Re: [patch 2/2] sata_via: Delay on vt6420 when starting ATAPI DMA write

From: Bart Hartgers
Date: Wed Jan 20 2010 - 01:33:34 EST


2010/1/20 Robert Hancock <hancockrwd@xxxxxxxxx>:
> On 01/19/2010 09:30 PM, Tejun Heo wrote:
>> Hello,
>> On 01/17/2010 08:56 AM, Bart Hartgers wrote:
>>> When writing a disc on certain lite-on dvd-writers (also rebadged as
>>> optiarc/LG/...) connected to a vt6420, the ATAPI CDB ends up in the
>>> datastream and on the disc, causing silent corruption. ÂDelaying
>>> between sending the CDB and starting DMA seems to prevent this.
>>> I do not know if there are burners that do not suffer from this, but
>>> the patch should be safe for those as well.
>>> There are many reports of this issue, but AFAICT no solution was
>>> found before. For example:
>>> Signed-off-by: Bart Hartgers<bart.hartgers@xxxxxxxxx>
>> Ah... you found solution for this? ÂThat's great. ÂThis is one of the
>> three problems that have been lingering for years - the other two
>> being pata_ali ATAPI DMA problem and sata_sil data corruption problem.
>> I'll be ecstatic if this fix works. ÂJust one thing, I don't think
>> we'll need a warning message there. ÂIt's useful during development
>> but it doesn't really provide any useful information afterwards.
> Another tiny nitpick about the patch, the unlikely() around the
> DMA_TO_DEVICE check probably shouldn't be there - unlikely() is for things
> that will always be either highly unlikely or a slow path, neither of which
> really apply.

Well, the ata_sff_pause actually does a ndelay(400), and with today's
processors that would be a 'slow path', right?


>> Digging up the mailing list and cc'ing people who have reported this
>> problem. ÂIf you still have the affected systems, can you guys please
>> test the patch in the following message and see whether it fixes the
>> problem?
>> Â
>> Thanks a lot. Â:-)

Bart Hartgers - New e-mail: bart.hartgers@xxxxxxxxx
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