linux-kernel - Re: [PATCH 6/6] PCI MSI: Add support for multiple MSI

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Message-ID: <20090316210726.GO14127@parisc-linux.org>
Date:	Mon, 16 Mar 2009 15:07:26 -0600
From:	Matthew Wilcox <matthew@....cx>
To:	Michael Ellerman <michael@...erman.id.au>
Cc:	linux-pci@...r.kernel.org, jbarnes@...tuousgeek.org,
	linux-kernel@...r.kernel.org,
	Matthew Wilcox <willy@...ux.intel.com>
Subject: Re: [PATCH 6/6] PCI MSI: Add support for multiple MSI

On Tue, Mar 03, 2009 at 11:16:13AM +1100, Michael Ellerman wrote:
> > diff --git a/arch/powerpc/kernel/msi.c b/arch/powerpc/kernel/msi.c
> > index 3bb7d3d..0c16e2a 100644
> > --- a/arch/powerpc/kernel/msi.c
> > +++ b/arch/powerpc/kernel/msi.c
> > @@ -19,6 +19,10 @@ int arch_msi_check_device(struct pci_dev* dev, int nvec, int type)
> >  		return -ENOSYS;
> >  	}
> >  
> > +	/* PowerPC doesn't support multiple MSI yet */
> > +	if (type == PCI_CAP_ID_MSI && nvec > 1)
> > +		return 1;
> > +
> >  	if (ppc_md.msi_check_device) {
> >  		pr_debug("msi: Using platform check routine.\n");
> >  		return ppc_md.msi_check_device(dev, nvec, type);
> 
> That bit:
> 
> Acked-by: Michael Ellerman <michael@...erman.id.au>
> 
> I'll tell benh to expect this hunk to show up sometime via Jesse's tree.

Thanks!

> Looks good otherwise, not sure if we'll ever implement it, but good to
> have. Is AHCI the only driver you're planning on using it for ATM?

That's the only one I know where it's important.  I think some PCIe
bridges would like to have multiple MSI.  And I think some hardware
designs (not from Intel, from other companies who've talked to me) are
in the pipe to use multiple MSI, because it's cheaper than using MSI-X.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
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