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-rw-r--r--drivers/mtd/ubi/Kconfig40
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)"