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i.MX8MQ EVK: Failing to write SNVS registers from u-boot CLI

Question asked by Cyrill Gössi on Jul 27, 2020
Latest reply on Aug 11, 2020 by Cyrill Gössi

Hi all


I'm trying to access the SNVS registers from the interactive U-Boot CLI. Looking at the SNVS_HP Command Register (HPCOMR), I see field 31 as set and with this assume I should be able to access privileged registers:


u-boot=> md.l 0x30370004 1
30370004: 80002100


Then looking at the SNVS_LP Lock Register (LPLR), I see field 4 as not set and with this assume I should have write access to the monotonic counter and MC_ENV bit:


u-boot=> md.l 0x30370034 1
30370034: 00000000


Then looking at the SNVS_LP Control Register (LPCR) I see field 2 (MC_ENV) as not set and with this assume that the monotonic counter is disabled or invalid:


u-boot=> md.l 0x30370038 1
30370038: 00000020


Now I tried to enable the monotonic counter by setting this MC_ENV field of the LPCR register as follows:


u-boot=> mw.l 0x30370038 0x00000024


However, this has no effect:


u-boot=> md.l 0x30370038 1         
30370038: 00000020


What am I missing?


Many thanks,