[FS#821] sysupgrade doesn't work on Linksys WRT3200ACM (mvebu)

[LEDE Bugs]

The following task has a new comment added:

FS#821 - sysupgrade doesn't work on Linksys WRT3200ACM (mvebu)
User who did this - Hannu Nyman (hnyman)

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I tested sysupgrading wrt3200acm from r4283 to r4291 and failed with similar symptoms as diizzyy. After a manual power-off the router rebooted to the old firmware, so no actual flashing had been done.
 
But I sysupgraded ok from r4289 to r4291 with ipq806x R7800 that is also a NAND device, so sysupgrade still works for some targets.

So, the bug may be related to just mvebu, not the general NAND sysupgrade.

I noticed that the large sysupgrade patch set two days ago made target-specific changes to e.g. x86, sunxi and ramips, but did not touch mvebu. Maybe some target-specific change needs to be done also for mvebu.

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More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=821#comment2713