ARC: smp: Introduce smp hook @init_irq_cpu called for all cores

Note this is not part of platform owned static machine_desc,
but more of device owned plat_smp_ops (rather misnamed) which a IPI
provider or some such typically defines.

This will help us seperate out the IPI registration from platform
specific init_cpu_smp() into device specific init_irq_cpu()
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/smp.h

@@ -48,6 +48,8 @@ extern int smp_ipi_irq_setup(int cpu, int irq);
  * @init_early_smp:	A SMP specific h/w block can init itself
  * 			Could be common across platforms so not covered by
  * 			mach_desc->init_early()
+ * @init_irq_cpu:	Called for each core so SMP h/w block driver can do
+ * 			any needed setup per cpu (e.g. IPI request)
  * @cpu_kick:		For Master to kickstart a cpu (optionally at a PC)
  * @ipi_send:		To send IPI to a @cpu
  * @ips_clear:		To clear IPI received at @irq
@@ -55,6 +57,7 @@ extern int smp_ipi_irq_setup(int cpu, int irq);
 struct plat_smp_ops {
 	const char 	*info;
 	void		(*init_early_smp)(void);
+	void		(*init_irq_cpu)(int cpu);
 	void		(*cpu_kick)(int cpu, unsigned long pc);
 	void		(*ipi_send)(int cpu);
 	void		(*ipi_clear)(int irq);

arch/arc/kernel/irq.c

@@ -10,6 +10,7 @@
 #include <linux/interrupt.h>
 #include <linux/irqchip.h>
 #include <asm/mach_desc.h>
+#include <asm/smp.h>
 
 /*
  * Late Interrupt system init called from start_kernel for Boot CPU only
@@ -27,7 +28,10 @@ void __init init_IRQ(void)
 	irqchip_init();
 
 #ifdef CONFIG_SMP
-	/* Master CPU can initialize it's side of IPI */
+	/* a SMP H/w block could do IPI IRQ request here */
+	if (plat_smp_ops.init_irq_cpu)
+		plat_smp_ops.init_irq_cpu(smp_processor_id());
+
 	if (machine_desc->init_cpu_smp)
 		machine_desc->init_cpu_smp(smp_processor_id());
 #endif

arch/arc/kernel/smp.c

@@ -131,6 +131,10 @@ void start_kernel_secondary(void)
 
 	pr_info("## CPU%u LIVE ##: Executing Code...\n", cpu);
 
+	/* Some SMP H/w setup - for each cpu */
+	if (plat_smp_ops.init_irq_cpu)
+		plat_smp_ops.init_irq_cpu(cpu);
+
 	if (machine_desc->init_cpu_smp)
 		machine_desc->init_cpu_smp(cpu);