linux-kernel - Re: [patch] PCI: disable MSI on more ATI NorthBridges

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Message-ID: <471911BE.2000405@garzik.org>
Date:	Fri, 19 Oct 2007 16:21:18 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Linas Vepstas <linas@...tin.ibm.com>
CC:	Shane Huang <chunhao.huang@...mail.com>, davem@...emloft.net,
	gregkh@...e.de, htejun@...il.com, brice.goglin@...il.com,
	david.gaarenstroom@...il.com, linux-kernel@...r.kernel.org,
	linux-pci@...ey.karlin.mff.cuni.cz, shane.huang@....com,
	linux-ide@...r.kernel.org, Brice Goglin <brice@...i.com>
Subject: Re: [patch] PCI: disable MSI on more ATI NorthBridges

Linas Vepstas wrote:
> On Fri, Oct 19, 2007 at 09:17:23PM +0800, Shane Huang wrote:
>> Since we have little experience on PCI and MSI here, we had to try to
> 
> As someone else pointed out, AMD should have *lots* of people with
> pci and msi experience on the payroll.  (Folks here buy AMD-designed 
> pci chips ...)
> 
>> ONLY
>> comment out the pci_intx() call in drivers/ata/ahci.c
>> My system can boot up too with MSI enabled!
>>
>> So does it mean that the root cause is our SB700 SATA controller
>> has a hardware bug where setting INTX_DISABLE in the PCI COMMAND
>> register masks MSI interrupts too? 
> 
> That's what it sounds like, to me.
> 
>> And what is the software solution or workaround?
> 
> Not sure. Sounds like the device driver needs a quirk for this part.


Take a look at tg3.c net driver change 
2fbe43f6f631dd7ce19fb1499d6164a5bdb34568 which is a similar situation.

However, it may turn out that removing the pci_intx() stuff as a general 
rule is easier than quirking these devices, if enough of them turn out 
to have this hardware bug.

The tg3.c change should illustrate how to fix immediately, though.

	Jeff

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