From: Felix Fietkau <nbd@nbd.name>
Date: Thu, 19 Jan 2017 12:14:44 +0100
Subject: [PATCH] MIPS: Lantiq: Fix cascaded IRQ setup

With the IRQ stack changes integrated, the XRX200 devices started
emitting a constant stream of kernel messages like this:

[  565.415310] Spurious IRQ: CAUSE=0x1100c300

This appears to be caused by IP0 firing for some reason without being
handled. Fix this by setting up IP2-6 as a proper chained IRQ handler and
calling do_IRQ for all MIPS CPU interrupts.

Cc: john@phrozen.org
Cc: stable@vger.kernel.org
Signed-off-by: Felix Fietkau <nbd@nbd.name>
---

--- a/arch/mips/lantiq/irq.c
+++ b/arch/mips/lantiq/irq.c
@@ -272,6 +272,11 @@ static void ltq_hw5_irqdispatch(void)
 DEFINE_HWx_IRQDISPATCH(5)
 #endif
 
+static void ltq_hw_irq_handler(struct irq_desc *desc)
+{
+	ltq_hw_irqdispatch(irq_desc_get_irq(desc) - 2);
+}
+
 #ifdef CONFIG_MIPS_MT_SMP
 void __init arch_init_ipiirq(int irq, struct irqaction *action)
 {
@@ -316,23 +321,19 @@ static struct irqaction irq_call = {
 asmlinkage void plat_irq_dispatch(void)
 {
 	unsigned int pending = read_c0_status() & read_c0_cause() & ST0_IM;
-	unsigned int i;
+	int irq;
 
-	if ((MIPS_CPU_TIMER_IRQ == 7) && (pending & CAUSEF_IP7)) {
-		do_IRQ(MIPS_CPU_TIMER_IRQ);
-		goto out;
-	} else {
-		for (i = 0; i < MAX_IM; i++) {
-			if (pending & (CAUSEF_IP2 << i)) {
-				ltq_hw_irqdispatch(i);
-				goto out;
-			}
-		}
+	if (!pending) {
+		spurious_interrupt();
+		return;
 	}
-	pr_alert("Spurious IRQ: CAUSE=0x%08x\n", read_c0_status());
 
-out:
-	return;
+	pending >>= CAUSEB_IP;
+	while (pending) {
+		irq = fls(pending) - 1;
+		do_IRQ(MIPS_CPU_IRQ_BASE + irq);
+		pending &= ~BIT(irq);
+	}
 }
 
 static int icu_map(struct irq_domain *d, unsigned int irq, irq_hw_number_t hw)
@@ -357,11 +358,6 @@ static const struct irq_domain_ops irq_d
 	.map = icu_map,
 };
 
-static struct irqaction cascade = {
-	.handler = no_action,
-	.name = "cascade",
-};
-
 int __init icu_of_init(struct device_node *node, struct device_node *parent)
 {
 	struct device_node *eiu_node;
@@ -393,7 +389,7 @@ int __init icu_of_init(struct device_nod
 	mips_cpu_irq_init();
 
 	for (i = 0; i < MAX_IM; i++)
-		setup_irq(i + 2, &cascade);
+		irq_set_chained_handler(i + 2, ltq_hw_irq_handler);
 
 	if (cpu_has_vint) {
 		pr_info("Setting up vectored interrupts\n");
