352 lines
14 KiB
Plaintext
352 lines
14 KiB
Plaintext
NAND FLASH commands and notes
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See NOTE below!!!
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# (C) Copyright 2003
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# Dave Ellis, SIXNET, dge@sixnetio.com
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#
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# SPDX-License-Identifier: GPL-2.0+
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Commands:
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nand bad
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Print a list of all of the bad blocks in the current device.
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nand device
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Print information about the current NAND device.
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nand device num
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Make device `num' the current device and print information about it.
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nand erase off|partition size
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nand erase clean [off|partition size]
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Erase `size' bytes starting at offset `off'. Alternatively partition
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name can be specified, in this case size will be eventually limited
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to not exceed partition size (this behaviour applies also to read
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and write commands). Only complete erase blocks can be erased.
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If `erase' is specified without an offset or size, the entire flash
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is erased. If `erase' is specified with partition but without an
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size, the entire partition is erased.
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If `clean' is specified, a JFFS2-style clean marker is written to
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each block after it is erased.
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This command will not erase blocks that are marked bad. There is
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a debug option in cmd_nand.c to allow bad blocks to be erased.
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Please read the warning there before using it, as blocks marked
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bad by the manufacturer must _NEVER_ be erased.
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nand info
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Print information about all of the NAND devices found.
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nand read addr ofs|partition size
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Read `size' bytes from `ofs' in NAND flash to `addr'. Blocks that
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are marked bad are skipped. If a page cannot be read because an
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uncorrectable data error is found, the command stops with an error.
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nand read.oob addr ofs|partition size
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Read `size' bytes from the out-of-band data area corresponding to
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`ofs' in NAND flash to `addr'. This is limited to the 16 bytes of
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data for one 512-byte page or 2 256-byte pages. There is no check
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for bad blocks or ECC errors.
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nand write addr ofs|partition size
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Write `size' bytes from `addr' to `ofs' in NAND flash. Blocks that
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are marked bad are skipped. If a page cannot be read because an
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uncorrectable data error is found, the command stops with an error.
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As JFFS2 skips blocks similarly, this allows writing a JFFS2 image,
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as long as the image is short enough to fit even after skipping the
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bad blocks. Compact images, such as those produced by mkfs.jffs2
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should work well, but loading an image copied from another flash is
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going to be trouble if there are any bad blocks.
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nand write.trimffs addr ofs|partition size
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Enabled by the CONFIG_CMD_NAND_TRIMFFS macro. This command will write to
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the NAND flash in a manner identical to the 'nand write' command
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described above -- with the additional check that all pages at the end
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of eraseblocks which contain only 0xff data will not be written to the
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NAND flash. This behaviour is required when flashing UBI images
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containing UBIFS volumes as per the UBI FAQ[1].
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[1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo
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nand write.oob addr ofs|partition size
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Write `size' bytes from `addr' to the out-of-band data area
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corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
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of data for one 512-byte page or 2 256-byte pages. There is no check
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for bad blocks.
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nand read.raw addr ofs|partition [count]
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nand write.raw addr ofs|partition [count]
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Read or write one or more pages at "ofs" in NAND flash, from or to
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"addr" in memory. This is a raw access, so ECC is avoided and the
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OOB area is transferred as well. If count is absent, it is assumed
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to be one page. As with .yaffs2 accesses, the data is formatted as
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a packed sequence of "data, oob, data, oob, ..." -- no alignment of
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individual pages is maintained.
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Configuration Options:
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CONFIG_SYS_NAND_U_BOOT_OFFS
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NAND Offset from where SPL will read u-boot image. This is the starting
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address of u-boot MTD partition in NAND.
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CONFIG_CMD_NAND
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Enables NAND support and commands.
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CONFIG_CMD_NAND_TORTURE
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Enables the torture command (see description of this command below).
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CONFIG_SYS_MAX_NAND_DEVICE
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The maximum number of NAND devices you want to support.
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CONFIG_SYS_NAND_MAX_ECCPOS
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If specified, overrides the maximum number of ECC bytes
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supported. Useful for reducing image size, especially with SPL.
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This must be at least 48 if nand_base.c is used.
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CONFIG_SYS_NAND_MAX_OOBFREE
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If specified, overrides the maximum number of free OOB regions
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supported. Useful for reducing image size, especially with SPL.
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This must be at least 2 if nand_base.c is used.
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CONFIG_SYS_NAND_MAX_CHIPS
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The maximum number of NAND chips per device to be supported.
