xref: /openbmc/u-boot/doc/README.nand (revision ae485b54)
1# SPDX-License-Identifier: GPL-2.0+
2NAND FLASH commands and notes
3
4See NOTE below!!!
5
6# (C) Copyright 2003
7# Dave Ellis, SIXNET, dge@sixnetio.com
8#
9
10Commands:
11
12   nand bad
13      Print a list of all of the bad blocks in the current device.
14
15   nand device
16      Print information about the current NAND device.
17
18   nand device num
19      Make device `num' the current device and print information about it.
20
21   nand erase off|partition size
22   nand erase clean [off|partition size]
23      Erase `size' bytes starting at offset `off'. Alternatively partition
24      name can be specified, in this case size will be eventually limited
25      to not exceed partition size (this behaviour applies also to read
26      and write commands). Only complete erase blocks can be erased.
27
28      If `erase' is specified without an offset or size, the entire flash
29      is erased. If `erase' is specified with partition but without an
30      size, the entire partition is erased.
31
32      If `clean' is specified, a JFFS2-style clean marker is written to
33      each block after it is erased.
34
35      This command will not erase blocks that are marked bad. There is
36      a debug option in cmd_nand.c to allow bad blocks to be erased.
37      Please read the warning there before using it, as blocks marked
38      bad by the manufacturer must _NEVER_ be erased.
39
40   nand info
41      Print information about all of the NAND devices found.
42
43   nand read addr ofs|partition size
44      Read `size' bytes from `ofs' in NAND flash to `addr'.  Blocks that
45      are marked bad are skipped.  If a page cannot be read because an
46      uncorrectable data error is found, the command stops with an error.
47
48   nand read.oob addr ofs|partition size
49      Read `size' bytes from the out-of-band data area corresponding to
50      `ofs' in NAND flash to `addr'. This is limited to the 16 bytes of
51      data for one 512-byte page or 2 256-byte pages. There is no check
52      for bad blocks or ECC errors.
53
54   nand write addr ofs|partition size
55      Write `size' bytes from `addr' to `ofs' in NAND flash.  Blocks that
56      are marked bad are skipped.  If a page cannot be read because an
57      uncorrectable data error is found, the command stops with an error.
58
59      As JFFS2 skips blocks similarly, this allows writing a JFFS2 image,
60      as long as the image is short enough to fit even after skipping the
61      bad blocks.  Compact images, such as those produced by mkfs.jffs2
62      should work well, but loading an image copied from another flash is
63      going to be trouble if there are any bad blocks.
64
65   nand write.trimffs addr ofs|partition size
66      Enabled by the CONFIG_CMD_NAND_TRIMFFS macro. This command will write to
67      the NAND flash in a manner identical to the 'nand write' command
68      described above -- with the additional check that all pages at the end
69      of eraseblocks which contain only 0xff data will not be written to the
70      NAND flash. This behaviour is required when flashing UBI images
71      containing UBIFS volumes as per the UBI FAQ[1].
72
73      [1] http://www.linux-mtd.infradead.org/doc/ubi.html#L_flasher_algo
74
75   nand write.oob addr ofs|partition size
76      Write `size' bytes from `addr' to the out-of-band data area
77      corresponding to `ofs' in NAND flash. This is limited to the 16 bytes
78      of data for one 512-byte page or 2 256-byte pages. There is no check
79      for bad blocks.
80
81   nand read.raw addr ofs|partition [count]
82   nand write.raw addr ofs|partition [count]
83      Read or write one or more pages at "ofs" in NAND flash, from or to
84      "addr" in memory.  This is a raw access, so ECC is avoided and the
85      OOB area is transferred as well.  If count is absent, it is assumed
86      to be one page.  As with .yaffs2 accesses, the data is formatted as
87      a packed sequence of "data, oob, data, oob, ..." -- no alignment of
88      individual pages is maintained.
89
90Configuration Options:
91
92   CONFIG_SYS_NAND_U_BOOT_OFFS
93	NAND Offset from where SPL will read u-boot image. This is the starting
94	address of u-boot MTD partition in NAND.
95
96   CONFIG_CMD_NAND
97      Enables NAND support and commands.
98
99   CONFIG_CMD_NAND_TORTURE
100      Enables the torture command (see description of this command below).
101
102   CONFIG_SYS_MAX_NAND_DEVICE
103      The maximum number of NAND devices you want to support.
104
105   CONFIG_SYS_NAND_MAX_ECCPOS
106      If specified, overrides the maximum number of ECC bytes
107      supported.  Useful for reducing image size, especially with SPL.
108      This must be at least 48 if nand_base.c is used.
109
110   CONFIG_SYS_NAND_MAX_OOBFREE
111      If specified, overrides the maximum number of free OOB regions
112      supported.  Useful for reducing image size, especially with SPL.
