Re: can someone explain...[ PCI interrupts]

From: Scott Long <scottl_at_samsco.org>
Date: Wed, 07 Dec 2005 11:07:28 -0700
M. Warner Losh wrote:

> In message: <018e01c5fafe$c9154a20$642a15ac_at_smiley>
>             "Darren Pilgrim" <darren.pilgrim_at_bitfreak.org> writes:
> : From: John Baldwin
> : > 
> : > The reason [for masking interrupts] is that PCI interrupts are level
> : > triggered, so they won't "shut up" until the ISR has run and pacified
> : > the PCI device.
> : 
> : But PCI interrupts can be programmed either level- or edge-triggered, so
> : wouldn't programming to edge-triggered interrupts solve the "they won't shut
> : up" issue?
> 
> PCI interrupts are level.  There's no way to program them otherwise.
> 
> Warner

While electrically they are level, the APIC can be programmed to pass
them on either level or edge.  Once you get into MSI, the distinction
becomes very muddy.

Scott
Received on Wed Dec 07 2005 - 17:07:40 UTC

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