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CONFIG_SYS_NAND_SELF_INIT
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Traditionally, glue code in drivers/mtd/nand/nand.c has driven
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the initialization process -- it provides the mtd and nand
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structs, calls a board init function for a specific device,
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calls nand_scan(), and registers with mtd.
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This arrangement does not provide drivers with the flexibility to
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run code between nand_scan_ident() and nand_scan_tail(), or other
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deviations from the "normal" flow.
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If a board defines CONFIG_SYS_NAND_SELF_INIT, drivers/mtd/nand/nand.c
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will make one call to board_nand_init(), with no arguments. That
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function is responsible for calling a driver init function for
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each NAND device on the board, that performs all initialization
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tasks except setting mtd->name, and registering with the rest of
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U-Boot. Those last tasks are accomplished by calling nand_register()
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on the new mtd device.
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Example of new init to be added to the end of an existing driver
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init:
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/* chip is struct nand_chip, and is now provided by the driver. */
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mtd = nand_to_mtd(&chip);
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/*
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* Fill in appropriate values if this driver uses these fields,
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* or uses the standard read_byte/write_buf/etc. functions from
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* nand_base.c that use these fields.
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*/
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chip.IO_ADDR_R = ...;
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chip.IO_ADDR_W = ...;
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if (nand_scan_ident(mtd, CONFIG_SYS_MAX_NAND_CHIPS, NULL))
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error out
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/*
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* Insert here any code you wish to run after the chip has been
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* identified, but before any other I/O is done.
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*/
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if (nand_scan_tail(mtd))
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error out
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/*
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* devnum is the device number to be used in nand commands
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* and in mtd->name. Must be less than CONFIG_SYS_MAX_NAND_DEVICE.
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*/
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if (nand_register(devnum, mtd))
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error out
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In addition to providing more flexibility to the driver, it reduces
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the difference between a U-Boot driver and its Linux counterpart.
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nand_init() is now reduced to calling board_nand_init() once, and
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printing a size summary. This should also make it easier to
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transition to delayed NAND initialization.
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Please convert your driver even if you don't need the extra
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flexibility, so that one day we can eliminate the old mechanism.
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CONFIG_SYS_NAND_ONFI_DETECTION
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Enables detection of ONFI compliant devices during probe.
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And fetching device parameters flashed on device, by parsing
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ONFI parameter page.
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CONFIG_BCH
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Enables software based BCH ECC algorithm present in lib/bch.c
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This is used by SoC platforms which do not have built-in ELM
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hardware engine required for BCH ECC correction.
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Platform specific options
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=========================
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CONFIG_NAND_OMAP_GPMC
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Enables omap_gpmc.c driver for OMAPx and AMxxxx platforms.
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GPMC controller is used for parallel NAND flash devices, and can
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do ECC calculation (not ECC error detection) for HAM1, BCH4, BCH8
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and BCH16 ECC algorithms.
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CONFIG_NAND_OMAP_ELM
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Enables omap_elm.c driver for OMAPx and AMxxxx platforms.
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ELM controller is used for ECC error detection (not ECC calculation)
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of BCH4, BCH8 and BCH16 ECC algorithms.
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Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
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thus such SoC platforms need to depend on software library for ECC error
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detection. However ECC calculation on such plaforms would still be
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done by GPMC controller.
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CONFIG_SPL_NAND_AM33XX_BCH
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Enables SPL-NAND driver (am335x_spl_bch.c) which supports ELM based
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hardware ECC correction. This is useful for platforms which have ELM
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hardware engine and use NAND boot mode.
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Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
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so those platforms should use CONFIG_SPL_NAND_SIMPLE for enabling
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SPL-NAND driver with software ECC correction support.
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CONFIG_NAND_OMAP_ECCSCHEME
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On OMAP platforms, this CONFIG specifies NAND ECC scheme.
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It can take following values:
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OMAP_ECC_HAM1_CODE_SW
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1-bit Hamming code using software lib.
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(for legacy devices only)
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OMAP_ECC_HAM1_CODE_HW
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1-bit Hamming code using GPMC hardware.
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(for legacy devices only)
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OMAP_ECC_BCH4_CODE_HW_DETECTION_SW
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4-bit BCH code (unsupported)
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OMAP_ECC_BCH4_CODE_HW
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4-bit BCH code (unsupported)
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OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
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8-bit BCH code with
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- ecc calculation using GPMC hardware engine,
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- error detection using software library.
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- requires CONFIG_BCH to enable software BCH library
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(For legacy device which do not have ELM h/w engine)
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OMAP_ECC_BCH8_CODE_HW
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8-bit BCH code with
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- ecc calculation using GPMC hardware engine,
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- error detection using ELM hardware engine.
