MPIC_IN_DRBEL_CAUSE
writel(~BIT(d->hwirq), mpic->per_cpu + MPIC_IN_DRBEL_CAUSE);
writel(0, mpic->per_cpu + MPIC_IN_DRBEL_CAUSE);
cause = readl_relaxed(mpic->per_cpu + MPIC_IN_DRBEL_CAUSE);
writel(~cause, mpic->per_cpu + MPIC_IN_DRBEL_CAUSE);
cause = readl_relaxed(mpic->per_cpu + MPIC_IN_DRBEL_CAUSE);