Maximum expected bad eraseblock count per 1024 eraseblocks
configname: CONFIG_MTD_UBI_BEB_LIMIT
Linux Kernel Configuration
└─>Device Drivers
└─>Memory Technology Device (MTD) support
└─>Enable UBI - Unsorted block images
└─>Maximum expected bad eraseblock count per 1024 eraseblocks
In linux kernel since version 3.1 (release Date: 2011-10-24)
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.
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.