[U-Boot] [PATCH] fw_env: add NAND support

[Guennadi Liakhovetski]

On Tue, 2 Sep 2008, Wolfgang Denk wrote:

> Note that this is a serious impairment compared to the  old  version.
> 
> The whole logic of writing the envrionment (and  especially  so  when
> redundancy  is  used)  is based on separate logic steps that are per-
> formed strictly sequentially, and only  when  the  previous  one  was
> successfully  completed.  This essential to maintain consistent data.
> For the redundant case that means:
> 
> 1) write the environment data to flash.
>    *After* this has completed, make the data valid by
> 2) writing the CRC checksum.
>    *After* this has completed, make this copy of the environment valid by
> 3) writing the valid flag to this copy.
>    *After* this has completed, make the other copy of the environment obsolete by
> 4) writing the obsolete flag to the other copy.

I am afraid, I cannot confirm this in the current version. In it first CRC 
and flag is written with one write, then the data, then optionally any 
residual data. Which seems like not providing any additional robustness. 
Would you like me to replicate this behaviour, in which case we could just 
as well write the whole buffer at once as I did up to now, or change it 
to follow your scheme above? In the latter case I am not sure if this will 
work with all kernel versions with all mtd drivers and all NOR flashes.

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
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