linux-kernel - Re: Dropped IRQ disables Radeon 3D

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Date:	Fri, 15 Jul 2011 19:09:44 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Michael Witten <mfwitten@...il.com>
Cc:	linux-kernel@...r.kernel.org, Arnuschky <arnuschky@...on.de>
Subject: Re: Dropped IRQ disables Radeon 3D

On Fri, 2011-07-15 at 08:20 +0000, Michael Witten wrote:
> 
> Arnuschky wrote to me about this related Debian bug report:
> 
>   Fri, 2010-06-18 10:21:05 +0000
>   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=586312
> 
> I popped over to #radeon on freenode where user agd5f told me to
> try the following on the kernel command line:
> 
>   pci=nomsi
> 
> After reading about MSIs and the requisite CONFIG_* settings, I
> realized that I didn't even have MSI support in the kernel anyway.
> Then agd5f suggested the following patches by Benjamin Herrenschmidt
> might be of help:

Another problem I noticed is some cards, when not using MSIs, still seem
to shoot an MSI with whatever value was last programmed into the MSI
configuration space. Can you check with lspci -vv if there's a non-0
value in there ? It -could- be that your get bogus MSIs.

Cheers,
Ben.

> 
> http://lists.freedesktop.org/archives/dri-devel/2011-July/012980.html
> 
> http://lists.freedesktop.org/archives/dri-devel/2011-July/012981.html
> 
> the latter of which fixes a syncronization bug on systems that use
> non-MSI IRQs (presumably pin-based IRQs) for the radeon device/driver.
> 
> For my system, I decided to enable MSI/MSI-X support by building
> Linux with the following configuration variables set:
> 
>   CONFIG_PCI=y
>   CONFIG_X86_LOCAL_APIC=y
>   CONFIG_X86_IO_APIC=y
>   CONFIG_PCI_MSI=y
> 
> and making sure I get the following:
> 
>   $ dmesg | grep MSI | grep radeon 
>   radeon 0000:01:00.0: irq 42 for MSI/MSI-X
>   radeon 0000:01:00.0: radeon: using MSI.
> 
> I'm not sure if this will avoid the problem, but it sure seems like
> a good bet.
> 
> 

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