[RFC PATCH] genirq: set pending flag for disabled level interrupt

[Abhijeet Dharmapurikar <adharmap@codeaurora.org>]

For hardware which has no wakeup source configuration facility, it needs
its wakeup interrupts unmasked.
If a wakeup edge interrupt triggered while the system was suspending the
edge flow handler marks it pending and masks the interrupt. The kernel
checks pending flag on wakeup interrupts and aborts suspend if one is set.

If a wakeup level interrupt triggered while the system was suspending the
level flow handler masks the interrupt without setting the pending flag.
Suspend won't be aborted. This is fine as it is expected that a level
triggered interrupt will stay triggered and cause the system to resume.
This however doesn't work on chips that don't have wakeup configuration
in hardware because such chips need that interrupt unmasked for causing
a resume.

Address that shortcoming by making the level flow handler set the pending
flag if a wakeup interrupt controlled by such a chip is triggered while
it is suspended.

Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
---
If a level interrupt irq triggered right while the system was doing
suspend_noirqs, the level flow handler will mask that interrupt and when the
system went in to power collapse the interrupt controller did not wakeup the
phone. The interrupt controller needs an interrupt triggered and masked to
wakeup the phone - it does not have any wakeup interrupt configuration.
The solution presented here is to mark that level triggered
wakeup interrupt pending for chips with IRQCHIP_MASK_ON_SUSPEND. This will cause
check_wakeup_irqs to abort suspend.
Other solution would be to unmask such level interrupt in check_wakeup_irqs()
but that seemed like I was expanding and complicating check_wakeup_irqs()
duties - let me know if you think otherwise. 
Note that we cannot unmask the interrupt in the level flow handler, that will
cause an interrupt storm.

 include/linux/irq.h |    4 +++-
 kernel/irq/chip.c   |   16 +++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 87a06f3..0019385 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -332,7 +332,9 @@ struct irq_chip {
  *
  * IRQCHIP_SET_TYPE_MASKED:	Mask before calling chip.irq_set_type()
  * IRQCHIP_EOI_IF_HANDLED:	Only issue irq_eoi() when irq was handled
- * IRQCHIP_MASK_ON_SUSPEND:	Mask non wake irqs in the suspend path
+ * IRQCHIP_MASK_ON_SUSPEND:	Mask non wake irqs in the suspend path,
+ *				mark wakeup level interrupts pending
+ *				if suspended and triggered
  * IRQCHIP_ONOFFLINE_ENABLED:	Only call irq_on/off_line callbacks
  *				when irq enabled
  */
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index d5a3009..0199871 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -339,9 +339,23 @@ handle_level_irq(unsigned int irq, struct irq_desc *desc)
 	 * If its disabled or no action available
 	 * keep it masked and get out of here
 	 */
-	if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data)))
+	if (unlikely(!desc->action))
 		goto out_unlock;
 
+	if (irqd_irq_disabled(&desc->irq_data)) {
+		/*
+		 * Hardware which has no wakeup source configuration facility,
+		 * needs its wakeup interrupts unmasked and triggered to cause
+		 * a wakeup. Since the interrupt will be masked, mark it pending
+		 * if it were suspended so that suspend will be aborted later.
+		 */
+		if (desc->istate & IRQS_SUSPENDED &&
+		    irqd_is_wakeup_set(&desc->irq_data) &&
+		    irq_desc_get_chip(desc)->flags & IRQCHIP_MASK_ON_SUSPEND)
+			desc->istate |= IRQS_PENDING;
+		goto out_unlock;
+	}
+
 	handle_irq_event(desc);
 
 	if (!irqd_irq_disabled(&desc->irq_data) && !(desc->istate & IRQS_ONESHOT))
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.