedlist>
- <listitem><para>
- [INTERN]</para><para>
- These members are for NAND driver internal use only and must not be
- modified. Most of these values are calculated from the chip geometry
- information which is evaluated during nand_scan().
- </para></listitem>
- <listitem><para>
- [REPLACEABLE]</para><para>
- Replaceable members hold hardware related functions which can be
- provided by the board driver. The board driver can set the functions which
- should be replaced by board dependent functions before calling nand_scan().
- If the function pointer is NULL on entry to nand_scan() then the pointer
- is set to the default function which is suitable for the detected chip type.
- </para></listitem>
- <listitem><para>
- [BOARDSPECIFIC]</para><para>
- Board specific members hold hardware related information which must
- be provided by the board driver. The board driver must set the function
- pointers and datafields before calling nand_scan().
- </para></listitem>
- <listitem><para>
- [OPTIONAL]</para><para>
- Optional members can hold information relevant for the board driver. The
- generic NAND driver code does not use this information.
- </para></listitem>
- </itemizedlist>
- </sect1>
- </chapter>
-
- <chapter id="basicboarddriver">
- <title>Basic board driver</title>
- <para>
- For most boards it will be sufficient to provide just the
- basic functions and fill out some really board dependent
- members in the nand chip description structure.
- </para>
- <sect1 id="Basic_defines">
- <title>Basic defines</title>
- <para>
- At least you have to provide a mtd structure and
- a storage for the ioremap'ed chip address.
- You can allocate the mtd structure using kmalloc
- or you can allocate it statically.
- In case of static allocation you have to allocate
- a nand_chip structure too.
- </para>
- <para>
- Kmalloc based example
- </para>
- <programlisting>
-static struct mtd_info *board_mtd;
-static void __iomem *baseaddr;
- </programlisting>
- <para>
- Static example
- </para>
- <programlisting>
-static struct mtd_info board_mtd;
-static struct nand_chip board_chip;
-static void __iomem *baseaddr;
- </programlisting>
- </sect1>
- <sect1 id="Partition_defines">
- <title>Partition defines</title>
- <para>
- If you want to divide your device into partitions, then
- define a partitioning scheme suitable to your board.
- </para>
- <programlisting>
-#define NUM_PARTITIONS 2
-static struct mtd_partition partition_info[] = {
- { .name = "Flash partition 1",
- .offset = 0,
- .size = 8 * 1024 * 1024 },
- { .name = "Flash partition 2",
- .offset = MTDPART_OFS_NEXT,
- .size = MTDPART_SIZ_FULL },
-};
- </programlisting>
- </sect1>
- <sect1 id="Hardware_control_functions">
- <title>Hardware control function</title>
- <para>
- The hardware control function provides access to the
- control pins of the NAND chip(s).
- The access can be done by GPIO pins or by address lines.
- If you use address lines, make sure that the timing
- requirements are met.
- </para>
- <para>
- <emphasis>GPIO based example</emphasis>
- </para>
- <programlisting>
-static void board_hwcontrol(struct mtd_info *mtd, int cmd)
-{
- switch(cmd){
- case NAND_CTL_SETCLE: /* Set CLE pin high */ break;
- case NAND_CTL_CLRCLE: /* Set CLE pin low */ break;
- case NAND_CTL_SETALE: /* Set ALE pin high */ break;
- case NAND_CTL_CLRALE: /* Set ALE pin low */ break;
- case NAND_CTL_SETNCE: /* Set nCE pin low */ break;
- case NAND_CTL_CLRNCE: /* Set nCE pin high */ break;
- }
-}
- </programlisting>
- <para>
- <emphasis>Address lines based example.</emphasis> It's assumed that the
- nCE pin is driven by a chip select decoder.
- </para>
- <programlisting>
-static void board_hwcontrol(struct mtd_info *mtd, int cmd)
-{
- struct nand_chip *this = (struct nand_chip *) mtd->priv;
- switch(cmd){
- case NAND_CTL_SETCLE: this->IO_ADDR_W |= CLE_ADRR_BIT; break;
- case NAND_CTL_CLRCLE: this->IO_ADDR_W &amp;= ~CLE_ADRR_BIT; break;
- case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT; break;
- case NAND_CTL_CLRALE: this->IO_ADDR_W &amp;= ~ALE_ADRR_BIT; break;
- }
-}
- </programlisting>
- </sect1>
- <sect1 id="Device_ready_function">
- <title>Device ready function</title>
- <para>
- If the hardware interface has the ready busy pin of the NAND chip connected to a
- GPIO or other accessible I/O pin, this function is used to read back the state of the
- pin. The function has no arguments and should return 0, if the device is busy (R/B pin
- is low) and 1, if the device is ready (R/B pin is high).
- If the hardware interface does not give access to the ready busy pin, then
- the function must not be defined and the function pointer this->dev_ready is set to NULL.
- </para>
- </sect1>
- <sect1 id="Init_function">
- <title>Init function</title>
- <para>
- The init function allocates memory and sets up all the board
- specific parameters and function pointers. When everything
- is set up nand_scan() is called. This function tries to
- detect and identify then chip. If a chip is found all the
- internal data fields are initialized accordingly.
