How kernel handle interrupts

[anish kumar]

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.
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)
> 
> 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.
> 
> 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.
> > >
> > > _______________________________________________
> > > Kernelnewbies mailing list
> > > Kernelnewbies at kernelnewbies.org
> > > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> 
>