There are some interrupts that are true edge triggered in nature. If not
marked IRQ_PENDING, when disabled, they will be lost.

Use the set_type callback to assign the correct flow type handler for
shared peripheral interrupts.

Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
---
This came to light when a edge triggered interrupt was supposed to wakeup the
sytem. The flow handler was set to the default handle_level_irq. On the resume
path the flow handler was invoked right after the I bit was cleared but before
each individual interrupts were enabled. This made the handle_level_irq ignore
the interrupt (mask_ack it) and it was lost. handle_edge_irq does the right
thing by marking the interrupt as IRQ_PENDING and when the resume code gets to
enabling each interrupt this interrupt is resent again.

 arch/arm/common/gic.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
index e6388dc..a83594a 100644
--- a/arch/arm/common/gic.c
+++ b/arch/arm/common/gic.c
@@ -136,6 +136,9 @@ static int gic_set_type(unsigned int irq, unsigned int type)
 
 	spin_unlock(&irq_controller_lock);
 
+	if ((type & IRQ_TYPE_EDGE_RISING) && gicirq > 31)
+		__set_irq_handler_unlocked(irq, handle_edge_irq);
+
 	return 0;
 }
 
-- 
1.7.1
Sent by an employee of Qualcomm Innovation Center, Inc. Qualcomm Innovation
Center, Inc. is a member of Code Aurora Forum.

--

[ message continues ]

On Thu, Dec 30, 2010 at 10:59 AM, Abhijeet Dharmapurikar

Why does the flow handler hit when the interrupt is disabled?  Have you set
--

[ message continues ]

Since GIC doesnt have disable callback it implements lazy disabling. The 
interrupt is only marked IRQ_DISABLED in the descriptor but is not 
masked in the GIC. Hence the interrupt flow handler is hit.

Now that I re-read the code setting IRQF_NO_SUSPEND would fix the issue. 
But shouldnt set_irq_wake() do something similar?

Do I need to request IRQF_NO_SUSPEND for all the interrupts that could 
possibly wakeup the system - seems a bit unnecessary. IMO the interrupt 
should not be disabled if it is marked IRQF_NO_SUPEND || IRQ_WAKEUP is set.

Abhijeet


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[ message continues ]

Let me correct myself, IRQF_NO_SUSPEND isnt exactly what I want to do. 
If an interrupt triggers after suspend_device_irqs() is run and before 
the I bit is set in arch_suspend_disable_irqs() the system will handle 
the interrupt but will not abort suspend - check_wakeup_irqs() will 
return 0.

IMO, using handle_edge_irq() for an edge triggered wakeup interrupt 
would be the right way to address the issue.

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