- The structure(s) have to be zeroed out first and then filled with the neccecary
- information about the device.
- </para>
- <programlisting>
-static int __init board_init (void)
-{
- struct nand_chip *this;
- int err = 0;
-
- /* Allocate memory for MTD device structure and private data */
- board_mtd = kzalloc(sizeof(struct mtd_info) + sizeof(struct nand_chip), GFP_KERNEL);
- if (!board_mtd) {
- printk ("Unable to allocate NAND MTD device structure.\n");
- err = -ENOMEM;
- goto out;
- }
-
- /* map physical address */
- baseaddr = ioremap(CHIP_PHYSICAL_ADDRESS, 1024);
- if (!baseaddr) {
- printk("Ioremap to access NAND chip failed\n");
- err = -EIO;
- goto out_mtd;
- }
-
- /* Get pointer to private data */
- this = (struct nand_chip *) ();
- /* Link the private data with the MTD structure */
- board_mtd->priv = this;
-
- /* Set address of NAND IO lines */
- this->IO_ADDR_R = baseaddr;
- this->IO_ADDR_W = baseaddr;
- /* Reference hardware control function */
- this->hwcontrol = board_hwcontrol;
- /* Set command delay time, see datasheet for correct value */
- this->chip_delay = CHIP_DEPENDEND_COMMAND_DELAY;
- /* Assign the device ready function, if available */
- this->dev_ready = board_dev_ready;
- this->eccmode = NAND_ECC_SOFT;
-
- /* Scan to find existence of the device */
- if (nand_scan (board_mtd, 1)) {
- err = -ENXIO;
- goto out_ior;
- }
-
- add_mtd_partitions(board_mtd, partition_info, NUM_PARTITIONS);
- goto out;
-
-out_ior:
- iounmap(baseaddr);
-out_mtd:
- kfree (board_mtd);
-out:
- return err;
-}
-module_init(board_init);
- </programlisting>
- </sect1>
- <sect1 id="Exit_function">
- <title>Exit function</title>
- <para>
- The exit function is only neccecary if the driver is
- compiled as a module. It releases all resources which
- are held by the chip driver and unregisters the partitions
- in the MTD layer.
- </para>
- <programlisting>
-#ifdef MODULE
-static void __exit board_cleanup (void)
-{
- /* Release resources, unregister device */
- nand_release (board_mtd);
-
- /* unmap physical address */
- iounmap(baseaddr);
-
- /* Free the MTD device structure */
- kfree (board_mtd);
-}
-module_exit(board_cleanup);
-#endif
- </programlisting>
- </sect1>
- </chapter>
-
- <chapter id="boarddriversadvanced">
- <title>Advanced board driver functions</title>
- <para>
- This chapter describes the advanced functionality of the NAND
- driver. For a list of functions which can be overridden by the board
- driver see the documentation of the nand_chip structure.
- </para>
- <sect1 id="Multiple_chip_control">
- <title>Multiple chip control</title>
- <para>
- The nand driver can control chip arrays. Therefore the
- board driver must provide an own select_chip function. This
- function must (de)select the requested chip.
- The function pointer in the nand_chip structure must
- be set before calling nand_scan(). The maxchip parameter
- of nand_scan() defines the maximum number of chips to
- scan for. Make sure that the select_chip function can
- handle the requested number of chips.
- </para>
- <para>
- The nand driver concatenates the chips to one virtual
- chip and provides this virtual chip to the MTD layer.
- </para>
- <para>
- <emphasis>Note: The driver can only handle linear chip arrays
- of equally sized chips. There is no support for
- parallel arrays which extend the buswidth.</emphasis>
- </para>
- <para>
- <emphasis>GPIO based example</emphasis>
- </para>
- <programlisting>
-static void board_select_chip (struct mtd_info *mtd, int chip)
-{
- /* Deselect all chips, set all nCE pins high */
- GPIO(BOARD_NAND_NCE) |= 0xff;
- if (chip >= 0)
- GPIO(BOARD_NAND_NCE) &amp;= ~ (1 &lt;&lt; chip);
-}
- </programlisting>
- <para>
- <emphasis>Address lines based example.</emphasis>
- Its assumed that the nCE pins are connected to an
- address decoder.
- </para>
- <programlisting>
-static void board_select_chip (struct mtd_info *mtd, int chip)
-{
- struct nand_chip *this = (struct nand_chip *) mtd->priv;
-
- /* Deselect all chips */
- this->IO_ADDR_R &amp;= ~BOARD_NAND_ADDR_MASK;
- this->IO_ADDR_W &amp;= ~BOARD_NAND_ADDR_MASK;
- switch (chip) {
- case 0:
- this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIP0;
- this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIP0;
- break;
- ....
