Message-ID: <477BDEA5.8040701@garzik.org>
Date: Wed, 02 Jan 2008 13:57:41 -0500
From: Jeff Garzik <jeff@garzik.org>
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To: Allen Martin <AMartin@nvidia.com>
CC: Robert Hancock <hancockr@shaw.ca>, Tejun Heo <htejun@gmail.com>,
       Gabor Gombas <gombasg@sztaki.hu>, linux-kernel@vger.kernel.org,
       linux-ide@vger.kernel.org, Kuan Luo <kluo@nvidia.com>,
       Peer Chen <pchen@nvidia.com>
Subject: Re: sata_nv + ADMA + Samsung disk problem
References: <20070808120804.GB5257@boogie.lpds.sztaki.hu> <20080101164416.GA29574@boogie.lpds.sztaki.hu> <477B0429.7040909@gmail.com> <477B0CFD.1030603@shaw.ca> <F72FA20C31DD4F4C997B91C5B3690A09505577@hqemmail07.nvidia.com>
In-Reply-To: <F72FA20C31DD4F4C997B91C5B3690A09505577@hqemmail07.nvidia.com>
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Allen Martin wrote:
>> The question I had for NVIDIA regarding this that I never got 
>> answered 
>> was, is there any reason why we would need a delay when switching 
>> between NCQ and non-NCQ commands on ADMA, and if not, is 
>> there any known 
>> cause that could cause the controller to get into this seemingly 
>> locked-up state?
> 
> When switching from NCQ to non NCQ or vice versa you must make sure all
> outstanding commands are completed before issuing the new command.  The
> hardware doesn't do anything to prevent queued and non queued commands
> from going out on the wire at the same time which will certainly cause
> some drives to fail.

The software definitely provides that guarantee for all NCQ-capable 
controllers.

	Jeff


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