diff options
| -rw-r--r-- | drivers/mtd/ubi/Kconfig | 27 | ||||
| -rw-r--r-- | drivers/mtd/ubi/build.c | 21 |
2 files changed, 39 insertions, 9 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 diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c index ce311aa75a75..9980441a8886 100644 --- a/drivers/mtd/ubi/build.c +++ b/drivers/mtd/ubi/build.c @@ -36,6 +36,7 @@ #include <linux/namei.h> #include <linux/stat.h> #include <linux/miscdevice.h> +#include <linux/mtd/partitions.h> #include <linux/log2.h> #include <linux/kthread.h> #include <linux/kernel.h> @@ -610,11 +611,25 @@ static int io_init(struct ubi_device *ubi) if (mtd_can_have_bb(ubi->mtd)) { ubi->bad_allowed = 1; if (CONFIG_MTD_UBI_BEB_LIMIT > 0) { - int percent = CONFIG_MTD_UBI_BEB_LIMIT; - int limit = mult_frac(ubi->peb_count, percent, 100); + int per1024 = CONFIG_MTD_UBI_BEB_LIMIT; + int limit, device_pebs; + uint64_t device_size; + + /* + * Here we are using size of the entire flash chip and + * not just the MTD partition size because the maximum + * number of bad eraseblocks is a percentage of the + * whole device and bad eraseblocks are not fairly + * distributed over the flash chip. So the worst case + * is that all the bad eraseblocks of the chip are in + * the MTD partition we are attaching (ubi->mtd). + */ + device_size = mtd_get_device_size(ubi->mtd); + device_pebs = mtd_div_by_eb(device_size, ubi->mtd); + limit = mult_frac(device_pebs, per1024, 1024); /* Round it up */ - if (mult_frac(limit, 100, percent) < ubi->peb_count) + if (mult_frac(limit, 1024, per1024) < device_pebs) limit += 1; ubi->bad_peb_limit = limit; } |
