linux-kernel - Re: [PATCH] ALSA: hda-intel - Disable MSI support by default

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Date:	Wed, 15 Nov 2006 11:09:53 -0800
From:	Stephen Hemminger <shemminger@...l.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ALSA: hda-intel - Disable MSI support by default

On Tue, 14 Nov 2006 23:24:04 -0500
Jeff Garzik <jeff@...zik.org> wrote:

> David Miller wrote:
> > Is this absolutely true?  I've never been sure about this point, and I
> > was rather convinced after reading various documents that once you
> > program up the MSI registers to start generating MSI this implicitly
> > disabled INTX and this was even in the PCI specification.
> > 
> > It would be great to get a definitive answer on this.
> > 
> > If it is mandatory, perhaps the driver shouldn't be doing it and
> > rather the PCI layer MSI enabling should.

pci_enable_msi() calls msi_capability_init() and that disables intx
already.


> 
> I can't answer for the spec, but at least two independent device vendors 
> recommended to write an MSI driver that way (disable intx, enable msi).
> 
> Completely independent of MSI though, a PCI 2.2 compliant driver should 
> be nice and disable intx on exit, just to avoid any potential interrupt 
> hassles after driver unload.  And of course be aware that it might need 
> to enable intx upon entry.
> 
> 	Jeff

The driver shouldn't deal with this, pci_disable_msi() does.

-- 
Stephen Hemminger <shemminger@...l.org>
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