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OMAP_ECC_BCH16_CODE_HW
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16-bit BCH code with
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- ecc calculation using GPMC hardware engine,
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- error detection using ELM hardware engine.
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How to select ECC scheme on OMAP and AMxx platforms ?
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-----------------------------------------------------
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Though higher ECC schemes have more capability to detect and correct
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bit-flips, but still selection of ECC scheme is dependent on following
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- hardware engines present in SoC.
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Some legacy OMAP SoC do not have ELM h/w engine thus such
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SoC cannot support BCHx_HW ECC schemes.
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- size of OOB/Spare region
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With higher ECC schemes, more OOB/Spare area is required to
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store ECC. So choice of ECC scheme is limited by NAND oobsize.
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In general following expression can help:
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NAND_OOBSIZE >= 2 + (NAND_PAGESIZE / 512) * ECC_BYTES
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where
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NAND_OOBSIZE = number of bytes available in
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OOB/spare area per NAND page.
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NAND_PAGESIZE = bytes in main-area of NAND page.
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ECC_BYTES = number of ECC bytes generated to
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protect 512 bytes of data, which is:
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3 for HAM1_xx ecc schemes
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7 for BCH4_xx ecc schemes
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14 for BCH8_xx ecc schemes
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26 for BCH16_xx ecc schemes
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example to check for BCH16 on 2K page NAND
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NAND_PAGESIZE = 2048
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NAND_OOBSIZE = 64
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2 + (2048 / 512) * 26 = 106 > NAND_OOBSIZE
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Thus BCH16 cannot be supported on 2K page NAND.
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However, for 4K pagesize NAND
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NAND_PAGESIZE = 4096
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NAND_OOBSIZE = 224
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ECC_BYTES = 26
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2 + (4096 / 512) * 26 = 210 < NAND_OOBSIZE
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Thus BCH16 can be supported on 4K page NAND.
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CONFIG_NAND_OMAP_GPMC_PREFETCH
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On OMAP platforms that use the GPMC controller
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(CONFIG_NAND_OMAP_GPMC_PREFETCH), this options enables the code that
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uses the prefetch mode to speed up read operations.
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NOTE:
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=====
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The Disk On Chip driver is currently broken and has been for some time.
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There is a driver in drivers/mtd/nand, taken from Linux, that works with
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the current NAND system but has not yet been adapted to the u-boot
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environment.
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Additional improvements to the NAND subsystem by Guido Classen, 10-10-2006
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JFFS2 related commands:
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implement "nand erase clean" and old "nand erase"
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using both the new code which is able to skip bad blocks
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"nand erase clean" additionally writes JFFS2-cleanmarkers in the oob.
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Miscellaneous and testing commands:
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"markbad [offset]"
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create an artificial bad block (for testing bad block handling)
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"scrub [offset length]"
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like "erase" but don't skip bad block. Instead erase them.
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DANGEROUS!!! Factory set bad blocks will be lost. Use only
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to remove artificial bad blocks created with the "markbad" command.
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"torture offset [size]"
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Torture block to determine if it is still reliable.
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Enabled by the CONFIG_CMD_NAND_TORTURE configuration option.
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This command returns 0 if the block is still reliable, else 1.
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If the block is detected as unreliable, it is up to the user to decide to
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mark this block as bad.
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The analyzed block is put through 3 erase / write cycles (or less if the block
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is detected as unreliable earlier).
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This command can be used in scripts, e.g. together with the markbad command to
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automate retries and handling of possibly newly detected bad blocks if the
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nand write command fails.
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It can also be used manually by users having seen some NAND errors in logs to
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search the root cause of these errors.
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The underlying nand_torture() function is also useful for code willing to
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automate actions following a nand->write() error. This would e.g. be required
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in order to program or update safely firmware to NAND, especially for the UBI
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part of such firmware.
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Optionally, a second parameter size can be given to test multiple blocks with
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one call. If size is not a multiple of the NAND's erase size, then the block
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that contains offset + size will be tested in full. If used with size, this
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command returns 0 if all tested blocks have been found reliable, else 1.
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NAND locking command (for chips with active LOCKPRE pin)
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"nand lock"
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set NAND chip to lock state (all pages locked)
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"nand lock tight"
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set NAND chip to lock tight state (software can't change locking anymore)
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"nand lock status"
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displays current locking status of all pages
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"nand unlock [offset] [size]"
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unlock consecutive area (can be called multiple times for different areas)
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"nand unlock.allexcept [offset] [size]"
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unlock all except specified consecutive area
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I have tested the code with board containing 128MiB NAND large page chips
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and 32MiB small page chips.
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