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i.MX7: eMMC boot failure fallback to other boot partition?

Question asked by Jonah Petri on May 26, 2017
Latest reply on May 31, 2017 by Jonah Petri

Hello,

 

We are planning on using eMMC 5 for booting our i.MX7 custom board.  The software is field-upgradable, but must be able to fall back to the previous version if the upgrade is somehow nonfunctional.

 

What's the best way to implement this functionality?

  • I see there's PERSIST_SECONDARY_BOOT (IMX7DRM section 6.6.5.3.5), but this seems tricky to use, as it is persistent.  Is there a way to enable the secondary boot behavior *once*, and have it revert for the next boot?
  • MMC has boot0 and boot1 partitions, and the ROM seems to read the ext_csd registers to determine which to boot from (per "Figure 6-32. Expansion Device (MMC) Boot Flow (2 of 6)").  However, as above, this is a persistent setting in the eMMC, right? (I actually can't find confirmation of this anywhere.)

 

I'd love to hear some guidance as to the most fail-proof booting strategy for software upgrades.  Thanks!

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