[Linux-parport] late parport interrupts

Anton Wilson anton.wilson at camotion.com
Mon Oct 3 12:48:35 EDT 2005


i'm running a custom parport driver that does nothing much but register 
an interrupt handler. I hooked up my PC to a signal
generator generating a signal at 1000 hz. It works fine most of the 
time, but I'm get a late interrupt once or twice a second on
the order of 1,300 microseconds when it should be around 1000 
microseconds. This is hen followed by another on-time
parport interrupt (700 microseconds from the late one).

The signal on the oscilloscope seems fine. I disabled Ethernet, enabled 
unmasking of hard drive interrupts, forced the hard drive
to use dma. The only other interrupts occurring on the system according 
to /proc/interrupts are the timer, the keyboard, and the
mouse. I even changed the parport_pc driver to register interrupts with 
SA_INTERRUPT to disable interrupts while processing.
None of these things have helped.

Can anyone think of another reason why parport_pc_interrupt would get 
called a few hundred microseconds late 2 or 3 times a second?


Anton Wilson
CAMotion INC.

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