Re: hwo to adjust interrupt?

[Ming Zhang <mingz@ele.uri.edu>]

ic. thanks a lot for explanation.

so these are level sensitive interrupt.

i need to find a hw book now...

Ming

On Mon, 2005-08-15 at 11:47 -0700, Bryan Henderson wrote:
> >so it is possible that both card raise intr quicker than isr run, then
> >both isr will do mmio and go ahead, but then what is
> >
> >device 1 raise intr
> >device 2 isr run and not belong to it, so quit, but before it clear intr
> >and quit
> >device 2 raise intr
> >device 1 isr run and handle device 1, then clear intr and quit.
> >
> >then device 2 intr lost?
> 
> As these are level sensitive interrupt requests, they can't be lost.  As 
> long as Device 2 is requesting service,
> the shared IRQ is raised and at some point Linux will call Device 2's 
> interrupt handler.  Either the first level IRQ handler will keep calling 
> all the interrupt handlers that service that IRQ until the IRQ subsides, 
> or it will unmask the IRQ, causing an immediate new interrupt and the 
> first level interrupt handler runs again and calls all the device drivers 
> again.
> 
> The raised IRQ says, "Device 1 or Device 2 needs service."  The device 
> drivers clear the service request of the individual device; as long as 
> either device requests service, the IRQ is raised.
> 
> --
> Bryan Henderson                     IBM Almaden Research Center
> San Jose CA                         Filesystems
> 
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