Date: Mon, 5 Nov 2007 13:03:30 +0000
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Tejun Heo <htejun@gmail.com>
Cc: albertl@mail.com, albertcc@tw.ibm.com, Daniel Drake <dsd@gentoo.org>,
       Jeff Garzik <jeff@garzik.org>, Jens Axboe <jens.axboe@oracle.com>,
       linux list <linux-kernel@vger.kernel.org>, linux-ide@vger.kernel.org
Subject: Re: "Fix ATAPI transfer lengths" causes CD writing regression
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On Mon, 05 Nov 2007 09:05:48 +0900
Tejun Heo <htejun@gmail.com> wrote:

> Alan Cox wrote:
> >> Maybe we could set a limit here. If the ATAPI device keeps DRQ=1 and
> >> exceeds the limit, we consider it as HSM violation and have EH handle it.
> > 
> > On a DMA transfer its basically out of our control (and a PIO drain will
> > lock some controllers solid until power cycle),
> 
> Do such controllers lock up on PIO draining after PIO transfers too?
> Can you tell which are those controllers?

Promise PDC202xx will lock on a PIO drain of a DMA transfer or (if you
reset it before you drain) on a PIO drain of a PIO transfer.

> > but on PIO we know we
> > never set a chunk size over 64K, so if we exceed 64K its time to apply a
> > larger hammer
> 
> Draining is related to the amount of data the drive responds not to the
> chunk size.  I agree 64k should be enough for most cases but I think
> there can be corner cases where this doesn't hold.

Tapes perhaps yes ?
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