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Writing lpgpr via U-Boot

Question asked by Guy Shapiro on Aug 31, 2017
Latest reply on Sep 19, 2017 by igorpadykov

When I try to write the LPGPR of imx6ul via U-Boot, nothing happens:

=> md.l 020cc090 4
020cc090: 00000000 00000000 00000000 00000000    ................
=> mw.l 020cc090 12345678
=> md.l 020cc090 4      
020cc090: 00000000 00000000 00000000 00000000    ................

After the first time the Linux kernel is booted on on a system, the issue disappears:

=> mw.l 020cc090 12345678
=> md.l 020cc090 4
020cc090: 12345678 00000000 00000000 00000000    xV4.............

If the VDD_SNVS_IN power is removed, the issue returns on the next power on.

 

Probably some kind of initialization must happen on the snvs before the register can be written.

What am I doing wrong?

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