ARM Technical Support Knowledge Articles

How shold we connect Cortex-A5 to PL310 to assert PL310 idle when CPU is in standby ?

Applies to: Cortex-A5

Answer

If you have Cortex-A5 MPCore, then there is an SCUIDLE output which can be connected to PL310
STOPCLK.

If you are using Cortex-A5 UP, then you can connect STANDBYWFI to STOPCLK, or you can OR together
STANDBYWFI with STANDBYWFE and connect the OR result to STOPCLK.

Note that it is a mistake in the TRM where it says that STANBYWFI/E outputs are pulsed. They are
not – they are held high all the time the core is in standby.

If you are using PL310 rev3 with dynamic clock-gating enabled, then the clock will be gated after
32 cycles of inactivity, so it is not strictly necessary to use STOPCLK. In this case, there is
some delay while the clock is restarted. Use of STOPCLK avoids this clock restart delay.

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