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Message-ID: <477BDEA5.8040701@garzik.org>
Date: Wed, 02 Jan 2008 13:57:41 -0500
From: Jeff Garzik <jeff@...zik.org>
To: Allen Martin <AMartin@...dia.com>
CC: Robert Hancock <hancockr@...w.ca>, Tejun Heo <htejun@...il.com>,
Gabor Gombas <gombasg@...aki.hu>, linux-kernel@...r.kernel.org,
linux-ide@...r.kernel.org, Kuan Luo <kluo@...dia.com>,
Peer Chen <pchen@...dia.com>
Subject: Re: sata_nv + ADMA + Samsung disk problem
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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