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This patch provides the possibility to adjust the "maximum expected number of bad blocks per 1024 blocks" (max_beb_per1024) for each mtd device. The majority of NAND devices have their max_beb_per1024 equal to 20, but sometimes it's more. Now, we can adjust that via a kernel parameter: ubi.mtd=<name|num|path>[,<vid_hdr_offs>[,max_beb_per1024]] Signed-off-by: Richard Genoud <richard.genoud@gmail.com> Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
69 lines
2.8 KiB
Plaintext
69 lines
2.8 KiB
Plaintext
menuconfig MTD_UBI
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tristate "Enable UBI - Unsorted block images"
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select CRC32
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help
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UBI is a software layer above MTD layer which admits of LVM-like
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logical volumes on top of MTD devices, hides some complexities of
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flash chips like wear and bad blocks and provides some other useful
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capabilities. Please, consult the MTD web site for more details
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(www.linux-mtd.infradead.org).
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if MTD_UBI
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config MTD_UBI_WL_THRESHOLD
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int "UBI wear-leveling threshold"
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default 4096
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range 2 65536
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help
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This parameter defines the maximum difference between the highest
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erase counter value and the lowest erase counter value of eraseblocks
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of UBI devices. When this threshold is exceeded, UBI starts performing
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wear leveling by means of moving data from eraseblock with low erase
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counter to eraseblocks with high erase counter.
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The default value should be OK for SLC NAND flashes, NOR flashes and
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other flashes which have eraseblock life-cycle 100000 or more.
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However, in case of MLC NAND flashes which typically have eraseblock
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life-cycle less than 10000, the threshold should be lessened (e.g.,
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to 128 or 256, although it does not have to be power of 2).
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config MTD_UBI_BEB_LIMIT
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int "Maximum expected bad eraseblock count per 1024 eraseblocks"
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default 20
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range 0 768
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help
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This option specifies the maximum bad physical eraseblocks UBI
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expects on the MTD device (per 1024 eraseblocks). If the underlying
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flash does not admit of bad eraseblocks (e.g. NOR flash), this value
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is ignored.
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NAND datasheets often specify the minimum and maximum NVM (Number of
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Valid Blocks) for the flashes' endurance lifetime. The maximum
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expected bad eraseblocks per 1024 eraseblocks then can be calculated
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as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
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(MaxNVB is basically the total count of eraseblocks on the chip).
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To put it differently, if this value is 20, UBI will try to reserve
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about 1.9% of physical eraseblocks for bad blocks handling. And that
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will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
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partition UBI attaches. This means that if you have, say, a NAND
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flash chip admits maximum 40 bad eraseblocks, and it is split on two
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MTD partitions of the same size, UBI will reserve 40 eraseblocks when
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attaching a partition.
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This option can be overridden by the "mtd=" UBI module parameter.
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Leave the default value if unsure.
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config MTD_UBI_GLUEBI
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tristate "MTD devices emulation driver (gluebi)"
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help
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This option enables gluebi - an additional driver which emulates MTD
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devices on top of UBI volumes: for each UBI volumes an MTD device is
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created, and all I/O to this MTD device is redirected to the UBI
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volume. This is handy to make MTD-oriented software (like JFFS2)
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work on top of UBI. Do not enable this unless you use legacy
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software.
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endif # MTD_UBI
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