Re: Why no interrupt priorities?

Richard B. Johnson
2004-02-27T13:44:35Z

On Fri, 27 Feb 2004, Michael Frank wrote:

> On Fri, 27 Feb 2004 09:05:48 +0000, Russell King <rmk+lkml@arm.linux.org.uk> wrote:
>
> > On Fri, Feb 27, 2004 at 02:26:31PM +0800, Michael Frank wrote:
> >> Is this to imply that edge triggered shared interrupts are used anywhere?
> >
> > It is (or used to be) rather common with serial ports. Remember that
> > COM1 and COM3 were both defined to use IRQ4 and COM2 and COM4 to use
> > IRQ3.
> >
> >> Never occured to me to use shared IRQ's edge triggered as this mode
> >> _cannot_ work reliably for HW limitations.
> >
> > The serial driver takes great care with this - when we service such an
> > interrupt, we keep going until we have scanned all the devices until
> > such time that we can say "all devices are no longer signalling an
> > interrupt".
> >
> > This is something it has always done - it's nothing new.
> >
>
> Sorry, i think the serial driver IRQ is level triggered :)

CPU0 CPU1
0: 7904936 7922491 IO-APIC-edge timer
1: 74277 70096 IO-APIC-edge keyboard
2: 0 0 XT-PIC cascade
3: 535 556 IO-APIC-edge serial <--- EDGE
4: 2 1 IO-APIC-edge serial <--- EDGE
10: 3435637 3440251 IO-APIC-level eth0
11: 295018 296838 IO-APIC-level BusLogic BT-958
13: 4567 4591 IO-APIC-level Analogic(tm) AMX/AFF Driver
14: 1331 1239 IO-APIC-level Analogic(tm) DSP/DSS Driver
15: 2 3 IO-APIC-level Analogic(tm) VXI/MSG Driver
NMI: 0 0
LOC: 15826338 15826337
ERR: 0
MIS: 2

Cheers,
Dick Johnson
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