arm64: Allow IPI_WAKEUP to be used outside of the ACPI parking protocol

An empty IPI is useful for cpuidle to wake sleeping CPUs without causing
them to do unnecessary work upon receipt of the IPI. IPI_WAKEUP fills
this use-case nicely, so let it be used outside of the ACPI parking
protocol.

Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com>
Signed-off-by: Adam W. Willis <return.of.octobot@gmail.com>

arch/arm64/include/asm/smp.h

@@ -95,14 +95,7 @@ extern void secondary_entry(void);
 extern void arch_send_call_function_single_ipi(int cpu);
 extern void arch_send_call_function_ipi_mask(const struct cpumask *mask);
 
-#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
 extern void arch_send_wakeup_ipi_mask(const struct cpumask *mask);
-#else
-static inline void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
-{
-	BUILD_BUG();
-}
-#endif
 
 extern int __cpu_disable(void);
 

arch/arm64/kernel/smp.c

@@ -794,12 +794,10 @@ void arch_send_call_function_single_ipi(int cpu)
 	smp_cross_call_common(cpumask_of(cpu), IPI_CALL_FUNC);
 }
 
-#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
 void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
 {
 	smp_cross_call_common(mask, IPI_WAKEUP);
 }
-#endif
 
 #ifdef CONFIG_IRQ_WORK
 void arch_irq_work_raise(void)
@@ -917,13 +915,8 @@ void handle_IPI(int ipinr, struct pt_regs *regs)
 		break;
 #endif
 
-#ifdef CONFIG_ARM64_ACPI_PARKING_PROTOCOL
 	case IPI_WAKEUP:
-		WARN_ONCE(!acpi_parking_protocol_valid(cpu),
-			  "CPU%u: Wake-up IPI outside the ACPI parking protocol\n",
-			  cpu);
 		break;
-#endif
 
 	default:
 		pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);