[U-Boot-Users] [PATCH, resend] Support dynamic/patched NAND ENV offset

[Harald Welte]

On Tue, Jul 08, 2008 at 11:12:31PM +0200, Wolfgang Denk wrote:
> In message <48739036.2080806 at freescale.com> you wrote:
> >
> > > I also have another patchset for what I call 'dynpart' support, i.e. the
> > > dynamic calculation of a unit-specific partition table that ensures the
> > > net size of partitions are as per spec, no matter how many of the
> > > factory default blocks are located where.  So it would even support
> > > NAND devices with a worse spec than the ones that we were using.
> > 
> > Interesting...  Would such a patch eliminate the need for this one, by 
> > making the environment a dynamic partition?  Is there any (plan for) 
> > Linux support?
> 
> What's the relation of this to the mtdparts handling in U-Boot and
> Linux?

see my other mail in this thread (just posted).  

More precisely, the flow of events in a full dynenv + dynpart setup
(like the three openmoko devices so far) is:

1) u-boot creates a bad block table as part of the production process
   of the device
2) afterwards, the device-unique partition table is created (net
   partition sizes as per board-level spec), including an environment
   partition.
3) the standard regular partition table is stored in the environment
4) the environment including the mtdparts variable is saved to the env
   partition
5) the nand flash offset to the environment partition is stored in the
   out-of-band area of the first (known-always-good) nand flash block

During boot, the regular mechanism of passing 'mtdparts' to the kernel
is used.

This was the most elegant scheme that I could come up with to support
a large number of factory-bad blocks at any given location in the flash
while still keeping the amount of overhead per partition low.

Cheers,
-- 
- Harald Welte <laforge at openmoko.org>          	        http://openmoko.org/
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