How kernel handle interrupts

[Woody Wu]

在 2012-12-21 PM6:53，"anish kumar" <anish198519851985 at gmail.com>写道：
>
> On Fri, 2012-12-21 at 17:34 +0800, Woody Wu wrote:
> >
> > 在 2012-12-21 AM2:05，"anish singh" <anish198519851985 at gmail.com>写
> > 道：
> > >
> > >
> > > On Dec 20, 2012 6:30 AM, "Woody Wu" <narkewoody at gmail.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.
> >
> > Sorry not fully understand . My device is an interrupt line is back to
> > inactive.Ethernet controller. It needs to response TX and RX
> > interrupts triggered by the device itself. In this case , my driver is
> > a chip driver or interrupt controller driver in your terms?
> Your device is neither of these.
> >
> > If my driver needs to do the mask and unmask job, what's the kernel
> > API I should call?
> You don't need to worry about mask and unmask job AFAIK.
> >
> > And , I don't understand why there exists differences between level
> > and edge triggered interrupts in terms of kernel handling.
> Level type interrupts are active as long as the hardware line has the
> active level. This may require to mask the interrupt and unmask it after
> the associated handler has acknowledged the device, so the interrupt
> line is back to inactive.

This is a little confusing. You just said I don't need to worry mask and
unmask things. But now you say I need to for the level triggered
interrupts...  And, what's the mask and unmask APIs that I can call?

> Edge interrupt occurs on the falling and/or rising edge of a hardware
> signal.The occurrence is latched into the irq controller hardware
> and must be acked in order to be re-enabled.
> Read the code /kerel/irq/chip.c(handle_edge_irq & handle_level_irq)

Thanks for pointing me there.

> >
> > I know my questions might be basic , so would please tell me what's
> If it was not basic then this question wouldn't be in kernelnewbies
> right :)?
> >  the kernel code for ARM architecture doing these complex jobs as you
> > explained?
> You don't need to worry about it but if you want to know further then I
> suggest tracing the call flow from asm interrupt handler(I believe
> do_irq but not sure) in arm to handle_edge_irq call flow by adding some
> logs or just browsing the code.

Okay I will be reading the code. If you have time please also be kind to
help answer my previous questions in this message. Thanks a lot!

> >
> > Thanks in advance !
> >
> > >
> > > >
> > > > 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.
> > >
> > > >
> > > >
> > > > Thanks in advance.
> > > >
> > > > --
> > > > woody
> > > > I can't go back to yesterday - because I was a different person
> > then.
> > > >
> > > > _______________________________________________
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> >
> >
>
>
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