genirq: Introduce a new flag IRQ_IS_CHAINED for chained interrupts

index 6bcfe8ac7594..cefdb36eb3e9 100644
@@ -72,6 +72,7 @@ enum irqchip_irq_state;
  * IRQ_IS_POLLED		- Always polled by another interrupt. Exclude
  *				  it from the spurious interrupt detection
  *				  mechanism and from core side polling.
+ * IRQ_IS_CHAINED		- Interrupt has chained handler installed
  */
 enum {
 	IRQ_TYPE_NONE		= 0x00000000,

@@ -97,13 +98,14 @@ enum {
 	IRQ_NOTHREAD		= (1 << 16),
 	IRQ_PER_CPU_DEVID	= (1 << 17),
 	IRQ_IS_POLLED		= (1 << 18),
+	IRQ_IS_CHAINED		= (1 << 19),
 };
 
 #define IRQF_MODIFY_MASK	\
 	(IRQ_TYPE_SENSE_MASK | IRQ_NOPROBE | IRQ_NOREQUEST | \
 	 IRQ_NOAUTOEN | IRQ_MOVE_PCNTXT | IRQ_LEVEL | IRQ_NO_BALANCING | \
 	 IRQ_PER_CPU | IRQ_NESTED_THREAD | IRQ_NOTHREAD | IRQ_PER_CPU_DEVID | \
-	 IRQ_IS_POLLED)
+	 IRQ_IS_POLLED | IRQ_IS_CHAINED)
 
 #define IRQ_NO_BALANCING_MASK	(IRQ_PER_CPU | IRQ_NO_BALANCING)
 

@@ -544,6 +546,8 @@ void
 irq_set_chained_handler_and_data(unsigned int irq, irq_flow_handler_t handle,
 				 void *data);
 
+bool irq_has_chained_handler(unsigned int irq);
+
 void irq_modify_status(unsigned int irq, unsigned long clr, unsigned long set);
 
 static inline void irq_set_status_flags(unsigned int irq, unsigned long set)

index e28169dd1c36..826adc1e2c3c 100644
@@ -747,6 +747,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 			mask_ack_irq(desc);
 		irq_state_set_disabled(desc);
 		desc->depth = 1;
+		irq_settings_clr_chained(desc);
 	}
 	desc->handle_irq = handle;
 	desc->name = name;

@@ -755,6 +756,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		irq_settings_set_noprobe(desc);
 		irq_settings_set_norequest(desc);
 		irq_settings_set_nothread(desc);
+		irq_settings_set_chained(desc);
 		irq_startup(desc, true);
 	}
 }

@@ -791,6 +793,15 @@ irq_set_chained_handler_and_data(unsigned int irq, irq_flow_handler_t handle,
 }
 EXPORT_SYMBOL_GPL(irq_set_chained_handler_and_data);
 
+bool irq_has_chained_handler(unsigned int irq)
+{
+	struct irq_desc *desc = irq_to_desc(irq);
+
+	if (!desc)
+		return false;
+	return irq_settings_is_chained(desc);
+}
+
 void
 irq_set_chip_and_handler_name(unsigned int irq, struct irq_chip *chip,
 			      irq_flow_handler_t handle, const char *name)

index 3320b84cc60f..b364dc873314 100644
@@ -15,6 +15,7 @@ enum {
 	_IRQ_NESTED_THREAD	= IRQ_NESTED_THREAD,
 	_IRQ_PER_CPU_DEVID	= IRQ_PER_CPU_DEVID,
 	_IRQ_IS_POLLED		= IRQ_IS_POLLED,
+	_IRQ_IS_CHAINED		= IRQ_IS_CHAINED,
 	_IRQF_MODIFY_MASK	= IRQF_MODIFY_MASK,
 };
 

@@ -154,3 +155,18 @@ static inline bool irq_settings_is_polled(struct irq_desc *desc)
 {
 	return desc->status_use_accessors & _IRQ_IS_POLLED;
 }
+
+static inline void irq_settings_set_chained(struct irq_desc *desc)
+{
+	desc->status_use_accessors |= _IRQ_IS_CHAINED;
+}
+
+static inline void irq_settings_clr_chained(struct irq_desc *desc)
+{
+	desc->status_use_accessors &= ~_IRQ_IS_CHAINED;
+}
+
+static inline bool irq_settings_is_chained(struct irq_desc *desc)
+{
+	return desc->status_use_accessors & _IRQ_IS_CHAINED;
+}

index f8062aaf5df9..e7cc9f199350 100644
@@ -440,6 +440,7 @@ void fixup_irqs(void)
 		int break_affinity = 0;
 		int set_affinity = 1;
 		const struct cpumask *affinity;
+		bool has_user;
 
 		if (!desc)
 			continue;

@@ -451,7 +452,10 @@ void fixup_irqs(void)
 
 		data = irq_desc_get_irq_data(desc);
 		affinity = irq_data_get_affinity_mask(data);
-		if (!irq_has_action(irq) || irqd_is_per_cpu(data) ||
+
+		has_user = irq_has_action(irq) || irq_has_chained_handler(irq);
+
+		if (!has_user || irqd_is_per_cpu(data) ||
 		    cpumask_subset(affinity, cpu_online_mask)) {
 			raw_spin_unlock(&desc->lock);
 			continue;

index e28169dd1c36..b875934768d0 100644
@@ -21,6 +21,20 @@
 
 #include "internals.h"
 
+static irqreturn_t bad_chained_irq(int irq, void *dev_id)
+{
+	WARN_ONCE(1, "Chained irq %d should not call an action\n", irq);
+	return IRQ_NONE;
+}
+
+/*
+ * Chained handlers should never call action on their IRQ. This default
+ * action will emit warning if such thing happens.
+ */
+struct irqaction chained_action = {
+	.handler = bad_chained_irq,
+};
+
 /**
  *	irq_set_chip - set the irq chip for an irq
  *	@irq:	irq number

@@ -746,6 +760,8 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		if (desc->irq_data.chip != &no_irq_chip)
 			mask_ack_irq(desc);
 		irq_state_set_disabled(desc);
+		if (is_chained)
+			desc->action = NULL;
 		desc->depth = 1;
 	}
 	desc->handle_irq = handle;

@@ -755,6 +771,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		irq_settings_set_noprobe(desc);
 		irq_settings_set_norequest(desc);
 		irq_settings_set_nothread(desc);
+		desc->action = &chained_action;
 		irq_startup(desc, true);
 	}
 }

index 5ef0c2dbe930..a44692c8b9f6 100644
@@ -18,6 +18,8 @@
 
 extern bool noirqdebug;
 
+extern struct irqaction chained_action;
+
 /*
  * Bits used by threaded handlers:
  * IRQTF_RUNTHREAD - signals that the interrupt handler thread should run

index e3a8c9577ba6..7d6090519630 100644
@@ -460,7 +460,7 @@ int show_interrupts(struct seq_file *p, void *v)
 	for_each_online_cpu(j)
 		any_count |= kstat_irqs_cpu(i, j);
 	action = desc->action;
-	if (!action && !any_count)
+	if ((!action || action == &chained_action) && !any_count)
 		goto out;
 
 	seq_printf(p, "%*d: ", prec, i);