ARC: [SMP] unify cpu private IRQ requests (TIMER/IPI)

The current cpu-private IRQ registration is ugly as it requires need to
expose arch_unmask_irq() outside of intc code.
So switch to percpu IRQ APIs:
  -request_percpu_irq [boot core]
  -enable_percpu_irq  [all cores]

Encapsulated in helper arc_request_percpu_irq()
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/irq.h

@@ -16,9 +16,13 @@
 #define TIMER0_IRQ      3
 #define TIMER1_IRQ      4
 
+#include <linux/interrupt.h>
 #include <asm-generic/irq.h>
 
 extern void arc_init_IRQ(void);
 void arc_local_timer_setup(void);
+void arc_request_percpu_irq(int irq, int cpu,
+                            irqreturn_t (*isr)(int irq, void *dev),
+                            const char *irq_nm, void *percpu_dev);
 
 #endif

arch/arc/kernel/irq.c

@@ -150,6 +150,32 @@ void arch_do_IRQ(unsigned int irq, struct pt_regs *regs)
 	set_irq_regs(old_regs);
 }
 
+void arc_request_percpu_irq(int irq, int cpu,
+                            irqreturn_t (*isr)(int irq, void *dev),
+                            const char *irq_nm,
+                            void *percpu_dev)
+{
+	/* Boot cpu calls request, all call enable */
+	if (!cpu) {
+		int rc;
+
+		/*
+		 * These 2 calls are essential to making percpu IRQ APIs work
+		 * Ideally these details could be hidden in irq chip map function
+		 * but the issue is IPIs IRQs being static (non-DT) and platform
+		 * specific, so we can't identify them there.
+		 */
+		irq_set_percpu_devid(irq);
+		irq_modify_status(irq, IRQ_NOAUTOEN, 0);  /* @irq, @clr, @set */
+
+		rc = request_percpu_irq(irq, isr, irq_nm, percpu_dev);
+		if (rc)
+			panic("Percpu IRQ request failed for %d\n", irq);
+	}
+
+	enable_percpu_irq(irq, 0);
+}
+
 /*
  * arch_local_irq_enable - Enable interrupts.
  *

arch/arc/kernel/smp.c

@@ -136,7 +136,7 @@ void start_kernel_secondary(void)
 	pr_info("## CPU%u LIVE ##: Executing Code...\n", cpu);
 
 	if (machine_desc->init_smp)
-		machine_desc->init_smp(smp_processor_id());
+		machine_desc->init_smp(cpu);
 
 	arc_local_timer_setup();
 
@@ -338,18 +338,11 @@ irqreturn_t do_IPI(int irq, void *dev_id)
  */
 static DEFINE_PER_CPU(int, ipi_dev);
 
-static struct irqaction arc_ipi_irq = {
-        .name    = "IPI Interrupt",
-        .flags   = IRQF_PERCPU,
-        .handler = do_IPI,
-};
-
 int smp_ipi_irq_setup(int cpu, int irq)
 {
-	if (!cpu)
-		return setup_irq(irq, &arc_ipi_irq);
-	else
-		arch_unmask_irq(irq);
+	int *dev = per_cpu_ptr(&ipi_dev, cpu);
+
+	arc_request_percpu_irq(irq, cpu, do_IPI, "IPI Interrupt", dev);
 
 	return 0;
 }

arch/arc/kernel/time.c

@@ -210,12 +210,6 @@ static irqreturn_t timer_irq_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static struct irqaction arc_timer_irq = {
-	.name    = "Timer0 (clock-evt-dev)",
-	.flags   = IRQF_TIMER | IRQF_PERCPU,
-	.handler = timer_irq_handler,
-};
-
 /*
  * Setup the local event timer for @cpu
  */
@@ -228,15 +222,9 @@ void arc_local_timer_setup()
 	clockevents_config_and_register(evt, arc_get_core_freq(),
 					0, ARC_TIMER_MAX);
 
-	/*
-	 * setup the per-cpu timer IRQ handler - for all cpus
-	 * For non boot CPU explicitly unmask at intc
-	 * setup_irq() -> .. -> irq_startup() already does this on boot-cpu
-	 */
-	if (!cpu)
-		setup_irq(TIMER0_IRQ, &arc_timer_irq);
-	else
-		arch_unmask_irq(TIMER0_IRQ);
+	/* setup the per-cpu timer IRQ handler - for all cpus */
+	arc_request_percpu_irq(TIMER0_IRQ, cpu, timer_irq_handler,
+			       "Timer0 (per-cpu-tick)", evt);
 }
 
 /*