diff options
Diffstat (limited to 'drivers/mtd/ubi/Kconfig')
| -rw-r--r-- | drivers/mtd/ubi/Kconfig | 27 |
1 files changed, 21 insertions, 6 deletions
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig index b2f4f0f032f1..dcbaae3ead63 100644 --- a/drivers/mtd/ubi/Kconfig +++ b/drivers/mtd/ubi/Kconfig @@ -28,14 +28,29 @@ config MTD_UBI_WL_THRESHOLD to 128 or 256, although it does not have to be power of 2). config MTD_UBI_BEB_LIMIT - int "Percentage of maximum expected bad eraseblocks" - default 2 - range 0 25 + 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 UBI device (percents of total number of physical - eraseblocks on this MTD partition). If the underlying flash does not - admit of bad eraseblocks (e.g. NOR flash), this value is ignored. + 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. + Leave the default value if unsure. config MTD_UBI_GLUEBI |