This patch provides the possibility to adjust the "maximum expected number of
bad blocks per 1024 blocks" (max_beb_per1024) for each mtd device.

The majority of NAND devices have their max_beb_per1024 equal to 20, but
sometimes it's more.
Now, we can adjust that via a kernel parameter:
ubi.mtd=<name|num|path>[,<vid_hdr_offs>[,max_beb_per1024]]
Signed-off-by: NRichard Genoud <richard.genoud@gmail.com>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>

On NAND flash devices, UBI reserves some physical erase blocks (PEB) for
bad block handling. Today, the number of reserved PEB can only be set as a
percentage of the total number of PEB in each MTD partition. For example, for a
NAND flash with 128KiB PEB, 2 MTD partition of 20MiB (mtd0) and 100MiB (mtd1)
and 2% reserved PEB:
 - the UBI device on mtd0 will have 2 PEB reserved
 - the UBI device on mtd1 will have 16 PEB reserved

The problem with this behaviour is that NAND flash manufacturers give a
minimum number of valid block (NVB) during the endurance life of the
device, e.g.:

Parameter             Symbol    Min    Max    Unit      Notes
--------------------------------------------------------------
Valid block number     NVB     1004    1024   Blocks     1

From this number we can deduce the maximum number of bad PEB that a device will
contain during its endurance life: a 128MiB NAND flash (1024 PEB) will not have
less than 20 bad blocks during the flash endurance life.

But the manufacturer doesn't tell where those bad block will appear. He doesn't
say either if they will be equally disposed on the whole device (and I'm pretty
sure they won't). So, according to the datasheets, we should reserve the
maximum number of bad PEB for each UBI device (worst case scenario: 20 bad
blocks appears on the smallest MTD partition).

So this patch make UBI use the whole MTD device size to calculate the maximum
bad expected eraseblocks.

The Kconfig option is in per1024 blocks, thus it can have a default value of 20
which is *very* common for NAND devices.
Signed-off-by: NRichard Genoud <richard.genoud@gmail.com>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>

CONFIG_MTD_UBI_BEB_RESERVE and MIN_RESEVED_PEBS are no longer used,
since the amount of reserved eraseblocks for bad PEB handling is now
derived from 'ubi->bad_peb_limit' (ubi's maximum expected bad
eraseblocks).
Signed-off-by: NShmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@linux.intel.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.

Artem: minor amendments.
Signed-off-by: NShmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@linux.intel.com>

The actual value (1%) is too low for actual NAND devices, a huge
majority of device has 2% maximum bad blocks (SLC or MLC).
(Actually it's 20 blocks on a 1024 blocks device, 40/2048...)
Signed-off-by: NRichard Genoud <richard.genoud@gmail.com>

This patch kills the UBI debugging Kconfig option completely and makes all the
debugging stuff to be always compiled-in. It was pain in the neck to maintain
this useless option because all users I am aware of have debugging enabled
anyway - how else will you diagnose errors otherwise?
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>

All UBI needs is to make sure we stacktraces when UBI debugging
is enabled. It is enough to select KALLSYMS for this, KALLSYMS_ALL
is not necessary.

And the current Kconfig line we have:

select KALLSYMS_ALL if KALLSYMS && DEBUG_KERNEL

is just too complex to be sane and right. But this "if" part there
is needed to prevent "unmet direct dependency" warnings, because
KALLSYMS_ALL depends on KALLSYMS and DEBUG_KERNEL, so we cannot
just select KALLSYMS_ALL.

Anyway, this feels messy, and we do not seem to really need KALLSYMS_ALL,
so select KALLSYMS instead.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Acked-by: NRandy Dunlap <randy.dunlap@oracle.com>

Similarly to the debugging checks and message, make the test modes
be dynamically selected via the "debug_tsts" module parameter or
via the "/sys/module/ubi/parameters/debug_tsts" sysfs file. This
is consistent with UBIFS as well.

And now, since all the Kconfig knobs became dynamic, we can remove
the Kconfig.debug file completely.
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Cleanup the Kconfig for UBI by using menuconfig to enable/disable the entire
driver. Remove the dependency checks for MTD_UBI and MTD_UBI_DEBUG by
wrapping the options in if/endif blocks and remove any redundant checks.
Remove all default n since that is the Kconfig default. Change menu "Additional
UBI debugging messages" into a comment to remove one menu level.
Signed-off-by: NH Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NShinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Additionally, some excessive newlines removed.
Signed-off-by: NMichael Roth <mroth@nessie.de>
Signed-off-by: NJiri Kosina <jkosina@suse.cz>

[Artem: re-worked the patch: made it release resources when the
module is unloaded, made it do module referencing, made it really
independent on UBI, tested it with the UBI test-suite which can
be found in ubi-2.6.git/tests/ubi-tests, re-named most of the
funcs/variables to get rid of the "ubi" word and make names
consistent.]
Signed-off-by: NDmitry Pervushin <dpervushin@embeddedalley.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>

UBI (Latin: "where?") manages multiple logical volumes on a single
flash device, specifically supporting NAND flash devices. UBI provides
a flexible partitioning concept which still allows for wear-levelling
across the whole flash device.

