4 files changed, 39 insertions, 1 deletions

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 5e7c6ee8c35c..ce8171bc6fac 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -101,6 +101,9 @@ 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
  */
@@ -124,6 +127,9 @@ 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);
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index b08c0d24f202..f856330e684a 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -580,6 +580,7 @@ __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? */
@@ -599,6 +600,7 @@ __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 d7f7b5fd2476..0a3fd5b524c9 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);
 
@@ -468,12 +473,14 @@ static int irq_wait_for_interrupt(struct irqaction *action)
  */
 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
@@ -904,7 +911,14 @@ 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);
 
@@ -1011,7 +1025,10 @@ 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);