Re: [PATCH] GIC: Assign correct flow handler type in set_type callback

From: Abhijeet Dharmapurikar
Date: Sun Jan 02 2011 - 01:27:17 EST

On 12/31/2010 02:39 AM, Abhijeet Dharmapurikar wrote:
On 12/29/2010 10:27 PM, Rabin Vincent wrote:
On Thu, Dec 30, 2010 at 10:59 AM, Abhijeet Dharmapurikar
<adharmap@xxxxxxxxxxxxxx> wrote:
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@xxxxxxxxxxxxxx>
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

Why does the flow handler hit when the interrupt is disabled? Have you
IRQF_NOSUSPEND on this interrupt?

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.

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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