Re: [PATCH v6 2/2] irqchip: add J-Core AIC driver

[Rich Felker]

On Thu, Aug 04, 2016 at 04:32:57PM +0200, Geert Uytterhoeven wrote:
> Hi Rich,
> 
> On Thu, Aug 4, 2016 at 6:30 AM, Rich Felker <dalias@xxxxxxxx> wrote:
> > --- /dev/null
> > +++ b/drivers/irqchip/irq-jcore-aic.c
> 
> > +int __init aic_irq_of_init(struct device_node *node, struct device_node *parent)
> > +{
> > +       unsigned min_irq = JCORE_AIC2_MIN_HWIRQ;
> > +       unsigned dom_sz = JCORE_AIC_MAX_HWIRQ+1;
> > +       struct irq_domain *domain;
> > +
> > +       pr_info("Initializing J-Core AIC\n");
> > +
> > +       /* AIC1 needs priority initialization to receive interrupts. */
> > +       if (of_device_is_compatible(node, "jcore,aic1")) {
> > +               unsigned cpu;
> > +
> > +               for_each_present_cpu(cpu) {
> > +                       void __iomem *base = of_iomap(node, cpu);
> 
> Just double checking, these regions are per-cpu hardware registers,
> and not related to other functionality at all?
> 
> I.e. when booting on an SMP-capable system a kernel compiled with
> CONFIG_SMP=n, or using the kernel command line option maxcpus=
> to reduce the number of CPUs, no ill effects happen by not mapping the
> region and not writing to the register below?

If you're not using a secondary cpu, there's no harm in ignoring its
aic completely.

Rich