[Arm-netbook] Booting from SD card with switch on so-dimm in other direction ...

Luke Kenneth Casson Leighton luke.leighton at googlemail.com
Tue Mar 23 09:52:36 GMT 2010

On Tue, Mar 23, 2010 at 12:47 AM, Jonathan Ervine <jon.ervine at gmail.com> wrote:

> > make DAMN sure that's the right way round :)
> I have a 2GB SD card, so I can prep this with a view to trying to restore to
> Adam's system. We'll have to organise a convenient time to do this. I've got
> a busy weekend coming up when computing won't exactly be high priority ...
> Once the internal NAND is dd copied to the SD card is it expected that it
> should just 'boot', or would the three fingered salute be required?

think about it: if this works, then the SD card will have EXACTLY
what's on the NAND flash.  that means that it will try to reference
the NAND flash, because that's set up as mmcblk0p2, right?  and u-boot
is specifically hard-coded to set the bootparams to
root=/dev/mmcblk0p2, yes?

so... which partition will it boot off of?  the NAND flash, yes?

 which, in adam's case, has the remote possibility of having been
corrupted (but we don't know for sure).

 so, the sequence of events is _likely_ to be:

 * u-boot loads from SDcard
 * kernel loads from SDcard
 * kernel boots and uses root=/dev/mmblk0p2 which we expect to be NAND flash

 however if that switch _truly_ inverts /dev/mmcblk0 and /dev/mmcblk1
then of course /dev/mmcblk0p2 will be ... SDcard, yes?

 so a correct answer is: absolutely no idea, let us know what happens.

 the crucial and critical thing to get working is u-boot.  everything
can be recovered if u-boot can be booted.


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