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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 replaceable 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 replaceable 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 necessary. 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 &= ~CLE_ADRR_BIT; break;
+ case NAND_CTL_SETALE: this->IO_ADDR_W |= ALE_ADRR_BIT; break;
+ case NAND_CTL_CLRALE: this->IO_ADDR_W &= ~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 necessary
+ 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 necessary 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) &= ~ (1 << 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 &= ~BOARD_NAND_ADDR_MASK;
+ this->IO_ADDR_W &= ~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
+ interfering 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 descriptors 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 necessary 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 protected against
+ accidental access by marking them bad in the memory bad block
+ table. The bad block table management functions are allowed
+ to circumvent 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 necessary 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 bad 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>
+ <spare data page 0><ecc result 0>...<ecc result n>
+ </para>
+ <para>
+ ...
+ </para>
+ <para>
+ <spare data page n><ecc result 0>...<ecc result n>
+ </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 necessary functions for a
+ filesystem via the MTD interface.
+ </para>
+ <para>
+ Filesystems must be aware of the NAND peculiarities 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
+/* 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
+/* Write bbt if necessary */
+#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>
Code Review / kvmfornfv.git / blobdiff