[U-Boot-Users] u-boot locking ?

Wolfgang Denk wd at denx.de
Sun Jan 8 18:45:52 CET 2006

In message <29f916510601080721vd20b512u819ee9bce7ad1408 at mail.gmail.com> you wrote:
> 1) Does u-boot lock the block on which it resides by default ?

Not by default, but you can inplement in your flah  driver  whichever
features you like.

> I mean the sector /erase block on which u-boot is there, it will be
> locked using the block lock  bit by default ?

Remember that only few flash chips provide such hardware locking, and
that some boards implement even other ways  of  write  protection  of
parts of or of the whole flash device.

> 2) The flash content changing has to work in block sizes erase -
> modify - write cyecles only ??

No. You can write single bytes (as long as you are only changing  '1'
bits to '0').

> Reason for all this is that we have few boards on which u-boot is
> getting corrupted (on flash image corruption itself).
> And so am wondering even if its a noise issue, how can it first cause
> an unlock of sector before write.

Normally the flash is  not  hardare  write  protected,  and  if  your
hardware designer used flash chips which can be corrupted for example
by  just writing arbitrary data to a sequential address range you may
easily see such corruption. There is a very good reason why AMD flash
chips require a specific programming sequence which must  be  written
in a certain sequence to certain non-consequitive addresses. 

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
PoB = "Prisoner of Bill" -- those held captive, unwillingly or other-
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         -- Tom Christiansen in <6abo45$3lc$2 at csnews.cs.colorado.edu>

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