From: pdh@netcom.com (P D H) Subject: Re: [Q]: 2 Serial Ports on one IRQ Date: Thu, 29 Apr 1993 23:17:29 GMT
wong@cs.tu-berlin.de (Wolfgang Jung) writes:
>Now if I use only One line per IRQ everything works fine
>But if I use 2 lines on one of the IRQ's (ie ttys3 & ttys1)
>It only works if there is activity on ttys1 .
>
>Where do I have to look for the Problem ?
The problem is hardware and the board for ttys1 is the culprit.
Sharing IRQs requires a number of ducks to be lined up just perfectly.
Among them is that EVERY board touching that IRQ line on the bus must
NOT put any load on the line, otherwise it can basically "suck out
the interrupts" from the other boards. Since ttys1 works, it suggests
that the board for ttys3 is not affecting it. Since ttys3 fails, it
suggests the board for ttys1 is screwing your interrupts.
>Is it a bug in the serialdrivers, which are unable to handle
>shared interupts or is this the hardware which dowsnot support
>it ? (At least it seems that this is now hardware Problem since
>everything works wonderful if I use only 1 Line per iRQ line?
Use 1 IRQ per port or get better hardware.
>(I could use a workaround if I take 1 interupt for each line,
>but I dont want to spoil interups :-(
>
>So could soembody help me with this ?
See above. Also check to see if you can use any extended (8-15) IRQs.
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