diff options
Diffstat (limited to 'drivers/mtd/ubi/Kconfig')
| -rw-r--r-- | drivers/mtd/ubi/Kconfig | 40 |
1 files changed, 27 insertions, 13 deletions
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig index ea4b95b5451c..271a842f8c39 100644 --- a/drivers/mtd/ubi/Kconfig +++ b/drivers/mtd/ubi/Kconfig @@ -27,20 +27,34 @@ config MTD_UBI_WL_THRESHOLD 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_RESERVE - int "Percentage of reserved eraseblocks for bad eraseblocks handling" - default 2 - range 0 25 +config MTD_UBI_BEB_LIMIT + int "Maximum expected bad eraseblock count per 1024 eraseblocks" + default 20 + range 0 768 help - If the MTD device admits of bad eraseblocks (e.g. NAND flash), UBI - reserves some amount of physical eraseblocks to handle new bad - eraseblocks. For example, if a flash physical eraseblock becomes bad, - UBI uses these reserved physical eraseblocks to relocate the bad one. - This option specifies how many physical eraseblocks will be reserved - for bad eraseblock handling (percents of total number of good flash - eraseblocks). If the underlying flash does not admit of bad - eraseblocks (e.g. NOR flash), this value is ignored and nothing is - reserved. Leave the default value if unsure. + 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_GLUEBI tristate "MTD devices emulation driver (gluebi)" |