config GAMECUBE_COMMON
 	bool
 	select NOT_COHERENT_CACHE
+	select FLIPPER_PIC

Maybe using FLIPPER (or GAMECUBE_FLIPPER) instead of GAMECUBE_COMMON
is a good name?

+#define pr_fmt(fmt) DRV_MODULE_NAME ": " fmt

Unused

+/*
+ * Each interrupt has a corresponding bit in both
+ * the Interrupt Cause (ICR) and Interrupt Mask (IMR) registers.
+ *
+ * Enabling/disabling an interrupt line involves asserting/clearing
+ * the corresponding bit in IMR. ACK'ing a request simply involves
+ * asserting the corresponding bit in ICR.
+ */

+static void flipper_pic_ack(unsigned int virq)
+{
+	int irq = virq_to_hw(virq);
+	void __iomem *io_base = get_irq_chip_data(virq);
+
+	set_bit(irq, io_base + FLIPPER_ICR);
+}

So it should be a simple write instead of an RMW here, right?
As it is you are ACKing _all_ IRQs as far as I can see.

+unsigned int flipper_pic_get_irq(void)
+{
+	void __iomem *io_base = flipper_irq_host->host_data;
+	int irq;
+	u32 irq_status;
+
+	irq_status = in_be32(io_base + FLIPPER_ICR) &
+		     in_be32(io_base + FLIPPER_IMR);
+	if (irq_status == 0)
+		return -1;	/* no more IRQs pending */
+
+	__asm__ __volatile__("cntlzw %0,%1" : "=r"(irq) : "r"(irq_status));
+	return irq_linear_revmap(flipper_irq_host, 31 - irq);
+}

There are generic macros for this kind of thing, no need for asm.  ffs()
or something.


Segher