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!
I don't think we can provide much help here - this is more likely a question for whoever created your board, and would require some knowledge of how you're obtaining this information.
However, it is legitimate for both PACCEPT and PDENY to equal 0. If the device is in either P_STABLE or P_REQUEST, then neither signal will be asserted. See Table 2-2 in the LPI Specification:
View all questions in Cortex-A / A-Profile forum