linux-phytec-fsl

MLK15034: ARM: cpuidle imx7d: Check IPIs manually before LPI

The GPC will wake us on peripheral interrupts but not IPIs. So check
them manually by reading the GIC's GICD_SPENDSGIR* registers and
aborting idle if something is pending.

We do this only for the last cpu and after taking the required locks.
We know that at this stage the other cpu is in WFI itself or waiting for
the imx_pen_lock and can't trigger any additional IPIs. This means that
the check is not racy.

This fixes occasional lost IPIs causing tasks to get stuck in the
TASK_WAKING 'W' state for long periods. This eventually manifested as
rcu stalls.

Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>