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- menu "UBI support"
- config MTD_UBI
- bool "Enable UBI - Unsorted block images"
- select CRC32
- help
- UBI is a software layer above MTD layer which admits of LVM-like
- logical volumes on top of MTD devices, hides some complexities of
- flash chips like wear and bad blocks and provides some other useful
- capabilities. Please, consult the MTD web site for more details
- (www.linux-mtd.infradead.org).
- if MTD_UBI
- config MTD_UBI_WL_THRESHOLD
- int "UBI wear-leveling threshold"
- default 4096
- range 2 65536
- help
- This parameter defines the maximum difference between the highest
- erase counter value and the lowest erase counter value of eraseblocks
- of UBI devices. When this threshold is exceeded, UBI starts performing
- wear leveling by means of moving data from eraseblock with low erase
- counter to eraseblocks with high erase counter.
- The default value should be OK for SLC NAND flashes, NOR flashes and
- other flashes which have eraseblock life-cycle 100000 or more.
- However, in case of MLC NAND flashes which typically have eraseblock
- life-cycle less than 10000, the threshold should be lessened (e.g.,
- to 128 or 256, although it does not have to be power of 2).
- config MTD_UBI_BEB_LIMIT
- int "Maximum expected bad eraseblock count per 1024 eraseblocks"
- default 20
- range 0 768
- help
- This option specifies the maximum bad physical eraseblocks UBI
- expects on the MTD device (per 1024 eraseblocks). If the underlying
- flash does not admit of bad eraseblocks (e.g. NOR flash), this value
- is ignored.
- NAND datasheets often specify the minimum and maximum NVM (Number of
- Valid Blocks) for the flashes' endurance lifetime. The maximum
- expected bad eraseblocks per 1024 eraseblocks then can be calculated
- as "1024 * (1 - MinNVB / MaxNVB)", which gives 20 for most NANDs
- (MaxNVB is basically the total count of eraseblocks on the chip).
- To put it differently, if this value is 20, UBI will try to reserve
- about 1.9% of physical eraseblocks for bad blocks handling. And that
- will be 1.9% of eraseblocks on the entire NAND chip, not just the MTD
- partition UBI attaches. This means that if you have, say, a NAND
- flash chip admits maximum 40 bad eraseblocks, and it is split on two
- MTD partitions of the same size, UBI will reserve 40 eraseblocks when
- attaching a partition.
- This option can be overridden by the "mtd=" UBI module parameter or
- by the "attach" ioctl.
- Leave the default value if unsure.
- config MTD_UBI_FASTMAP
- bool "UBI Fastmap (Experimental feature)"
- default n
- help
- Important: this feature is experimental so far and the on-flash
- format for fastmap may change in the next kernel versions
- Fastmap is a mechanism which allows attaching an UBI device
- in nearly constant time. Instead of scanning the whole MTD device it
- only has to locate a checkpoint (called fastmap) on the device.
- The on-flash fastmap contains all information needed to attach
- the device. Using fastmap makes only sense on large devices where
- attaching by scanning takes long. UBI will not automatically install
- a fastmap on old images, but you can set the UBI module parameter
- fm_autoconvert to 1 if you want so. Please note that fastmap-enabled
- images are still usable with UBI implementations without
- fastmap support. On typical flash devices the whole fastmap fits
- into one PEB. UBI will reserve PEBs to hold two fastmaps.
- If in doubt, say "N".
- config MTD_UBI_FASTMAP_AUTOCONVERT
- int "enable UBI Fastmap autoconvert"
- depends on MTD_UBI_FASTMAP
- default 0
- help
- Set this parameter to enable fastmap automatically on images
- without a fastmap.
- config MTD_UBI_FM_DEBUG
- int "Enable UBI fastmap debug"
- depends on MTD_UBI_FASTMAP
- default 0
- help
- Enable UBI fastmap debug
- endif # MTD_UBI
- endmenu # "Enable UBI - Unsorted block images"
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