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imx6sx M4 - enabling/hard reset from linux

Question asked by Jas Math on Jul 9, 2015
Latest reply on Jul 13, 2015 by Jas Math

I want to get clarification on the enabling/resetting the M4  because its not documented in the reference manual. From what I understand the following bits can cause the M4 to reset using the SCR (20D8000h) register


bit 3 - m4c_rst : M4 core reset

bit 4 - m4c_non_sclr_rst - Non-self-clearing SW reset for M4 core

bit 12 - m4p_rst : M4 platform reset


If the M4 isn't enabled from uboot via a bootaux, should it be possible to enable and reset the M4 (ie using bit 4 or bits 3+12) from a Linux application? From my testing with kernel 3.14:


1. enabling the M4 (bit 22) + resetting using bit 3+12 has no effect

2. enabling the M4 (bit 22) + resetting using bit 4 causes the kernel to hang.


As side note I would also like to point out the M4 is poorly documented as the reference manual no has description on what the M4 does when a reset occurs. From the code examples it seems to jump to address 0x007F8000 where it expects a Vector Table to exist?