ARC: SMP resurrect foss-for-synopsys-dwc-arc-processors#22: [plat-arc…

…fpga] IPI fixes

1. IPI was not going from cpu1 -> cpu0. Turns out that the IRQ mode
   programmed IDU_IRQ_MOD_TCPU_ALLRECP mismatched in value in kernel and
   ISS. kernel (per IDU specs) defines it as '3' whereas ISS believes it
   shd be 7 (which is clearly a BUG).

2. the IDU IRQs are hardwaired hence need to be setup as IRQF_PERCPU to
    disallow any irq-affinity changes.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/kernel/smp.c

@@ -321,7 +321,7 @@ irqreturn_t do_IPI(int irq, void *dev_id)
  */
 int smp_ipi_irq_setup(int cpu, int irq)
 {
-	return request_irq(irq, do_IPI, 0, "IPI Interrupt", NULL);
+	return request_irq(irq, do_IPI, IRQF_PERCPU, "IPI Interrupt", NULL);
 }
 
 struct cpu cpu_topology[NR_CPUS];

arch/arc/plat-arcfpga/smp.c

@@ -66,7 +66,7 @@ void arc_platform_smp_init_cpu(void)
 
 	/* Check if CPU is configured for more than 16 interrupts */
 	if (NR_IRQS <= 16 || get_hw_config_num_irq() <= 16)
-		BUG();
+		panic("[arcfpga] IRQ system can't support IDU IPI\n");
 
 	/* Setup the interrupt in IDU */
 	idu_disable();
@@ -75,8 +75,8 @@ void arc_platform_smp_init_cpu(void)
 			   (0x1 << cpu)	/* target cpus mask, here single cpu */
 	    );
 
-	idu_irq_set_mode(cpu,	/* IDU IRQ assoc with CPU */
-			 IDU_IRQ_MOD_TCPU_ALLRECP, IDU_IRQ_MODE_PULSE_TRIG);
+	idu_irq_set_mode(cpu, 7, /* XXX: IDU_IRQ_MOD_TCPU_ALLRECP: ISS bug */
+                         IDU_IRQ_MODE_PULSE_TRIG);
 
 	idu_enable();