irq: nds32: avoid CONFIG_HANDLE_DOMAIN_IRQ

In preparation for removing HANDLE_DOMAIN_IRQ, have arch/nds32 perform
all the necessary IRQ entry accounting in its entry code.

Currently arch/nds32 is tightly coupled with the ativic32 irqchip, and
while the entry code should logically live under arch/nds32/, moving the
entry logic there makes things more convoluted. So for now, place the
entry logic in the ativic32 irqchip, but separated into a separate
function to make the split of responsibility clear.

In future this should probably use GENERIC_IRQ_MULTI_HANDLER to cleanly
decouple this.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <[e-mail]>
Reviewed-by: Marc Zyngier <[e-mail]>
Cc: Greentime Hu <[e-mail]>
Cc: Nick Hu <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Vincent Chen <[e-mail]>

arch/nds32/Kconfig

···
 	select GENERIC_LIB_MULDI3
 	select GENERIC_LIB_UCMPDI2
 	select GENERIC_TIME_VSYSCALL
-	select HANDLE_DOMAIN_IRQ
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_EXIT_THREAD

drivers/irqchip/irq-ativic32.c

···
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_address.h>
+#include <linux/hardirq.h>
 #include <linux/interrupt.h>
 #include <linux/irqdomain.h>
 #include <linux/irqchip.h>
 #include <nds32_intrinsic.h>
+
+#include <asm/irq_regs.h>
 
 unsigned long wake_mask;
 
···
 		- NDS32_VECTOR_offINTERRUPT;
 }
 
-asmlinkage void asm_do_IRQ(struct pt_regs *regs)
+static void ativic32_handle_irq(struct pt_regs *regs)
 {
 	irq_hw_number_t hwirq = get_intr_src();
-	handle_domain_irq(root_domain, hwirq, regs);
+	generic_handle_domain_irq(root_domain, hwirq);
+}
+
+/*
+ * TODO: convert nds32 to GENERIC_IRQ_MULTI_HANDLER so that this entry logic
+ * can live in arch code.
+ */
+asmlinkage void asm_do_IRQ(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs;
+
+	irq_enter();
+	old_regs = set_irq_regs(regs);
+	ativic32_handle_irq(regs);
+	set_irq_regs(old_regs);
+	irq_exit();
 }
 
 int __init ativic32_init_irq(struct device_node *node, struct device_node *parent)