in my project I use an i.MX6S and I have used code signing tool version 2.3.1 to sign u-boot.imx and boot.img of my Android 5.1 distribution.
Everything works fine and with my board fuse-locked I'm able to update only signed images.
Now I need to add signature also to Android Recovery image. I realized it similarly to boot.img signature and on board startup with correct keys combination I'm able to enter into a signed Recovery.
The problem is that if I made from Android UI a Factory Reset on reboot Recovery doesn't start and from this point also on startup doesn't start and I need to download again Recovery image with mfgtool to fix the problem.
It seems that factory reset corrupts in some way I don't understand the recovery partition.....any idea?