linux-kernel - Re: [PATCH] PCI quirks: RS780/RS880: work around missing MSI initialization

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Message-ID: <20100322093205.5edc3f6a@jbarnes-piketon>
Date:	Mon, 22 Mar 2010 09:32:05 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Alex Deucher <alexdeucher@...il.com>
Cc:	Clemens Ladisch <clemens@...isch.de>, linux-pci@...r.kernel.org,
	dri-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI quirks: RS780/RS880: work around missing MSI 
 initialization

On Mon, 22 Mar 2010 12:28:00 -0400
Alex Deucher <alexdeucher@...il.com> wrote:

> On Mon, Mar 22, 2010 at 4:52 AM, Clemens Ladisch <clemens@...isch.de> wrote:
> > AMD says in section 2.5.4 (GFX MSI Enable) of #43291 (AMD 780G Family
> > Register Programming Requirements):
> >
> >  The SBIOS must enable internal graphics MSI capability in GCCFG by
> >  setting the following: NBCFG.NB_CNTL.STRAP_MSI_ENABLE='1'
> >
> > Quite a few BIOS writers misinterpret this sentence and think that
> > enabling MSI is an optional feature.  However, clearing that bit just
> > prevents delivery of MSI messages but does not remove the MSI PCI
> > capabilities registers, and so leaves these devices unusable for any
> > driver that attempts to use MSI.
> >
> > Setting that bit is not possible after the BIOS has locked down the
> > configuration registers, so we have to manually disable MSI for the
> > affected devices.
> >
> > This fixes the codec communication errors in the HDA driver when
> > accessing the HDMI audio device, and allows us to get rid of the
> > overcautious quirk in radeon_irq_kms.c.
> 
> Looks good.  This works properly on my rs780.
> 
> Tested-by: Alex Deucher <alexdeucher@...il.com>

Great, applied to my for-linus branch.  I'll send it over to Linus this
week.

-- 
Jesse Barnes, Intel Open Source Technology Center
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