What can cause getting Cortex-A55 DSU P-Channel PACCEPT/PDENY signals fail?

Hi experts,

I do an experiment about cpu power with a board which has 4 cores of Cortex-A55.

I try to power on/power off core1~3 parallelly.

Sometimes Both PACCEPT and PDENY are zero after changes the power state.

If I only power on/power off one core, the signals are normal, PACCEPT is asserted.

So I want to ask what can cause getting P-channel PACCEPT/PDENY fail.

Thanks for your attention!

Emmy

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