- case n:
- this->IO_ADDR_R |= BOARD_NAND_ADDR_CHIPn;
- this->IO_ADDR_W |= BOARD_NAND_ADDR_CHIPn;
- break;
- }
-}
- </programlisting>
- </sect1>
- <sect1 id="Hardware_ECC_support">
- <title>Hardware ECC support</title>
- <sect2 id="Functions_and_constants">
- <title>Functions and constants</title>
- <para>
- The nand driver supports three different types of
- hardware ECC.
- <itemizedlist>
- <listitem><para>NAND_ECC_HW3_256</para><para>
- Hardware ECC generator providing 3 bytes ECC per
- 256 byte.
- </para> </listitem>
- <listitem><para>NAND_ECC_HW3_512</para><para>
- Hardware ECC generator providing 3 bytes ECC per
- 512 byte.
- </para> </listitem>
- <listitem><para>NAND_ECC_HW6_512</para><para>
- Hardware ECC generator providing 6 bytes ECC per
- 512 byte.
- </para> </listitem>
- <listitem><para>NAND_ECC_HW8_512</para><para>
- Hardware ECC generator providing 6 bytes ECC per
- 512 byte.
- </para> </listitem>
- </itemizedlist>
- If your hardware generator has a different functionality
- add it at the appropriate place in nand_base.c
- </para>
- <para>
- The board driver must provide following functions:
- <itemizedlist>
- <listitem><para>enable_hwecc</para><para>
- This function is called before reading / writing to
- the chip. Reset or initialize the hardware generator
- in this function. The function is called with an
- argument which let you distinguish between read
- and write operations.
- </para> </listitem>
- <listitem><para>calculate_ecc</para><para>
- This function is called after read / write from / to
- the chip. Transfer the ECC from the hardware to
- the buffer. If the option NAND_HWECC_SYNDROME is set
- then the function is only called on write. See below.
- </para> </listitem>
- <listitem><para>correct_data</para><para>
- In case of an ECC error this function is called for
- error detection and correction. Return 1 respectively 2
- in case the error can be corrected. If the error is
- not correctable return -1. If your hardware generator
- matches the default algorithm of the nand_ecc software
- generator then use the correction function provided
- by nand_ecc instead of implementing duplicated code.
- </para> </listitem>
- </itemizedlist>
- </para>
- </sect2>
- <sect2 id="Hardware_ECC_with_syndrome_calculation">
- <title>Hardware ECC with syndrome calculation</title>
- <para>
- Many hardware ECC implementations provide Reed-Solomon
- codes and calculate an error syndrome on read. The syndrome
- must be converted to a standard Reed-Solomon syndrome
- before calling the error correction code in the generic
- Reed-Solomon library.
- </para>
- <para>
- The ECC bytes must be placed immediately after the data
- bytes in order to make the syndrome generator work. This
- is contrary to the usual layout used by software ECC. The
- separation of data and out of band area is not longer
- possible. The nand driver code handles this layout and
- the remaining free bytes in the oob area are managed by
- the autoplacement code. Provide a matching oob-layout
- in this case. See rts_from4.c and diskonchip.c for
- implementation reference. In those cases we must also
- use bad block tables on FLASH, because the ECC layout is
- interferring with the bad block marker positions.
- See bad block table support for details.
- </para>
- </sect2>
- </sect1>
- <sect1 id="Bad_Block_table_support">
- <title>Bad block table support</title>
- <para>
- Most NAND chips mark the bad blocks at a defined
- position in the spare area. Those blocks must
- not be erased under any circumstances as the bad
- block information would be lost.
- It is possible to check the bad block mark each
- time when the blocks are accessed by reading the
- spare area of the first page in the block. This
- is time consuming so a bad block table is used.
- </para>
- <para>
- The nand driver supports various types of bad block
- tables.
- <itemizedlist>
- <listitem><para>Per device</para><para>
- The bad block table contains all bad block information
- of the device which can consist of multiple chips.
- </para> </listitem>
- <listitem><para>Per chip</para><para>
- A bad block table is used per chip and contains the
- bad block information for this particular chip.
- </para> </listitem>
- <listitem><para>Fixed offset</para><para>
- The bad block table is located at a fixed offset
- in the chip (device). This applies to various
- DiskOnChip devices.
- </para> </listitem>
- <listitem><para>Automatic placed</para><para>
- The bad block table is automatically placed and
- detected either at the end or at the beginning
- of a chip (device)
- </para> </listitem>
- <listitem><para>Mirrored tables</para><para>
- The bad block table is mirrored on the chip (device) to
- allow updates of the bad block table without data loss.
- </para> </listitem>
- </itemizedlist>
- </para>
- <para>
- nand_scan() calls the function nand_default_bbt().
- nand_default_bbt() selects appropriate default
- bad block table desriptors depending on the chip information
- which was retrieved by nand_scan().
- </para>
- <para>
- The standard policy is scanning the device for bad
- blocks and build a ram based bad block table which
- allows faster access than always checking the
- bad block information on the flash chip itself.
- </para>
- <sect2 id="Flash_based_tables">
- <title>Flash based tables</title>
- <para>
- It may be desired or neccecary to keep a bad block table in FLASH.
