UBI: introduce new bad PEB limit

Introduce 'ubi->bad_peb_limit', which specifies an upper limit of PEBs
UBI expects to go bad.  Currently, it is initialized to a fixed percentage
of total PEBs in the UBI device (configurable via CONFIG_MTD_UBI_BEB_LIMIT).

The 'bad_peb_limit' is intended to be used for calculating the amount of PEBs
UBI needs to reserve for bad eraseblock handling.

Artem: minor amendments.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@linux.intel.com>

3 files changed, 32 insertions, 8 deletions

diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index ea4b95b5451c..76195ac90e51 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -34,13 +34,25 @@ config MTD_UBI_BEB_RESERVE
         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.
+          eraseblocks. When a physical eraseblock becomes bad, UBI uses these
+          reserved physical eraseblocks to relocate the bad one. This
+          configuration option specifies how many physical eraseblocks will be
+          reserved for bad eraseblock handling (percents of total number of
+          good physical eraseblocks on this MTD partition). 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.
+
+config MTD_UBI_BEB_LIMIT
+        int "Percentage of maximum expected bad eraseblocks"
+        default 2
+        range 0 25
+        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.
+          Leave the default value if unsure.
 
 config MTD_UBI_GLUEBI
         tristate "MTD devices emulation driver (gluebi)"
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 3174dd40095d..ce311aa75a75 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -607,8 +607,18 @@ static int io_init(struct ubi_device *ubi)
         ubi->peb_count  = mtd_div_by_eb(ubi->mtd->size, ubi->mtd);
         ubi->flash_size = ubi->mtd->size;
 
-        if (mtd_can_have_bb(ubi->mtd))
+        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);
+
+                        /* Round it up */
+                        if (mult_frac(limit, 100, percent) < ubi->peb_count)
+                                limit += 1;
+                        ubi->bad_peb_limit = limit;
+                }
+        }
 
         if (ubi->mtd->type == MTD_NORFLASH) {
                 ubi_assert(ubi->mtd->writesize == 1);
diff --git a/drivers/mtd/ubi/ubi.h b/drivers/mtd/ubi/ubi.h
index 84f66e3fa05d..aeb459eb7e42 100644
--- a/drivers/mtd/ubi/ubi.h
+++ b/drivers/mtd/ubi/ubi.h
@@ -363,6 +363,7 @@ struct ubi_wl_entry;
  * @flash_size: underlying MTD device size (in bytes)
  * @peb_count: count of physical eraseblocks on the MTD device
  * @peb_size: physical eraseblock size
+ * @bad_peb_limit: top limit of expected bad physical eraseblocks
  * @bad_peb_count: count of bad physical eraseblocks
  * @good_peb_count: count of good physical eraseblocks
  * @corr_peb_count: count of corrupted physical eraseblocks (preserved and not
@@ -410,6 +411,7 @@ struct ubi_device {
         int avail_pebs;
         int beb_rsvd_pebs;
         int beb_rsvd_level;
+        int bad_peb_limit;
 
         int autoresize_vol_id;
         int vtbl_slots;