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Secondary SSBL partition on eMMC / trusted mode

Associate II

We would like to implement a dual partitioning system and I am trying to find out if it is possible to have a secondary SSBL (u-boot) partition in trusted mode (eMMC).

I don't see any problems for bootfs, vendorfs, rootfs and userfs. FSBL is already redundant, but I could not find anything about having a secondary SSBL partition. Is that possible? Also, if it is possible to have a secondary SSBL partition, how can I tell FSBL to use a determined SSBL partition? From what I could see in the TF-A code, that is not possible, just want a confirmation.

For context, all this is for updating a set of partitions when updating a device and switch to this set of partitions in the next boot.


Christophe Guibout
ST Employee

Hi @Community member​ ,

It is possible, but you will have to implement the mechanism to select the SSBL inside the FSBL.

I suppose you can use EXT_CSD from eMMC to select the FSBL, and the bootcount can be managed through a Backup registers (see TAMP_BKP21R).