[PATCH v3 3/4] arm64: smp: Setup IPI_CALL_NMI_FUNC as a pseudo NMI

[Sumit Garg <sumit.garg@linaro.org>]

Setup IPI_CALL_NMI_FUNC as a pseudo NMI using generic interrupt framework
APIs. In case a plarform doesn't provide support for pseudo NMIs, switch
back to IPI_CALL_NMI_FUNC being a normal interrupt.

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
---
 arch/arm64/kernel/smp.c | 38 ++++++++++++++++++++++++++++----------
 1 file changed, 28 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 1b4c07c..572f8f5 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -81,6 +81,7 @@ enum ipi_msg_type {
 static int ipi_irq_base __read_mostly;
 static int nr_ipi __read_mostly = NR_IPI;
 static struct irq_desc *ipi_desc[NR_IPI] __read_mostly;
+static int ipi_nmi = -1;
 
 static void ipi_setup(int cpu);
 static void ipi_teardown(int cpu);
@@ -971,8 +972,14 @@ static void ipi_setup(int cpu)
 	if (WARN_ON_ONCE(!ipi_irq_base))
 		return;
 
-	for (i = 0; i < nr_ipi; i++)
-		enable_percpu_irq(ipi_irq_base + i, 0);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_nmi == ipi_irq_base + i) {
+			if (!prepare_percpu_nmi(ipi_nmi))
+				enable_percpu_nmi(ipi_nmi, 0);
+		} else {
+			enable_percpu_irq(ipi_irq_base + i, 0);
+		}
+	}
 }
 
 static void ipi_teardown(int cpu)
@@ -982,23 +989,34 @@ static void ipi_teardown(int cpu)
 	if (WARN_ON_ONCE(!ipi_irq_base))
 		return;
 
-	for (i = 0; i < nr_ipi; i++)
-		disable_percpu_irq(ipi_irq_base + i);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_nmi == ipi_irq_base + i) {
+			disable_percpu_nmi(ipi_nmi);
+			teardown_percpu_nmi(ipi_nmi);
+		} else {
+			disable_percpu_irq(ipi_irq_base + i);
+		}
+	}
 }
 
 void __init set_smp_ipi_range(int ipi_base, int n)
 {
-	int i;
+	int i, err;
 
 	WARN_ON(n < NR_IPI);
 	nr_ipi = min(n, NR_IPI);
 
-	for (i = 0; i < nr_ipi; i++) {
-		int err;
+	err = request_percpu_nmi(ipi_base + IPI_CALL_NMI_FUNC,
+				 ipi_handler, "IPI", &cpu_number);
+	if (!err)
+		ipi_nmi = ipi_base + IPI_CALL_NMI_FUNC;
 
-		err = request_percpu_irq(ipi_base + i, ipi_handler,
-					 "IPI", &cpu_number);
-		WARN_ON(err);
+	for (i = 0; i < nr_ipi; i++) {
+		if (ipi_base + i != ipi_nmi) {
+			err = request_percpu_irq(ipi_base + i, ipi_handler,
+						 "IPI", &cpu_number);
+			WARN_ON(err);
+		}
 
 		ipi_desc[i] = irq_to_desc(ipi_base + i);
 		irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
-- 
2.7.4