113      This must be at least 2 if nand_base.c is used.
114
115   CONFIG_SYS_NAND_MAX_CHIPS
116      The maximum number of NAND chips per device to be supported.
117
118   CONFIG_SYS_NAND_SELF_INIT
119      Traditionally, glue code in drivers/mtd/nand/nand.c has driven
120      the initialization process -- it provides the mtd and nand
121      structs, calls a board init function for a specific device,
122      calls nand_scan(), and registers with mtd.
123
124      This arrangement does not provide drivers with the flexibility to
125      run code between nand_scan_ident() and nand_scan_tail(), or other
126      deviations from the "normal" flow.
127
128      If a board defines CONFIG_SYS_NAND_SELF_INIT, drivers/mtd/nand/nand.c
129      will make one call to board_nand_init(), with no arguments.  That
130      function is responsible for calling a driver init function for
131      each NAND device on the board, that performs all initialization
132      tasks except setting mtd->name, and registering with the rest of
133      U-Boot.  Those last tasks are accomplished by calling  nand_register()
134      on the new mtd device.
135
136      Example of new init to be added to the end of an existing driver
137      init:
138
139	/* chip is struct nand_chip, and is now provided by the driver. */
140	mtd = nand_to_mtd(&chip);
141
142	/*
143	 * Fill in appropriate values if this driver uses these fields,
144	 * or uses the standard read_byte/write_buf/etc. functions from
145	 * nand_base.c that use these fields.
146	 */
147	chip.IO_ADDR_R = ...;
148	chip.IO_ADDR_W = ...;
149
150	if (nand_scan_ident(mtd, CONFIG_SYS_MAX_NAND_CHIPS, NULL))
151		error out
152
153	/*
154	 * Insert here any code you wish to run after the chip has been
155	 * identified, but before any other I/O is done.
156	 */
157
158	if (nand_scan_tail(mtd))
159		error out
160
161	/*
162	 * devnum is the device number to be used in nand commands
163	 * and in mtd->name.  Must be less than CONFIG_SYS_MAX_NAND_DEVICE.
164	 */
165	if (nand_register(devnum, mtd))
166		error out
167
168      In addition to providing more flexibility to the driver, it reduces
169      the difference between a U-Boot driver and its Linux counterpart.
170      nand_init() is now reduced to calling board_nand_init() once, and
171      printing a size summary.  This should also make it easier to
172      transition to delayed NAND initialization.
173
174      Please convert your driver even if you don't need the extra
175      flexibility, so that one day we can eliminate the old mechanism.
176
177
178   CONFIG_SYS_NAND_ONFI_DETECTION
179	Enables detection of ONFI compliant devices during probe.
180	And fetching device parameters flashed on device, by parsing
181	ONFI parameter page.
182
183Platform specific options
184=========================
185   CONFIG_NAND_OMAP_GPMC
186	Enables omap_gpmc.c driver for OMAPx and AMxxxx platforms.
187	GPMC controller is used for parallel NAND flash devices, and can
188	do ECC calculation (not ECC error detection) for HAM1, BCH4, BCH8
189	and BCH16 ECC algorithms.
190
191   CONFIG_NAND_OMAP_ELM
192	Enables omap_elm.c driver for OMAPx and AMxxxx platforms.
193	ELM controller is used for ECC error detection (not ECC calculation)
194	of BCH4, BCH8 and BCH16 ECC algorithms.
195	Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
196	thus such SoC platforms need to depend on software library for ECC error
197	detection. However ECC calculation on such plaforms would still be
198	done by GPMC controller.
199
200   CONFIG_SPL_NAND_AM33XX_BCH
201	Enables SPL-NAND driver (am335x_spl_bch.c) which supports ELM based
202        hardware ECC correction. This is useful for platforms which have ELM
203	hardware engine and use NAND boot mode.
204	Some legacy platforms like OMAP3xx do not have in-built ELM h/w engine,
205	so those platforms should use CONFIG_SPL_NAND_SIMPLE for enabling
206        SPL-NAND driver with software ECC correction support.
207
208   CONFIG_NAND_OMAP_ECCSCHEME
209	On OMAP platforms, this CONFIG specifies NAND ECC scheme.
210	It can take following values:
211	OMAP_ECC_HAM1_CODE_SW
212		1-bit Hamming code using software lib.
213		(for legacy devices only)
214	OMAP_ECC_HAM1_CODE_HW
215		1-bit Hamming code using GPMC hardware.
216		(for legacy devices only)
217	OMAP_ECC_BCH4_CODE_HW_DETECTION_SW
218		4-bit BCH code (unsupported)
219	OMAP_ECC_BCH4_CODE_HW
220		4-bit BCH code (unsupported)
221	OMAP_ECC_BCH8_CODE_HW_DETECTION_SW
222		8-bit BCH code with
223		- ecc calculation using GPMC hardware engine,
224		- error detection using software library.
225		- requires CONFIG_BCH to enable software BCH library
226		(For legacy device which do not have ELM h/w engine)
227	OMAP_ECC_BCH8_CODE_HW
228		8-bit BCH code with
229		- ecc calculation using GPMC hardware engine,
230		- error detection using ELM hardware engine.