- For AG-AND chips this is mandatory, as they have no factory marked
- bad blocks. They have factory marked good blocks. The marker pattern
- is erased when the block is erased to be reused. So in case of
- powerloss before writing the pattern back to the chip this block
- would be lost and added to the bad blocks. Therefore we scan the
- chip(s) when we detect them the first time for good blocks and
- store this information in a bad block table before erasing any
- of the blocks.
- </para>
- <para>
- The blocks in which the tables are stored are procteted against
- accidental access by marking them bad in the memory bad block
- table. The bad block table management functions are allowed
- to circumvernt this protection.
- </para>
- <para>
- The simplest way to activate the FLASH based bad block table support
- is to set the option NAND_BBT_USE_FLASH in the bbt_option field of
- the nand chip structure before calling nand_scan(). For AG-AND
- chips is this done by default.
- This activates the default FLASH based bad block table functionality
- of the NAND driver. The default bad block table options are
- <itemizedlist>
- <listitem><para>Store bad block table per chip</para></listitem>
- <listitem><para>Use 2 bits per block</para></listitem>
- <listitem><para>Automatic placement at the end of the chip</para></listitem>
- <listitem><para>Use mirrored tables with version numbers</para></listitem>
- <listitem><para>Reserve 4 blocks at the end of the chip</para></listitem>
- </itemizedlist>
- </para>
- </sect2>
- <sect2 id="User_defined_tables">
- <title>User defined tables</title>
- <para>
- User defined tables are created by filling out a
- nand_bbt_descr structure and storing the pointer in the
- nand_chip structure member bbt_td before calling nand_scan().
- If a mirror table is neccecary a second structure must be
- created and a pointer to this structure must be stored
- in bbt_md inside the nand_chip structure. If the bbt_md
- member is set to NULL then only the main table is used
- and no scan for the mirrored table is performed.
- </para>
- <para>
- The most important field in the nand_bbt_descr structure
- is the options field. The options define most of the
- table properties. Use the predefined constants from
- nand.h to define the options.
- <itemizedlist>
- <listitem><para>Number of bits per block</para>
- <para>The supported number of bits is 1, 2, 4, 8.</para></listitem>
- <listitem><para>Table per chip</para>
- <para>Setting the constant NAND_BBT_PERCHIP selects that
- a bad block table is managed for each chip in a chip array.
- If this option is not set then a per device bad block table
- is used.</para></listitem>
- <listitem><para>Table location is absolute</para>
- <para>Use the option constant NAND_BBT_ABSPAGE and
- define the absolute page number where the bad block
- table starts in the field pages. If you have selected bad block
- tables per chip and you have a multi chip array then the start page
- must be given for each chip in the chip array. Note: there is no scan
- for a table ident pattern performed, so the fields
- pattern, veroffs, offs, len can be left uninitialized</para></listitem>
- <listitem><para>Table location is automatically detected</para>
- <para>The table can either be located in the first or the last good
- blocks of the chip (device). Set NAND_BBT_LASTBLOCK to place
- the bad block table at the end of the chip (device). The
- bad block tables are marked and identified by a pattern which
- is stored in the spare area of the first page in the block which
- holds the bad block table. Store a pointer to the pattern
- in the pattern field. Further the length of the pattern has to be
- stored in len and the offset in the spare area must be given
- in the offs member of the nand_bbt_descr structure. For mirrored
- bad block tables different patterns are mandatory.</para></listitem>
- <listitem><para>Table creation</para>
- <para>Set the option NAND_BBT_CREATE to enable the table creation
- if no table can be found during the scan. Usually this is done only
- once if a new chip is found. </para></listitem>
- <listitem><para>Table write support</para>
- <para>Set the option NAND_BBT_WRITE to enable the table write support.
- This allows the update of the bad block table(s) in case a block has
- to be marked bad due to wear. The MTD interface function block_markbad
- is calling the update function of the bad block table. If the write
- support is enabled then the table is updated on FLASH.</para>
- <para>
- Note: Write support should only be enabled for mirrored tables with
- version control.
- </para></listitem>
- <listitem><para>Table version control</para>
- <para>Set the option NAND_BBT_VERSION to enable the table version control.
- It's highly recommended to enable this for mirrored tables with write
- support. It makes sure that the risk of losing the bad block
- table information is reduced to the loss of the information about the
- one worn out block which should be marked bad. The version is stored in
- 4 consecutive bytes in the spare area of the device. The position of
- the version number is defined by the member veroffs in the bad block table
- descriptor.</para></listitem>
- <listitem><para>Save block contents on write</para>
- <para>
- In case that the block which holds the bad block table does contain
- other useful information, set the option NAND_BBT_SAVECONTENT. When
- the bad block table is written then the whole block is read the bad
- block table is updated and the block is erased and everything is
- written back. If this option is not set only the bad block table
- is written and everything else in the block is ignored and erased.
- </para></listitem>
- <listitem><para>Number of reserved blocks</para>
- <para>
- For automatic placement some blocks must be reserved for
- bad block table storage. The number of reserved blocks is defined
- in the maxblocks member of the babd block table description structure.
- Reserving 4 blocks for mirrored tables should be a reasonable number.
