5 files changed, 194 insertions, 9 deletions

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 35e7df1e9f30..1ac57e522a1f 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -50,6 +50,9 @@
  * IRQF_IRQPOLL - Interrupt is used for polling (only the interrupt that is
  *                registered first in an shared interrupt is considered for
  *                performance reasons)
+ * IRQF_ONESHOT - Interrupt is not reenabled after the hardirq handler finished.
+ *                Used by threaded interrupts which need to keep the
+ *                irq line disabled until the threaded handler has been run.
  */
 #define IRQF_DISABLED           0x00000020
 #define IRQF_SAMPLE_RANDOM      0x00000040
@@ -59,6 +62,7 @@
 #define IRQF_PERCPU             0x00000400
 #define IRQF_NOBALANCING        0x00000800
 #define IRQF_IRQPOLL            0x00001000
+#define IRQF_ONESHOT            0x00002000
 
 /*
  * Bits used by threaded handlers:
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 9e9eb76faf81..ae9653dbcd78 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -69,6 +69,8 @@ typedef	void (*irq_flow_handler_t)(unsigned int irq,
 #define IRQ_MOVE_PCNTXT         0x01000000      /* IRQ migration from process context */
 #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)
@@ -100,6 +102,9 @@ struct msi_desc;
  * @set_type:           set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
  * @set_wake:           enable/disable power-management wake-on of an IRQ
  *
+ * @bus_lock:           function to lock access to slow bus (i2c) chips
+ * @bus_sync_unlock:    function to sync and unlock slow bus (i2c) chips
+ *
  * @release:            release function solely used by UML
  * @typename:           obsoleted by name, kept as migration helper
  */
@@ -123,6 +128,9 @@ struct irq_chip {
         int             (*set_type)(unsigned int irq, unsigned int flow_type);
         int             (*set_wake)(unsigned int irq, unsigned int on);
 
+        void            (*bus_lock)(unsigned int irq);
+        void            (*bus_sync_unlock)(unsigned int irq);
+
         /* Currently used only by UML, might disappear one day.*/
 #ifdef CONFIG_IRQ_RELEASE_METHOD
         void            (*release)(unsigned int irq, void *dev_id);
@@ -373,6 +381,8 @@ 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 13c68e71b726..c1660194d115 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
@@ -382,7 +449,10 @@ handle_level_irq(unsigned int irq, struct irq_desc *desc)
 
         spin_lock(&desc->lock);
         desc->status &= ~IRQ_INPROGRESS;
-        if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
+
+        if (unlikely(desc->status & IRQ_ONESHOT))
+                desc->status |= IRQ_MASKED;
+        else if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
                 desc->chip->unmask(irq);
 out_unlock:
         spin_unlock(&desc->lock);
@@ -572,6 +642,7 @@ __set_irq_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
                 desc->chip = &dummy_irq_chip;
         }
 
+        chip_bus_lock(irq, desc);
         spin_lock_irqsave(&desc->lock, flags);
 
         /* Uninstall? */
@@ -591,6 +662,7 @@ __set_irq_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
                 desc->chip->startup(irq);
         }
         spin_unlock_irqrestore(&desc->lock, flags);
+        chip_bus_sync_unlock(irq, desc);
 }
 EXPORT_SYMBOL_GPL(__set_irq_handler);
 
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index e70ed5592eb9..1b5d742c6a77 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -44,6 +44,19 @@ extern int irq_select_affinity_usr(unsigned int irq);
 
 extern void irq_set_thread_affinity(struct irq_desc *desc);
 
+/* Inline functions for support of irq chips on slow busses */
+static inline void chip_bus_lock(unsigned int irq, struct irq_desc *desc)
+{
+        if (unlikely(desc->chip->bus_lock))
+                desc->chip->bus_lock(irq);
+}
+
+static inline void chip_bus_sync_unlock(unsigned int irq, struct irq_desc *desc)
+{
+        if (unlikely(desc->chip->bus_sync_unlock))
+                desc->chip->bus_sync_unlock(irq);
+}
+
 /*
  * Debugging printout:
  */
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 0ec9ed831737..bde4c667d24d 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -230,9 +230,11 @@ void disable_irq_nosync(unsigned int irq)
         if (!desc)
                 return;
 
+        chip_bus_lock(irq, desc);
         spin_lock_irqsave(&desc->lock, flags);
         __disable_irq(desc, irq, false);
         spin_unlock_irqrestore(&desc->lock, flags);
+        chip_bus_sync_unlock(irq, desc);
 }
 EXPORT_SYMBOL(disable_irq_nosync);
 
@@ -294,7 +296,8 @@ void __enable_irq(struct irq_desc *desc, unsigned int irq, bool resume)
  *      matches the last disable, processing of interrupts on this
  *      IRQ line is re-enabled.
  *
- *      This function may be called from IRQ context.
+ *      This function may be called from IRQ context only when
+ *      desc->chip->bus_lock and desc->chip->bus_sync_unlock are NULL !
  */
 void enable_irq(unsigned int irq)
 {
@@ -304,9 +307,11 @@ void enable_irq(unsigned int irq)
         if (!desc)
                 return;
 
