[PATCH 1/5] ubi: introduce ubi->bad_peb_limit

[Shmulik Ladkani <shmulik.ladkani@gmail.com>]

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.

Signed-off-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
---
 arch/arm/configs/sam9_l9260_defconfig |    1 +
 drivers/mtd/ubi/Kconfig               |   11 +++++++++++
 drivers/mtd/ubi/build.c               |   13 ++++++++++++-
 drivers/mtd/ubi/ubi.h                 |    2 ++
 4 files changed, 26 insertions(+), 1 deletions(-)

diff --git a/arch/arm/configs/sam9_l9260_defconfig b/arch/arm/configs/sam9_l9260_defconfig
index ecf2531..f6917c9 100644
--- a/arch/arm/configs/sam9_l9260_defconfig
+++ b/arch/arm/configs/sam9_l9260_defconfig
@@ -40,6 +40,7 @@ CONFIG_MTD_NAND_ATMEL=y
 CONFIG_MTD_NAND_PLATFORM=y
 CONFIG_MTD_UBI=y
 CONFIG_MTD_UBI_BEB_RESERVE=3
+CONFIG_MTD_UBI_BEB_LIMIT=3
 CONFIG_MTD_UBI_GLUEBI=y
 CONFIG_BLK_DEV_LOOP=y
 CONFIG_BLK_DEV_RAM=y
diff --git a/drivers/mtd/ubi/Kconfig b/drivers/mtd/ubi/Kconfig
index 738ee8d..8df256f 100644
--- a/drivers/mtd/ubi/Kconfig
+++ b/drivers/mtd/ubi/Kconfig
@@ -42,6 +42,17 @@ config MTD_UBI_BEB_RESERVE
 	  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 eraseblocks UBI expects on the
+	  ubi device (percents of total number of flash eraseblocks).
+	  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)"
 	help
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 2c5ed5c..62cc6ce 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -607,8 +607,19 @@ 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 beb_limit;
+
+			beb_limit = mult_frac(ubi->peb_count, percent, 100);
+			/* round it up */
+			if (mult_frac(beb_limit, 100, percent) < ubi->peb_count)
+				beb_limit++;
+			ubi->bad_peb_limit = beb_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 a1a81c9..b5217ef 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;
-- 
1.7.9