3 files changed, 101 insertions, 3 deletions

diff --git a/include/linux/irq.h b/include/linux/irq.h
index ce8171bc6fac..8778ee993937 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -70,6 +70,7 @@ typedef	void (*irq_flow_handler_t)(unsigned int irq,
 #define IRQ_AFFINITY_SET        0x02000000      /* IRQ affinity was set from userspace*/
 #define IRQ_SUSPENDED           0x04000000      /* IRQ has gone through suspend sequence */
 #define IRQ_ONESHOT             0x08000000      /* IRQ is not unmasked after hardirq */
+#define IRQ_NESTED_THREAD       0x10000000      /* IRQ is nested into another, no own handler thread */
 
 #ifdef CONFIG_IRQ_PER_CPU
 # define CHECK_IRQ_PER_CPU(var) ((var) & IRQ_PER_CPU)
@@ -386,6 +387,8 @@ set_irq_chained_handler(unsigned int irq,
         __set_irq_handler(irq, handle, 1, NULL);
 }
 
+extern void set_irq_nested_thread(unsigned int irq, int nest);
+
 extern void set_irq_noprobe(unsigned int irq);
 extern void set_irq_probe(unsigned int irq);
 
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index f856330e684a..5765aad94998 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -222,6 +222,34 @@ int set_irq_chip_data(unsigned int irq, void *data)
 }
 EXPORT_SYMBOL(set_irq_chip_data);
 
+/**
+ *      set_irq_nested_thread - Set/Reset the IRQ_NESTED_THREAD flag of an irq
+ *
+ *      @irq:   Interrupt number
+ *      @nest:  0 to clear / 1 to set the IRQ_NESTED_THREAD flag
+ *
+ *      The IRQ_NESTED_THREAD flag indicates that on
+ *      request_threaded_irq() no separate interrupt thread should be
+ *      created for the irq as the handler are called nested in the
+ *      context of a demultiplexing interrupt handler thread.
+ */
+void set_irq_nested_thread(unsigned int irq, int nest)
+{
+        struct irq_desc *desc = irq_to_desc(irq);
+        unsigned long flags;
+
+        if (!desc)
+                return;
+
+        spin_lock_irqsave(&desc->lock, flags);
+        if (nest)
+                desc->status |= IRQ_NESTED_THREAD;
+        else
+                desc->status &= ~IRQ_NESTED_THREAD;
+        spin_unlock_irqrestore(&desc->lock, flags);
+}
+EXPORT_SYMBOL_GPL(set_irq_nested_thread);
+
 /*
  * default enable function
  */
@@ -299,6 +327,45 @@ static inline void mask_ack_irq(struct irq_desc *desc, int irq)
         }
 }
 
+/*
+ *      handle_nested_irq - Handle a nested irq from a irq thread
+ *      @irq:   the interrupt number
+ *
+ *      Handle interrupts which are nested into a threaded interrupt
+ *      handler. The handler function is called inside the calling
+ *      threads context.
+ */
+void handle_nested_irq(unsigned int irq)
+{
+        struct irq_desc *desc = irq_to_desc(irq);
+        struct irqaction *action;
+        irqreturn_t action_ret;
+
+        might_sleep();
+
+        spin_lock_irq(&desc->lock);
+
+        kstat_incr_irqs_this_cpu(irq, desc);
+
+        action = desc->action;
+        if (unlikely(!action || (desc->status & IRQ_DISABLED)))
+                goto out_unlock;
+
+        desc->status |= IRQ_INPROGRESS;
+        spin_unlock_irq(&desc->lock);
+
+        action_ret = action->thread_fn(action->irq, action->dev_id);
+        if (!noirqdebug)
+                note_interrupt(irq, desc, action_ret);
+
+        spin_lock_irq(&desc->lock);
+        desc->status &= ~IRQ_INPROGRESS;
+
+out_unlock:
+        spin_unlock_irq(&desc->lock);
+}
+EXPORT_SYMBOL_GPL(handle_nested_irq);
+
 /**
  *      handle_simple_irq - Simple and software-decoded IRQs.
  *      @irq:   the interrupt number
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0a3fd5b524c9..e485cea04bf1 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -451,6 +451,16 @@ static irqreturn_t irq_default_primary_handler(int irq, void *dev_id)
         return IRQ_WAKE_THREAD;
 }
 
+/*
+ * Primary handler for nested threaded interrupts. Should never be
+ * called.
+ */
+static irqreturn_t irq_nested_primary_handler(int irq, void *dev_id)
+{
+        WARN(1, "Primary handler called for nested irq %d\n", irq);
+        return IRQ_NONE;
+}
+
 static int irq_wait_for_interrupt(struct irqaction *action)
 {
         while (!kthread_should_stop()) {
@@ -600,7 +610,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
         struct irqaction *old, **old_ptr;
         const char *old_name = NULL;
         unsigned long flags;
-        int shared = 0;
+        int nested, shared = 0;
         int ret;
 
         if (!desc)
@@ -630,9 +640,27 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
                 return -EINVAL;
 
         /*
-         * Threaded handler ?
+         * Check whether the interrupt nests into another interrupt
+         * thread.
+         */
+        nested = desc->status & IRQ_NESTED_THREAD;
+        if (nested) {
+                if (!new->thread_fn)
+                        return -EINVAL;
+                /*
+                 * Replace the primary handler which was provided from
+                 * the driver for non nested interrupt handling by the
+                 * dummy function which warns when called.
+                 */
+                new->handler = irq_nested_primary_handler;
+        }
+
+        /*
+         * Create a handler thread when a thread function is supplied
+         * and the interrupt does not nest into another interrupt
+         * thread.
          */
-        if (new->thread_fn) {
+        if (new->thread_fn && !nested) {
                 struct task_struct *t;
 
                 t = kthread_create(irq_thread, new, "irq/%d-%s", irq,