In a sense, UBI may be compared to the Logical Volume Manager
(LVM). Whereas LVM maps logical sector numbers to physical HDD sector
numbers, UBI maps logical eraseblocks to physical eraseblocks.

More information may be found at
http://www.linux-mtd.infradead.org/doc/ubi.html

Partitioning/Re-partitioning

  An UBI volume occupies a certain number of erase blocks. This is
  limited by a configured maximum volume size, which could also be
  viewed as the partition size. Each individual UBI volume's size can
  be changed independently of the other UBI volumes, provided that the
  sum of all volume sizes doesn't exceed a certain limit.

  UBI supports dynamic volumes and static volumes. Static volumes are
  read-only and their contents are protected by CRC check sums.

Bad eraseblocks handling

  UBI transparently handles bad eraseblocks. When a physical
  eraseblock becomes bad, it is substituted by a good physical
  eraseblock, and the user does not even notice this.

Scrubbing

  On a NAND flash bit flips can occur on any write operation,
  sometimes also on read. If bit flips persist on the device, at first
  they can still be corrected by ECC, but once they accumulate,
  correction will become impossible. Thus it is best to actively scrub
  the affected eraseblock, by first copying it to a free eraseblock
  and then erasing the original. The UBI layer performs this type of
  scrubbing under the covers, transparently to the UBI volume users.

Erase Counts

  UBI maintains an erase count header per eraseblock. This frees
  higher-level layers (like file systems) from doing this and allows
  for centralized erase count management instead. The erase counts are
  used by the wear-levelling algorithm in the UBI layer. The algorithm
  itself is exchangeable.

Booting from NAND

  For booting directly from NAND flash the hardware must at least be
  capable of fetching and executing a small portion of the NAND
  flash. Some NAND flash controllers have this kind of support. They
  usually limit the window to a few kilobytes in erase block 0. This
  "initial program loader" (IPL) must then contain sufficient logic to
  load and execute the next boot phase.

  Due to bad eraseblocks, which may be randomly scattered over the
  flash device, it is problematic to store the "secondary program
  loader" (SPL) statically. Also, due to bit-flips it may become
  corrupted over time. UBI allows to solve this problem gracefully by
  storing the SPL in a small static UBI volume.

UBI volumes vs. static partitions

  UBI volumes are still very similar to static MTD partitions:

    * both consist of eraseblocks (logical eraseblocks in case of UBI
      volumes, and physical eraseblocks in case of static partitions;
    * both support three basic operations - read, write, erase.

  But UBI volumes have the following advantages over traditional
  static MTD partitions:

    * there are no eraseblock wear-leveling constraints in case of UBI
      volumes, so the user should not care about this;
    * there are no bit-flips and bad eraseblocks in case of UBI volumes.

  So, UBI volumes may be considered as flash devices with relaxed
  restrictions.

Where can it be found?

  Documentation, kernel code and applications can be found in the MTD
  gits.

What are the applications for?

  The applications help to create binary flash images for two purposes: pfi
  files (partial flash images) for in-system update of UBI volumes, and plain
  binary images, with or without OOB data in case of NAND, for a manufacturing
  step. Furthermore some tools are/and will be created that allow flash content
  analysis after a system has crashed..

Who did UBI?

  The original ideas, where UBI is based on, were developed by Andreas
  Arnez, Frank Haverkamp and Thomas Gleixner. Josh W. Boyer and some others
  were involved too. The implementation of the kernel layer was done by Artem
  B. Bityutskiy. The user-space applications and tools were written by Oliver
  Lohmann with contributions from Frank Haverkamp, Andreas Arnez, and Artem.
  Joern Engel contributed a patch which modifies JFFS2 so that it can be run on
  a UBI volume. Thomas Gleixner did modifications to the NAND layer. Alexander
  Schmidt made some testing work as well as core functionality improvements.
Signed-off-by: NArtem B. Bityutskiy <dedekind@linutronix.de>
Signed-off-by: NFrank Haverkamp <haver@vnet.ibm.com>