Setting GPIO to trigger interrupt on mpc85xx

Kenny Ho kho at
Sat Jan 22 07:47:20 EST 2011



I am working on the fsl P1020rdb kit with the 2.6.32 linux kernel that
came with the kit and I am trying to get an GPIO to trigger an
interrupt.  I am fairly new and have been stumbling for quite a bit with
no success so I am hoping some of you experts out there can give me some




**What I have tried so far**:


I am implementing the interrupt setup on my custom GPIO module during
its init.  I started following the information available in Linux Device
Drivers, Third Edition but it turns out to be out of date or
incompatible with the ppc platform.  (The device tree, the hwirq to virq
mapping... even though the number turns out to be the same for GPIO,


Initially I was only calling request_irq but I got ENOSYS.  That was
solved by calling irq_create_mapping but then the module init was stuck
at the request_irq (with the isr continuously being called.)  That was
resolved when I ended up using the device tree by calling
irq_of_parse_and_map and using set_irq_handler before calling
request_irq.   Now the module successfully init and I can see the isr
entry in /proc/interrupt but when I physically toggle my GPIO pin, the
handler set by set_irq_handler was being called continuously (and then
crash) while the isr set by request_irq was never called. 


Another thing I don't understand is that the /proc/interrupt entry say
the gpio interrupt is OpenPIC Level when the GPIO interrupt is suppose
to be edge only (either falling only or both.)  My dts interrupt entry
for the GPIO is <47 2>, which should indicates edge trigger right?



**My questions**:

What are the relationship between set_irq_handler, set_irq_type and
request_irq?  Are the first two supposed to be a replacement of the 3rd
or are they suppose to be used concurrently?


What are the differences between the handler set by set_irq_handler and
the isr set by request_irq?  Which one is called first?  Or should only
one of them get set at all time?


(I was reading
html but I am still very confused.)


Which signals are those IRQ type referring to?  Are they referring to
the triggering signal (GPIO in my case) or the PIC signal to the cpu


What are the things I need to do in the IRQ handler/isr to terminate an
interrupt?  I know I need to clear the event register (which is GPIER in
my case) which I have done but that didn't stop the handler from getting
call again.  Must I also disable the interrupt?  For the isr set by
request_irq, I also return IRQ_HANDLED... is that sufficient?


For the handler set by set_irq_handler, do I need to call other handler?
I noticed there are generic_handle_irq and handle_(level/edge,
etc)_irq... am I suppose to call those to terminate an interrupt?  I
also noticed there are eoi() and end() in desc->chip.  (I assume those
are for the PIC)... am I suppose to call those as well?



As you can see... I am very much confused and have lots of questions.
Any help from you folks is much appreciated.



Kenny Ho




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