Re: APIC, changing level/edge interrupt

[Pierre Ossman]

Tim Hockin wrote:

> Of course.  My point was that if it does not, it's a bug in the BIOS.  
>
>  
Something Windows doesn't seem to be affected by so I don't think we'll 
get much help fixing the bios.

> > But since BIOS can configure the APIC then the kernel should be able to 
> >    
>
> Of course, but the kernel has no way to know whether a device should be
> edge or level triggered unless you have a driver for that device.  And
> even if you do, I don't know that there is an API in kernel to say
> set_irq_mode(IRQ_EDGE) (though there could be).
>
>  
There are some calls in the ACPI layer which plays with the level/edge 
stuff but they don't seem very generic. Besides, what I want right now 
is just some possibility of confirming that this level/edge business is 
the cause of all these problems.

> > What is the default mode and what does the XT-PIC expect? (it works fine 
> > with the apic disabled).
> >    
>
> I think default is PIC-compatible which is edge by default.  I think.  I
> don;t have the book here.
>
>  
Ok. The default from the device is level mode which works fine on PIC 
systems. I'm not sure that the hardware actually respects this bit 
because level/pulse mode doesn't make any difference on either PIC or 
APIC systems.

Rgds
Pierre

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