[PATCH V11] irq: Allow to pass the IRQF_TIMER flag with percpu irq request

[Daniel Lezcano <daniel.lezcano@linaro.org>]

The irq timings infrastructure tracks when the interrupts occur in order to
statistically compute when is supposed to happen an interrupt.

In all the interruptions, it does not make sense to store the timer interrupt
occurences and try to predict the next interrupt as we know the expiration
time.

The request_irq() has a irq flags parameter and the timer drivers use it to
pass the IRQF_TIMER flag, letting us know the interrupt is coming from a timer.
Based on this flag, we can discard these interrupts when tracking them.

But, the API request_percpu_irq does not allow to pass a flag, hence specifying
if the interrupt type is a timer.

Add a function __request_percpu_irq() where we can specify the flags. The
request_percpu_irq() function is changed to be a wrapper to
__request_percpu_irq() passing a zero flag parameter.

For now, in order to prevent a misusage of this parameter, only the IRQF_TIMER
flag (or zero) is a valid parameter to be passed to the
__request_percpu_irq() function.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Mark Rutland <mark.rutland@arm.com>
---
Changelog:

   V11:
	- Drop the changes in the timer drivers and rename the function
	  request_percpu_irq_flags to __request_percpu_irq.
   V10:
	- Drop the change for arch arm virtual timer
	  https://lkml.org/lkml/2017/4/25/184
   V9:
	- Clarified the patch description
	- Fixed EXPORT_SYMBOL_GPL(request_percpu_irq_flags)

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 include/linux/interrupt.h | 11 ++++++++++-
 kernel/irq/manage.c       | 15 ++++++++++-----
 2 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
index 37f8e35..5ac6e23 100644
--- a/include/linux/interrupt.h
+++ b/include/linux/interrupt.h
@@ -152,8 +152,17 @@ request_any_context_irq(unsigned int irq, irq_handler_t handler,
 			unsigned long flags, const char *name, void *dev_id);
 
 extern int __must_check
+__request_percpu_irq(unsigned int irq, irq_handler_t handler,
+		     unsigned long flags, const char *devname,
+		     void __percpu *percpu_dev_id);
+
+static inline int __must_check
 request_percpu_irq(unsigned int irq, irq_handler_t handler,
-		   const char *devname, void __percpu *percpu_dev_id);
+		   const char *devname, void __percpu *percpu_dev_id)
+{
+	return __request_percpu_irq(irq, handler, 0,
+				    devname, percpu_dev_id);
+}
 
 extern const void *free_irq(unsigned int, void *);
 extern void free_percpu_irq(unsigned int, void __percpu *);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 5c11c17..f80baf7 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -1935,9 +1935,10 @@ int setup_percpu_irq(unsigned int irq, struct irqaction *act)
 }
 
 /**
- *	request_percpu_irq - allocate a percpu interrupt line
+ *	__request_percpu_irq - allocate a percpu interrupt line
  *	@irq: Interrupt line to allocate
  *	@handler: Function to be called when the IRQ occurs.
+ *	@flags: Interrupt type flags (IRQF_TIMER only)
  *	@devname: An ascii name for the claiming device
  *	@dev_id: A percpu cookie passed back to the handler function
  *
@@ -1950,8 +1951,9 @@ int setup_percpu_irq(unsigned int irq, struct irqaction *act)
  *	the handler gets called with the interrupted CPU's instance of
  *	that variable.
  */
-int request_percpu_irq(unsigned int irq, irq_handler_t handler,
-		       const char *devname, void __percpu *dev_id)
+int __request_percpu_irq(unsigned int irq, irq_handler_t handler,
+			 unsigned long flags, const char *devname,
+			 void __percpu *dev_id)
 {
 	struct irqaction *action;
 	struct irq_desc *desc;
@@ -1965,12 +1967,15 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
 	    !irq_settings_is_per_cpu_devid(desc))
 		return -EINVAL;
 
+	if (flags && flags != IRQF_TIMER)
+		return -EINVAL;
+
 	action = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
 	if (!action)
 		return -ENOMEM;
 
 	action->handler = handler;
-	action->flags = IRQF_PERCPU | IRQF_NO_SUSPEND;
+	action->flags = flags | IRQF_PERCPU | IRQF_NO_SUSPEND;
 	action->name = devname;
 	action->percpu_dev_id = dev_id;
 
@@ -1991,7 +1996,7 @@ int request_percpu_irq(unsigned int irq, irq_handler_t handler,
 
 	return retval;
 }
-EXPORT_SYMBOL_GPL(request_percpu_irq);
+EXPORT_SYMBOL_GPL(__request_percpu_irq);
 
 /**
  *	irq_get_irqchip_state - returns the irqchip state of a interrupt.
-- 
2.7.4