On Wed, Jul 27, 2016 at 11:12:36AM +0100, Mark Rutland wrote:

On Wed, Jul 27, 2016 at 05:35:09AM +0000, Rich Felker wrote:

quoted

+int __init aic_irq_of_init(struct device_node *node, struct device_node *parent)
+{
+	struct aic_data *aic = &aic_data;
+	unsigned min_irq = 64;
+
+	pr_info("Initializing J-Core AIC\n");
+
+	if (!of_device_is_compatible(node, "jcore,aic2")) {
+		unsigned cpu;
+		for_each_possible_cpu(cpu) {
+			void __iomem *base = of_iomap(node, cpu);
+			if (!base)
+				continue;

This sounds like it would be a critical error.

It would be best to at least pr_warn() if you can't map a CPU's AI
interface.

It's looping over possible cpus (per the kernel configuration for max
cpus) so it's expected that a system with fewer cpus will also have
fewer reg ranges for the aic. This is not an error. If you think
there's a different/better way I should write this code, I'm open to
suggestions.

quoted

+			pr_info("Local AIC1 enable for cpu %u at %p\n",
+				cpu, base + AIC1_INTPRI);
+			__raw_writel(0xffffffff, base + AIC1_INTPRI);
+		}

Here base goes out of scope. If you don't need it, it would be best
practice to iounmap it (even if that happens to be a no-op on your
arch).

OK. I can add that.

quoted

+		min_irq = 16;
+	}
+
+	aic->chip.name = node->name;

It's probably best to give the name explicitly in the driver (e.g.
"AIC"), rather than taknig whatever happens to be in the DT (which
should be 'interrupt-controller@<addr>'.

OK.

quoted

+	aic->chip.irq_mask = noop;
+	aic->chip.irq_unmask = noop;

If the core code wants to mask IRQs, how do you handle that? Can you
mask your CPU traps?

There's a global imask in the cpu that masks all interrupts that's
used in the trap entry point, spinlocks, etc. already. This is a cpu
standard feature and not logically part of the AIC. My understanding
is that the kernel already keeps a logical mask of disabled irqs in
addition to mask/disable at the irqchip level so there's a fairly fast
path for ignoring/holding (potentially spurious) irqs while they're
supposed to be disabled and deferring them until they're enabled
again.

Rich
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