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

From: Bart Hartgers <bart.hartgers@gmail.com>
To: Robert Hancock <hancockrwd@gmail.com>
Cc: Tejun Heo <htejun@gmail.com>,
	linux-kernel@vger.kernel.org, Jeff Garzik <jgarzik@pobox.com>,
	linux-ide@vger.kernel.org, juergen.metzdorf@telelev-dsl.de,
	markpschool@hotmail.com, sporadic.crash@gmail.com,
	apopov@sirma.bg, david@coomber.co.za, jay4mail@gmail.com
Subject: Re: [patch 2/2] sata_via: Delay on vt6420 when starting ATAPI DMA write
Date: Wed, 20 Jan 2010 07:33:24 +0100	[thread overview]
Message-ID: <7eb6a4d81001192233i5418249ct5a1717045f75167c@mail.gmail.com> (raw)
In-Reply-To: <4B568C63.4050506@gmail.com>

Hi,

2010/1/20 Robert Hancock <hancockrwd@gmail.com>:
> 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.  Delaying
>>> 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:
>>> http://lkml.indiana.edu/hypermail/linux/kernel/0802.3/0561.html
>>>
>>> Signed-off-by: Bart Hartgers<bart.hartgers@gmail.com>
>>
>> Ah... you found solution for this?  That's great.  This 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.  Just one thing, I don't think
>> we'll need a warning message there.  It'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?

Groeten,
Bart

>>
>> Digging up the mailing list and cc'ing people who have reported this
>> problem.  If you still have the affected systems, can you guys please
>> test the patch in the following message and see whether it fixes the
>> problem?
>>
>>   http://article.gmane.org/gmane.linux.kernel/939112/raw
>>
>> Thanks a lot.  :-)
>>
>
>

-- 
Bart Hartgers - New e-mail: bart.hartgers@gmail.com