linux-kernel - Re: [PATCH] Disable Bus Master on PCI device shutdown

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Message-ID: <m21ulrjbji.fsf@firstfloor.org>
Date:	Thu, 07 Jun 2012 10:07:29 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Matthew Garrett <mjg@...hat.com>, Khalid Aziz <khalid.aziz@...com>,
	linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] Disable Bus Master on PCI device shutdown

Alan Cox <alan@...rguk.ukuu.org.uk> writes:

>> This protects against the case where a piece of hardware is continuing 
>> to DMA even after the driver shutdown method has been called? I'm not 
>
> It doesn't. We also have hardware which craps itself if you clear the bus
> mastering bit and we have platforms where the BIOS gets most upset if you
> do that on suspend paths. There are also lots of devices that simply
> ignore the bus mastering bit !

But it also makes my system do kexec successfully for the first time.

Maybe can make it an option.

n-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only
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