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 [off-list ref] wrote:

quoted

--- /dev/null
+++ b/drivers/irqchip/irq-jcore-aic.c

quoted

+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