Subject: Re: MSI support on Linux PCI implementation for Ocotea

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sat, 17 Jun 2006 08:13:17 +1000

On Fri, 2006-06-16 at 14:45 -0700, Shawn Jin wrote:
> Hi Ben,
> 
> > Now, regarding MSI, as you have noticed, the situation isn't great. I'm
> > currently in the middle of reworking our interrupt management (and
> > interrupt numbers allocation layer) and Michael Ellermann is looking at
> > the MSI issue in parallel.
> 
> Just one point about MSI(-X) message address and data format. I think
> it should be the platform that defines the content.

That's an obvious requirement :)

> Current
> implementation doesn't have this flexibility. We have a design where
> MSI mode uses message data to carry vector number info while MSI-X
> mode uses message address to carry this info. Although it seems
> strange, but I think it's allowed by the spec.

The current implementation is bad :) There are some patches for altix
that are in -mm that add some platform hooks that make the situation a
little bit better, but it's still far from perfect.

Ben.