+        chip_bus_lock(irq, desc);
         spin_lock_irqsave(&desc->lock, flags);
         __enable_irq(desc, irq, false);
         spin_unlock_irqrestore(&desc->lock, flags);
+        chip_bus_sync_unlock(irq, desc);
 }
 EXPORT_SYMBOL(enable_irq);
 
@@ -436,6 +441,26 @@ int __irq_set_trigger(struct irq_desc *desc, unsigned int irq,
         return ret;
 }
 
+/*
+ * Default primary interrupt handler for threaded interrupts. Is
+ * assigned as primary handler when request_threaded_irq is called
+ * with handler == NULL. Useful for oneshot interrupts.
+ */
+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()) {
@@ -451,6 +476,23 @@ static int irq_wait_for_interrupt(struct irqaction *action)
         return -1;
 }
 
+/*
+ * Oneshot interrupts keep the irq line masked until the threaded
+ * handler finished. unmask if the interrupt has not been disabled and
+ * is marked MASKED.
+ */
+static void irq_finalize_oneshot(unsigned int irq, struct irq_desc *desc)
+{
+        chip_bus_lock(irq, desc);
+        spin_lock_irq(&desc->lock);
+        if (!(desc->status & IRQ_DISABLED) && (desc->status & IRQ_MASKED)) {
+                desc->status &= ~IRQ_MASKED;
+                desc->chip->unmask(irq);
+        }
+        spin_unlock_irq(&desc->lock);
+        chip_bus_sync_unlock(irq, desc);
+}
+
 #ifdef CONFIG_SMP
 /*
  * Check whether we need to change the affinity of the interrupt thread.
@@ -492,7 +534,7 @@ static int irq_thread(void *data)
         struct sched_param param = { .sched_priority = MAX_USER_RT_PRIO/2, };
         struct irqaction *action = data;
         struct irq_desc *desc = irq_to_desc(action->irq);
-        int wake;
+        int wake, oneshot = desc->status & IRQ_ONESHOT;
 
         sched_setscheduler(current, SCHED_FIFO, &param);
         current->irqaction = action;
@@ -518,6 +560,9 @@ static int irq_thread(void *data)
                         spin_unlock_irq(&desc->lock);
 
                         action->thread_fn(action->irq, action->dev_id);
+
+                        if (oneshot)
+                                irq_finalize_oneshot(action->irq, desc);
                 }
 
                 wake = atomic_dec_and_test(&desc->threads_active);
@@ -565,7 +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)
@@ -590,10 +635,32 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
                 rand_initialize_irq(irq);
         }
 
+        /* Oneshot interrupts are not allowed with shared */
+        if ((new->flags & IRQF_ONESHOT) && (new->flags & IRQF_SHARED))
+                return -EINVAL;
+
+        /*
+         * 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;
+        }
+
         /*
-         * Threaded 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,
@@ -662,9 +729,12 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
                         desc->status |= IRQ_PER_CPU;
 #endif
 
-                desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING |
+                desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
                                   IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);
 
+                if (new->flags & IRQF_ONESHOT)
+                        desc->status |= IRQ_ONESHOT;
+
                 if (!(desc->status & IRQ_NOAUTOEN)) {
                         desc->depth = 0;
                         desc->status &= ~IRQ_DISABLED;
@@ -875,7 +945,14 @@ EXPORT_SYMBOL_GPL(remove_irq);
  */
 void free_irq(unsigned int irq, void *dev_id)
 {
+        struct irq_desc *desc = irq_to_desc(irq);
+
+        if (!desc)
+                return;
+
+        chip_bus_lock(irq, desc);
         kfree(__free_irq(irq, dev_id));
+        chip_bus_sync_unlock(irq, desc);
 }
 EXPORT_SYMBOL(free_irq);
 
@@ -884,6 +961,8 @@ EXPORT_SYMBOL(free_irq);
  *      @irq: Interrupt line to allocate
  *      @handler: Function to be called when the IRQ occurs.
  *                Primary handler for threaded interrupts
+ *                If NULL and thread_fn != NULL the default
+ *                primary handler is installed
  *      @thread_fn: Function called from the irq handler thread
  *                  If NULL, no irq thread is created
  *      @irqflags: Interrupt type flags
@@ -963,8 +1042,12 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
 
         if (desc->status & IRQ_NOREQUEST)
                 return -EINVAL;
-        if (!handler)
-                return -EINVAL;
+
+        if (!handler) {
+                if (!thread_fn)
+                        return -EINVAL;
+                handler = irq_default_primary_handler;
+        }
 
         action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
         if (!action)
@@ -976,7 +1059,10 @@ int request_threaded_irq(unsigned int irq, irq_handler_t handler,
         action->name = devname;
         action->dev_id = dev_id;
 
+        chip_bus_lock(irq, desc);
         retval = __setup_irq(irq, desc, action);
+        chip_bus_sync_unlock(irq, desc);
+
         if (retval)
                 kfree(action);