What is OTP in OneNAND?
The device includes,
1. one block-sized OTP (One Time Programmable) area and
2. user-controlled 1st block OTP(Block 0)
that can be used to increase system security or to provide
identification capabilities.
What is done?
In OneNAND, one block of the NAND Array is set aside as an OTP
memory area, and 1st Block (Block 0) can be used as OTP area.
This area, available to the user, can be configured and locked
with secured user information. The OTP block can be read,
programmed and locked using the same operations as any other NAND
Flash Array memory block. After issuing an OTP-Lock, OTP block
cannot be erased. OTP block is fully-guaranteed to be a good
block.
Why it is done?
Locking the 1st Block OTP has the effect of a 'Write-protect' to
guard against accidental re-programming of data stored in the 1st
block and OTP Block.
Which problem it solves?
OTP support is provided in the existing implementation of
OneNAND/Flex-OneNAND driver, but it is not working with OneNAND
devices. Have observed the following in current OTP OneNAND Implmentation,
1. DataSheet specific sequence to lock the OTP Area is not followed.
2. Certain functions are quiet generic to cope with OTP specific activity.
This patch re-implements OTP support for OneNAND device.
How it is done?
For all blocks, 8th word is available to the user.
However, in case of OTP Block, 8th word of sector 0, page 0 is reserved as
OTP Locking Bit area. Therefore, in case of OTP Block, user usage on this
area is prohibited. Condition specific values are entered in the 8th word,
sector0, page 0 of the OTP block during the process of issuing an OTP-Lock.
The possible conditions are:
1. Only 1st Block Lock
2. Only OTP Block Lock
3. Lock both the 1st Block and the OTP Block
What Other feature additions have been done in this patch?
This patch adds feature for:
1. Only 1st Block Lock
2. Lock both the 1st Block and the OTP Blocks
Re-implemented OTP support for OneNAND
Added following features to OneNAND
1. Lock only 1st Block in OneNAND
2. Lock BOTH 1st Block and OTP Block in OneNAND
[comments were slightly tweaked by Artem]
Signed-off-by: Amul Kumar Saha <amul.saha@samsung.com>
Reviewed-by: Adrian Hunter <adrian.hunter@nokia.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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