- This also limits the number of blocks which are scanned for the bad
- block table ident pattern.
- </para></listitem>
- </itemizedlist>
- </para>
- </sect2>
- </sect1>
- <sect1 id="Spare_area_placement">
- <title>Spare area (auto)placement</title>
- <para>
- The nand driver implements different possibilities for
- placement of filesystem data in the spare area,
- <itemizedlist>
- <listitem><para>Placement defined by fs driver</para></listitem>
- <listitem><para>Automatic placement</para></listitem>
- </itemizedlist>
- The default placement function is automatic placement. The
- nand driver has built in default placement schemes for the
- various chiptypes. If due to hardware ECC functionality the
- default placement does not fit then the board driver can
- provide a own placement scheme.
- </para>
- <para>
- File system drivers can provide a own placement scheme which
- is used instead of the default placement scheme.
- </para>
- <para>
- Placement schemes are defined by a nand_oobinfo structure
- <programlisting>
-struct nand_oobinfo {
- int useecc;
- int eccbytes;
- int eccpos[24];
- int oobfree[8][2];
-};
- </programlisting>
- <itemizedlist>
- <listitem><para>useecc</para><para>
- The useecc member controls the ecc and placement function. The header
- file include/mtd/mtd-abi.h contains constants to select ecc and
- placement. MTD_NANDECC_OFF switches off the ecc complete. This is
- not recommended and available for testing and diagnosis only.
- MTD_NANDECC_PLACE selects caller defined placement, MTD_NANDECC_AUTOPLACE
- selects automatic placement.
- </para></listitem>
- <listitem><para>eccbytes</para><para>
- The eccbytes member defines the number of ecc bytes per page.
- </para></listitem>
- <listitem><para>eccpos</para><para>
- The eccpos array holds the byte offsets in the spare area where
- the ecc codes are placed.
- </para></listitem>
- <listitem><para>oobfree</para><para>
- The oobfree array defines the areas in the spare area which can be
- used for automatic placement. The information is given in the format
- {offset, size}. offset defines the start of the usable area, size the
- length in bytes. More than one area can be defined. The list is terminated
- by an {0, 0} entry.
- </para></listitem>
- </itemizedlist>
- </para>
- <sect2 id="Placement_defined_by_fs_driver">
- <title>Placement defined by fs driver</title>
- <para>
- The calling function provides a pointer to a nand_oobinfo
- structure which defines the ecc placement. For writes the
- caller must provide a spare area buffer along with the
- data buffer. The spare area buffer size is (number of pages) *
- (size of spare area). For reads the buffer size is
- (number of pages) * ((size of spare area) + (number of ecc
- steps per page) * sizeof (int)). The driver stores the
- result of the ecc check for each tuple in the spare buffer.
- The storage sequence is
- </para>
- <para>
- &lt;spare data page 0&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
- </para>
- <para>
- ...
- </para>
- <para>
- &lt;spare data page n&gt;&lt;ecc result 0&gt;...&lt;ecc result n&gt;
- </para>
- <para>
- This is a legacy mode used by YAFFS1.
- </para>
- <para>
- If the spare area buffer is NULL then only the ECC placement is
- done according to the given scheme in the nand_oobinfo structure.
- </para>
- </sect2>
- <sect2 id="Automatic_placement">
- <title>Automatic placement</title>
- <para>
- Automatic placement uses the built in defaults to place the
- ecc bytes in the spare area. If filesystem data have to be stored /
- read into the spare area then the calling function must provide a
- buffer. The buffer size per page is determined by the oobfree array in
- the nand_oobinfo structure.
- </para>
- <para>
- If the spare area buffer is NULL then only the ECC placement is
- done according to the default builtin scheme.
- </para>
- </sect2>
- </sect1>
- <sect1 id="Spare_area_autoplacement_default">
- <title>Spare area autoplacement default schemes</title>
- <sect2 id="pagesize_256">
- <title>256 byte pagesize</title>
-<informaltable><tgroup cols="3"><tbody>
-<row>
-<entry>Offset</entry>
-<entry>Content</entry>
-<entry>Comment</entry>
-</row>
-<row>
-<entry>0x00</entry>
-<entry>ECC byte 0</entry>
-<entry>Error correction code byte 0</entry>
-</row>
-<row>
-<entry>0x01</entry>
-<entry>ECC byte 1</entry>
-<entry>Error correction code byte 1</entry>
-</row>
-<row>
-<entry>0x02</entry>
-<entry>ECC byte 2</entry>
-<entry>Error correction code byte 2</entry>
-</row>
-<row>
-<entry>0x03</entry>
-<entry>Autoplace 0</entry>
-<entry></entry>
-</row>
-<row>
-<entry>0x04</entry>
-<entry>Autoplace 1</entry>
-<entry></entry>
-</row>
-<row>
-<entry>0x05</entry>
-<entry>Bad block marker</entry>
-<entry>If any bit in this byte is zero, then this block is bad.
