Message-ID: <20130805030152.GA23131@zuhnb712>
Date:	Mon, 5 Aug 2013 11:01:52 +0800
From:	Woody Wu <narkewoody@...il.com>
To:	anish kumar <anish198519851985@...il.com>
Cc:	kernelnewbies@...nelnewbies.org, linux-kernel@...r.kernel.org
Subject: Re: How kernel handle interrupts[AX88796B network controller]

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:
> > On Fri, Dec 21, 2012 at 01:33:03PM -0800, anish kumar wrote:
> > > On Fri, 2012-12-21 at 23:34 +0800, Woody Wu wrote:
> > > > On Thu, Dec 20, 2012 at 10:05:05AM -0800, anish singh wrote:
> > > > > On Dec 20, 2012 6:30 AM, "Woody Wu" <narkewoody@...il.com> wrote:
> > > > > >
> > > > > > 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.
> > > > > >
> > > > > > 2. My device, an AX88796B network controller, asserting the interrupt
> > > > > >    line in a level-triggered manner. Now I met problem with the device
> > > > > that
> > > > > >    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!

> > 
> > 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.
> > 
> > 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.
> > 
> > 
> > > > 
> > > > Thanks.
> > > > 
> > > > > >
> > > > > >
> > > > > > Thanks in advance.
> > > > > >
> > > > > > --
> > > > > > woody
> > > > > > I can't go back to yesterday - because I was a different person then.
> > > > > >
> > > > > > _______________________________________________
> > > > > > Kernelnewbies mailing list
> > > > > > Kernelnewbies@...nelnewbies.org
> > > > > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> > > > 
> > > 
> > 
> 

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