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Diffstat (limited to 'README')
| -rw-r--r-- | README | 61 |
1 files changed, 61 insertions, 0 deletions
@@ -3338,6 +3338,9 @@ FIT uImage format: Adds the MTD partitioning infrastructure from the Linux kernel. Needed for UBI support. + CONFIG_MTD_NAND_VERIFY_WRITE + verify if the written data is correct reread. + - UBI support CONFIG_CMD_UBI @@ -3351,6 +3354,64 @@ FIT uImage format: Make the verbose messages from UBI stop printing. This leaves warnings and errors enabled. + + CONFIG_MTD_UBI_WL_THRESHOLD + 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). + + default: 4096 + + CONFIG_MTD_UBI_BEB_LIMIT + 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. + + default: 20 + + CONFIG_MTD_UBI_FASTMAP + 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 parameter + CONFIG_MTD_UBI_FASTMAP_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. + + CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT + Set this parameter to enable fastmap automatically on images + without a fastmap. + default: 0 + - UBIFS support CONFIG_CMD_UBIFS |