-This applies only to the first page in a block. In the remaining
-pages this byte is reserved</entry>
-</row>
-<row>
-<entry>0x06</entry>
-<entry>Autoplace 2</entry>
-<entry></entry>
-</row>
-<row>
-<entry>0x07</entry>
-<entry>Autoplace 3</entry>
-<entry></entry>
-</row>
-</tbody></tgroup></informaltable>
- </sect2>
- <sect2 id="pagesize_512">
- <title>512 byte pagesize</title>
-<informaltable><tgroup cols="3"><tbody>
-<row>
-<entry>Offset</entry>
-<entry>Content</entry>
-<entry>Comment</entry>
-</row>
-<row>
-<entry>0x00</entry>
-<entry>ECC byte 0</entry>
-<entry>Error correction code byte 0 of the lower 256 Byte data in
-this page</entry>
-</row>
-<row>
-<entry>0x01</entry>
-<entry>ECC byte 1</entry>
-<entry>Error correction code byte 1 of the lower 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x02</entry>
-<entry>ECC byte 2</entry>
-<entry>Error correction code byte 2 of the lower 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x03</entry>
-<entry>ECC byte 3</entry>
-<entry>Error correction code byte 0 of the upper 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x04</entry>
-<entry>reserved</entry>
-<entry>reserved</entry>
-</row>
-<row>
-<entry>0x05</entry>
-<entry>Bad block marker</entry>
-<entry>If any bit in this byte is zero, then this block is bad.
-This applies only to the first page in a block. In the remaining
-pages this byte is reserved</entry>
-</row>
-<row>
-<entry>0x06</entry>
-<entry>ECC byte 4</entry>
-<entry>Error correction code byte 1 of the upper 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x07</entry>
-<entry>ECC byte 5</entry>
-<entry>Error correction code byte 2 of the upper 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x08 - 0x0F</entry>
-<entry>Autoplace 0 - 7</entry>
-<entry></entry>
-</row>
-</tbody></tgroup></informaltable>
- </sect2>
- <sect2 id="pagesize_2048">
- <title>2048 byte pagesize</title>
-<informaltable><tgroup cols="3"><tbody>
-<row>
-<entry>Offset</entry>
-<entry>Content</entry>
-<entry>Comment</entry>
-</row>
-<row>
-<entry>0x00</entry>
-<entry>Bad block marker</entry>
-<entry>If any bit in this byte is zero, then this block is bad.
-This applies only to the first page in a block. In the remaining
-pages this byte is reserved</entry>
-</row>
-<row>
-<entry>0x01</entry>
-<entry>Reserved</entry>
-<entry>Reserved</entry>
-</row>
-<row>
-<entry>0x02-0x27</entry>
-<entry>Autoplace 0 - 37</entry>
-<entry></entry>
-</row>
-<row>
-<entry>0x28</entry>
-<entry>ECC byte 0</entry>
-<entry>Error correction code byte 0 of the first 256 Byte data in
-this page</entry>
-</row>
-<row>
-<entry>0x29</entry>
-<entry>ECC byte 1</entry>
-<entry>Error correction code byte 1 of the first 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x2A</entry>
-<entry>ECC byte 2</entry>
-<entry>Error correction code byte 2 of the first 256 Bytes data in
-this page</entry>
-</row>
-<row>
-<entry>0x2B</entry>
-<entry>ECC byte 3</entry>
-<entry>Error correction code byte 0 of the second 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x2C</entry>
-<entry>ECC byte 4</entry>
-<entry>Error correction code byte 1 of the second 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x2D</entry>
-<entry>ECC byte 5</entry>
-<entry>Error correction code byte 2 of the second 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x2E</entry>
-<entry>ECC byte 6</entry>
-<entry>Error correction code byte 0 of the third 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x2F</entry>
-<entry>ECC byte 7</entry>
-<entry>Error correction code byte 1 of the third 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x30</entry>
-<entry>ECC byte 8</entry>
-<entry>Error correction code byte 2 of the third 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x31</entry>
-<entry>ECC byte 9</entry>
-<entry>Error correction code byte 0 of the fourth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x32</entry>
-<entry>ECC byte 10</entry>
-<entry>Error correction code byte 1 of the fourth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x33</entry>
-<entry>ECC byte 11</entry>
-<entry>Error correction code byte 2 of the fourth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x34</entry>
-<entry>ECC byte 12</entry>
-<entry>Error correction code byte 0 of the fifth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x35</entry>
-<entry>ECC byte 13</entry>
-<entry>Error correction code byte 1 of the fifth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x36</entry>
-<entry>ECC byte 14</entry>
-<entry>Error correction code byte 2 of the fifth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x37</entry>
-<entry>ECC byte 15</entry>
-<entry>Error correction code byte 0 of the sixt 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x38</entry>
-<entry>ECC byte 16</entry>
-<entry>Error correction code byte 1 of the sixt 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x39</entry>
-<entry>ECC byte 17</entry>
-<entry>Error correction code byte 2 of the sixt 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x3A</entry>
-<entry>ECC byte 18</entry>
-<entry>Error correction code byte 0 of the seventh 256 Bytes of
-data in this page</entry>
-</row>
-<row>
-<entry>0x3B</entry>
-<entry>ECC byte 19</entry>
-<entry>Error correction code byte 1 of the seventh 256 Bytes of
-data in this page</entry>
-</row>
-<row>
-<entry>0x3C</entry>
-<entry>ECC byte 20</entry>
-<entry>Error correction code byte 2 of the seventh 256 Bytes of
-data in this page</entry>
-</row>
-<row>
-<entry>0x3D</entry>
-<entry>ECC byte 21</entry>
-<entry>Error correction code byte 0 of the eighth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x3E</entry>
-<entry>ECC byte 22</entry>
-<entry>Error correction code byte 1 of the eighth 256 Bytes of data
-in this page</entry>
-</row>
-<row>
-<entry>0x3F</entry>
-<entry>ECC byte 23</entry>
-<entry>Error correction code byte 2 of the eighth 256 Bytes of data
-in this page</entry>
-</row>
-</tbody></tgroup></informaltable>
- </sect2>
- </sect1>
- </chapter>
-
- <chapter id="filesystems">
- <title>Filesystem support</title>
- <para>
- The NAND driver provides all neccecary functions for a
- filesystem via the MTD interface.