231	OMAP_ECC_BCH16_CODE_HW
232		16-bit BCH code with
233		- ecc calculation using GPMC hardware engine,
234		- error detection using ELM hardware engine.
235
236	How to select ECC scheme on OMAP and AMxx platforms ?
237	-----------------------------------------------------
238	Though higher ECC schemes have more capability to detect and correct
239	bit-flips, but still selection of ECC scheme is dependent on following
240	- hardware engines present in SoC.
241		Some legacy OMAP SoC do not have ELM h/w engine thus such
242		SoC cannot support BCHx_HW ECC schemes.
243	- size of OOB/Spare region
244		With higher ECC schemes, more OOB/Spare area is required to
245		store ECC. So choice of ECC scheme is limited by NAND oobsize.
246
247	In general following expression can help:
248		NAND_OOBSIZE >= 2 + (NAND_PAGESIZE / 512) * ECC_BYTES
249	where
250		NAND_OOBSIZE	= number of bytes available in
251				OOB/spare area per NAND page.
252		NAND_PAGESIZE	= bytes in main-area of NAND page.
253		ECC_BYTES	= number of ECC bytes generated to
254				protect 512 bytes of data, which is:
255				3 for HAM1_xx ecc schemes
256				7 for BCH4_xx ecc schemes
257				14 for BCH8_xx ecc schemes
258				26 for BCH16_xx ecc schemes
259
260		example to check for BCH16 on 2K page NAND
261		NAND_PAGESIZE = 2048
262		NAND_OOBSIZE = 64
263		2 + (2048 / 512) * 26 = 106 > NAND_OOBSIZE
264		Thus BCH16 cannot be supported on 2K page NAND.
265
266		However, for 4K pagesize NAND
267		NAND_PAGESIZE = 4096
268		NAND_OOBSIZE = 224
269		ECC_BYTES = 26
270		2 + (4096 / 512) * 26 = 210 < NAND_OOBSIZE
271		Thus BCH16 can be supported on 4K page NAND.
272
273
274    CONFIG_NAND_OMAP_GPMC_PREFETCH
275	On OMAP platforms that use the GPMC controller
276	(CONFIG_NAND_OMAP_GPMC_PREFETCH), this options enables the code that
277	uses the prefetch mode to speed up read operations.
278
279NOTE:
280=====
281
282The Disk On Chip driver is currently broken and has been for some time.
283There is a driver in drivers/mtd/nand, taken from Linux, that works with
284the current NAND system but has not yet been adapted to the u-boot
285environment.
286
287Additional improvements to the NAND subsystem by Guido Classen, 10-10-2006
288
289JFFS2 related commands:
290
291  implement "nand erase clean" and old "nand erase"
292  using both the new code which is able to skip bad blocks
293  "nand erase clean" additionally writes JFFS2-cleanmarkers in the oob.
294
295Miscellaneous and testing commands:
296  "markbad [offset]"
297  create an artificial bad block (for testing bad block handling)
298
299  "scrub [offset length]"
300  like "erase" but don't skip bad block. Instead erase them.
301  DANGEROUS!!! Factory set bad blocks will be lost. Use only
302  to remove artificial bad blocks created with the "markbad" command.
303
304  "torture offset [size]"
305  Torture block to determine if it is still reliable.
306  Enabled by the CONFIG_CMD_NAND_TORTURE configuration option.
307  This command returns 0 if the block is still reliable, else 1.
308  If the block is detected as unreliable, it is up to the user to decide to
309  mark this block as bad.
310  The analyzed block is put through 3 erase / write cycles (or less if the block
311  is detected as unreliable earlier).
312  This command can be used in scripts, e.g. together with the markbad command to
313  automate retries and handling of possibly newly detected bad blocks if the
314  nand write command fails.
315  It can also be used manually by users having seen some NAND errors in logs to
316  search the root cause of these errors.
317  The underlying nand_torture() function is also useful for code willing to
318  automate actions following a nand->write() error. This would e.g. be required
319  in order to program or update safely firmware to NAND, especially for the UBI
320  part of such firmware.
321  Optionally, a second parameter size can be given to test multiple blocks with
322  one call. If size is not a multiple of the NAND's erase size, then the block
323  that contains offset + size will be tested in full. If used with size, this
324  command returns 0 if all tested blocks have been found reliable, else 1.
325
326
327NAND locking command (for chips with active LOCKPRE pin)
328
329  "nand lock"
330  set NAND chip to lock state (all pages locked)
331
332  "nand lock tight"
333  set NAND chip to lock tight state (software can't change locking anymore)
334
335  "nand lock status"
336  displays current locking status of all pages
337
338  "nand unlock [offset] [size]"
339  unlock consecutive area (can be called multiple times for different areas)
340
341  "nand unlock.allexcept [offset] [size]"
342  unlock all except specified consecutive area
343
344I have tested the code with board containing 128MiB NAND large page chips
345and 32MiB small page chips.
346