On Mon, Jan 07, 2013 at 10:06:30PM +0530, anish kumar wrote:

On Sat, 2012-12-22 at 23:11 +0800, Woody Wu wrote:

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On Fri, Dec 21, 2012 at 01:33:03PM -0800, anish kumar wrote:

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On Fri, 2012-12-21 at 23:34 +0800, Woody Wu wrote:

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On Thu, Dec 20, 2012 at 10:05:05AM -0800, anish singh wrote:

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On Dec 20, 2012 6:30 AM, "Woody Wu" [off-list ref] wrote:

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Hi, List

Where is the Kernel code that handles external interrupts? I want to
have a look at it but haven't found out where it is.

Actually, I have some basic questions about interrupt handling in Linux.
1. After Kernel's ISR received an interrupt, I believe it will invoke a
   handler defined in a device driver if any. But it should be the
   device driver's responsibility or kernel ISR's responsibility to
   clear (or acknowledge) the interrupt?

If the interrupt in question is currently being handled then in
the case of edge triggered interrupt we just mask the interrupt,set it
pending and bail out.Once the interrupt handler completes then we check for
pending interrupt and handle it.In level triggered we don't do that.
Kerenel ISR -this is mixture of core kernel interrupt handling code + your
device driver interrupt handler(if this is chip driver which is supposed to
get one interrupt and is reponsible for calling other interrupt handlers
based on the chip register status then you do explicit masking unmasking
yourself).
If you device driver is a interrupt controller driver then you register
your driver with kernel interrupt handling code and need to write some
callbacks such as .mask,.unmask and so on.This callbacks are called at
appropiate places whenever the interrupt is raised.This interrupt is then
passed to drivers who has requested for this interrupt by calling
request_irq.

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2. My device, an AX88796B network controller, asserting the interrupt
   line in a level-triggered manner. Now I met problem with the device

that

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   might caused by the CPU interrupt mode is not set as level-triggered by
   edge trigger.  My CPU is Samsung S3C2410, an ARM920T powered one.  Does
   anyone know usually where and how should I do this kind of setting?

Just pass the parameter "level triggered" in request_irq in your device
driver.

Hi Sign,

I searched the interrupt.h for the all the defined flags that I can pass
to the request_irq, but there is no a flag looks like "level triggered".
Would you tell me what you mean the parameter "level triggered"?

irq_set_irq_type(info->irq, IRQ_TYPE_LEVEL_LOW)

include/linux/irq.h
IRQ_TYPE_LEVEL_HIGH          - high level triggered
IRQ_TYPE_LEVEL_LOW           - low level triggered

Thanks. Now I find the function.

I searched some code about irq in ARM architecure.  Some other
people talked about do_IRQ() probabaly is wrong for ARM. There is simply
no that function in ARM. Maybe the do_IRQ in x86 is replaced by
handle_IRQ.

arch/arm/kernel/entry-armv.S
__irq_svc is called by the arm processor which in turn calls irq_handler
macro.I think this is the lowest level handler after which linux
interrupt handling takes over.

Only today, I saw this email you replied. Many thanks!

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For the irq_set_irq_type(), do you think what's the correct place to
call it? Inside my device driver or outside the device driver (probably
in the board definition file)? If that should be called inside a device
driver, should it be the driver probe function or in the open function?
After or before the invocation of request_irq()?

irq_set_irq_type() should be called by device driver code not by the
board file.It should be called in the probe function AFAIK.

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Sorry for asking too many question.  I found the kernel + device driver
irq handling part still not clear to me.

You are welcome to ask as many question as you want.

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Thanks.

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Thanks in advance.

--
woody
I can't go back to yesterday - because I was a different person then.

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-- 
I can't go back to yesterday - because I was a different person then