- </para>
- <para>
- Filesystems must be aware of the NAND pecularities and
- restrictions. One major restrictions of NAND Flash is, that you cannot
- write as often as you want to a page. The consecutive writes to a page,
- before erasing it again, are restricted to 1-3 writes, depending on the
- manufacturers specifications. This applies similar to the spare area.
- </para>
- <para>
- Therefore NAND aware filesystems must either write in page size chunks
- or hold a writebuffer to collect smaller writes until they sum up to
- pagesize. Available NAND aware filesystems: JFFS2, YAFFS.
- </para>
- <para>
- The spare area usage to store filesystem data is controlled by
- the spare area placement functionality which is described in one
- of the earlier chapters.
- </para>
- </chapter>
- <chapter id="tools">
- <title>Tools</title>
- <para>
- The MTD project provides a couple of helpful tools to handle NAND Flash.
- <itemizedlist>
- <listitem><para>flasherase, flasheraseall: Erase and format FLASH partitions</para></listitem>
- <listitem><para>nandwrite: write filesystem images to NAND FLASH</para></listitem>
- <listitem><para>nanddump: dump the contents of a NAND FLASH partitions</para></listitem>
- </itemizedlist>
- </para>
- <para>
- These tools are aware of the NAND restrictions. Please use those tools
- instead of complaining about errors which are caused by non NAND aware
- access methods.
- </para>
- </chapter>
-
- <chapter id="defines">
- <title>Constants</title>
- <para>
- This chapter describes the constants which might be relevant for a driver developer.
- </para>
- <sect1 id="Chip_option_constants">
- <title>Chip option constants</title>
- <sect2 id="Constants_for_chip_id_table">
- <title>Constants for chip id table</title>
- <para>
- These constants are defined in nand.h. They are ored together to describe
- the chip functionality.
- <programlisting>
-/* Buswitdh is 16 bit */
-#define NAND_BUSWIDTH_16 0x00000002
-/* Device supports partial programming without padding */
-#define NAND_NO_PADDING 0x00000004
-/* Chip has cache program function */
-#define NAND_CACHEPRG 0x00000008
-/* Chip has copy back function */
-#define NAND_COPYBACK 0x00000010
-/* AND Chip which has 4 banks and a confusing page / block
- * assignment. See Renesas datasheet for further information */
-#define NAND_IS_AND 0x00000020
-/* Chip has a array of 4 pages which can be read without
- * additional ready /busy waits */
-#define NAND_4PAGE_ARRAY 0x00000040
- </programlisting>
- </para>
- </sect2>
- <sect2 id="Constants_for_runtime_options">
- <title>Constants for runtime options</title>
- <para>
- These constants are defined in nand.h. They are ored together to describe
- the functionality.
- <programlisting>
-/* The hw ecc generator provides a syndrome instead a ecc value on read
- * This can only work if we have the ecc bytes directly behind the
- * data bytes. Applies for DOC and AG-AND Renesas HW Reed Solomon generators */
-#define NAND_HWECC_SYNDROME 0x00020000
- </programlisting>
- </para>
- </sect2>
- </sect1>
-
- <sect1 id="EEC_selection_constants">
- <title>ECC selection constants</title>
- <para>
- Use these constants to select the ECC algorithm.
