UBI - exclude bootloader blocks from wear levelling

[Wolfgang Denk]

Dear "Darwin Rambo",

please do not top-post / full qoute. See
http://www.netmeister.org/news/learn2quote.html


In message <B125D8217ABC4B43826503DE00A2D44910DFC17927 at SJEXCHCCR01.corp.ad.broadcom.com> you wrote:
> I think Lauren must have been referring to a bootloader that lives
> outside the kernel and file system context. For example, a small,
> standalone bootloader downloaded from a serial port to it's own
> partition, would not be known to the kernel, as it is used to launch
> the kernel or later stage bootloaders. In this case it runs
> standalone and can't sit on UBI or be launched by a linux app. If

Of course it can, assuming it is UBI-aware by itself. For example,
U-Boot is such a boot loader that can load the U-Boot image itself
from a UBI partition in NAND.

> this small bootloader was only a block or two in size, and since it
> is typically burned once for production and then becomes read-only
> for each bootup after that, wear levelling is not required or
> possible.

Noite that "read-only" is not sufficient. NAND flash will develop
errors even if you just read it often enough. See for example this
Micron Application Note:
http://download.micron.com/pdf/technotes/nand/tn2917.pdf

> Flash data retention periods are usually specified in years, and

I am not talking about "data retention" here. See section "NAND Flash
is Not a Hard Drive" in the above Application Note to understand what
I mean.


Best regards,

Wolfgang Denk

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