linux-kernel - Re: [patch 29/30] sata_nv: don't read shadow registers when in ADMA mode

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Date:	Fri, 09 Mar 2007 08:27:47 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	Jeff Garzik <jeff@...zik.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	akpm@...ux-foundation.org, linux-ide@...r.kernel.org
Subject: Re: [patch 29/30] sata_nv: don't read shadow registers when in ADMA
 mode

Jeff Garzik wrote:
> akpm@...ux-foundation.org wrote:
>> From: Robert Hancock <hancockr@...w.ca>
>>
>> Reading from the ATA shadow registers while we are in ADMA mode may cause
>> undefined behavior.  Don't read the ATA status register when completing
>> commands for this reason, it shouldn't be needed as the controller will
>> notify us if the command failed.  Also, don't allow commands with result
>> taskfile requested to execute in ADMA mode, since that requires accessing
>> the shadow registers.  We also still need to override tf_read since 
>> libata
>> will read the result taskfile on a command failure, and we need to go 
>> into
>> port register mode before allowing this.
>>
>> Signed-off-by: Robert Hancock <hancockr@...w.ca>
>> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>> ---
>>
>>  drivers/ata/sata_nv.c |   33 ++++++++++++++++++++-------------
>>  1 file changed, 20 insertions(+), 13 deletions(-)
> 
> Robert, do you think this should be pushed into #upstream-fixes 
> (2.6.21-rc)?
> 
> I lean towards "yes", since it is a needed-by-hardware fix, but I also 
> am interested in testing feedback since it is so late in the 2.6.21-rc 
> game.

I would lean toward that as well, but it would be good to get some 
testing from some sata_nv ADMA users to make sure it doesn't do anything 
funny for them..

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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