- <programlisting>
-/* No ECC. Usage is not recommended ! */
-#define NAND_ECC_NONE 0
-/* Software ECC 3 byte ECC per 256 Byte data */
-#define NAND_ECC_SOFT 1
-/* Hardware ECC 3 byte ECC per 256 Byte data */
-#define NAND_ECC_HW3_256 2
-/* Hardware ECC 3 byte ECC per 512 Byte data */
-#define NAND_ECC_HW3_512 3
-/* Hardware ECC 6 byte ECC per 512 Byte data */
-#define NAND_ECC_HW6_512 4
-/* Hardware ECC 6 byte ECC per 512 Byte data */
-#define NAND_ECC_HW8_512 6
- </programlisting>
- </para>
- </sect1>
-
- <sect1 id="Hardware_control_related_constants">
- <title>Hardware control related constants</title>
- <para>
- These constants describe the requested hardware access function when
- the boardspecific hardware control function is called
- <programlisting>
-/* Select the chip by setting nCE to low */
-#define NAND_CTL_SETNCE 1
-/* Deselect the chip by setting nCE to high */
-#define NAND_CTL_CLRNCE 2
-/* Select the command latch by setting CLE to high */
-#define NAND_CTL_SETCLE 3
-/* Deselect the command latch by setting CLE to low */
-#define NAND_CTL_CLRCLE 4
-/* Select the address latch by setting ALE to high */
-#define NAND_CTL_SETALE 5
-/* Deselect the address latch by setting ALE to low */
-#define NAND_CTL_CLRALE 6
-/* Set write protection by setting WP to high. Not used! */
-#define NAND_CTL_SETWP 7
-/* Clear write protection by setting WP to low. Not used! */
-#define NAND_CTL_CLRWP 8
- </programlisting>
- </para>
- </sect1>
-
- <sect1 id="Bad_block_table_constants">
- <title>Bad block table related constants</title>
- <para>
- These constants describe the options used for bad block
- table descriptors.
- <programlisting>
-/* Options for the bad block table descriptors */
-
-/* The number of bits used per block in the bbt on the device */
-#define NAND_BBT_NRBITS_MSK 0x0000000F
-#define NAND_BBT_1BIT 0x00000001
-#define NAND_BBT_2BIT 0x00000002
-#define NAND_BBT_4BIT 0x00000004
-#define NAND_BBT_8BIT 0x00000008
-/* The bad block table is in the last good block of the device */
-#define NAND_BBT_LASTBLOCK 0x00000010
-/* The bbt is at the given page, else we must scan for the bbt */
-#define NAND_BBT_ABSPAGE 0x00000020
-/* The bbt is at the given page, else we must scan for the bbt */
-#define NAND_BBT_SEARCH 0x00000040
-/* bbt is stored per chip on multichip devices */
-#define NAND_BBT_PERCHIP 0x00000080
-/* bbt has a version counter at offset veroffs */
-#define NAND_BBT_VERSION 0x00000100
-/* Create a bbt if none axists */
-#define NAND_BBT_CREATE 0x00000200
-/* Search good / bad pattern through all pages of a block */
-#define NAND_BBT_SCANALLPAGES 0x00000400
-/* Scan block empty during good / bad block scan */
-#define NAND_BBT_SCANEMPTY 0x00000800
-/* Write bbt if neccecary */
-#define NAND_BBT_WRITE 0x00001000
-/* Read and write back block contents when writing bbt */
-#define NAND_BBT_SAVECONTENT 0x00002000
- </programlisting>
- </para>
- </sect1>
-
- </chapter>
-
- <chapter id="structs">
- <title>Structures</title>
- <para>
- This chapter contains the autogenerated documentation of the structures which are
- used in the NAND driver and might be relevant for a driver developer. Each
- struct member has a short description which is marked with an [XXX] identifier.
- See the chapter "Documentation hints" for an explanation.
- </para>
-!Iinclude/linux/mtd/nand.h
- </chapter>
-
- <chapter id="pubfunctions">
- <title>Public Functions Provided</title>
- <para>
- This chapter contains the autogenerated documentation of the NAND kernel API functions
- which are exported. Each function has a short description which is marked with an [XXX] identifier.
- See the chapter "Documentation hints" for an explanation.
- </para>
-!Edrivers/mtd/nand/nand_base.c
-!Edrivers/mtd/nand/nand_bbt.c
-!Edrivers/mtd/nand/nand_ecc.c
- </chapter>
-
- <chapter id="intfunctions">
- <title>Internal Functions Provided</title>
- <para>
- This chapter contains the autogenerated documentation of the NAND driver internal functions.
- Each function has a short description which is marked with an [XXX] identifier.
- See the chapter "Documentation hints" for an explanation.
- The functions marked with [DEFAULT] might be relevant for a board driver developer.
- </para>
-!Idrivers/mtd/nand/nand_base.c
-!Idrivers/mtd/nand/nand_bbt.c
-<!-- No internal functions for kernel-doc:
-X!Idrivers/mtd/nand/nand_ecc.c
--->
- </chapter>
-
- <chapter id="credits">
- <title>Credits</title>
- <para>
- The following people have contributed to the NAND driver:
- <orderedlist>
- <listitem><para>Steven J. Hill<email>sjhill@realitydiluted.com</email></para></listitem>
- <listitem><para>David Woodhouse<email>dwmw2@infradead.org</email></para></listitem>
- <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem>
- </orderedlist>
- A lot of users have provided bugfixes, improvements and helping hands for testing.
- Thanks a lot.
- </para>
- <para>
- The following people have contributed to this document:
- <orderedlist>
- <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem>
- </orderedlist>
- </para>
- </chapter>
-</book>