System specification:
- i.MX 8QuadMax (IMX8QMRM) SoC
- DDR4 RAM: 4GB
- eMMC Flash: 16GB
- PMICs PF8200
- We are testing the Deep Sleep mode (Suspend2RAM), but when we're trying to resume the board with appropriate wakeup GPIO IRQ, the board reboots.
- Using light version of it (Susepnd2IDLE), everything works fine. With it, we are sure that our GPIO IRQ is working fine.
- While debugging, we've found out that in the period of resuming, dedicated System Control Unit (SCU) hangs around two seconds after triggering IRQ, and starts the reboot sequence.
- Measuring signals in that phase, using scope, we found out that SCU_WDOG_OUT signal goes to HIGH, and afterwards system reboots.
- SCU controls two PMICs, which SW outputs are power sources for A72 and A53 CPUs, that are a part of suspend-resume sequence. In suspend phase, SCU fw sets aforementioned outputs and some additional ones to LOW and it's expected to put them back to the HIGH in resume, but that's not happening. For that purpose, function "board_set_power_mode" is used, but in resume phase, it's never called.
- We’ve tried to find the trace for that function, and we’ve found that it should be:
Power_up_cpus -> prep_cpu-> pm_force_resource_power_mode-> pm_update_ridx-> ss_trans_power_mode-> sc_ss_ep[ss].ss_trans_power_mode -> ss_trans_power_mode_base->ss_trans_pd soc_trans_pd->board_set_power_mode->board_get_pmic_info-> pmic_init(board.c)
but it seems like that's not the case.
