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Date: Fri, 17 May 2002 12:12:55 +0200
From: Martin Dalecki <dalecki@evision-ventures.com>
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To: Neil Conway <nconway.list@ukaea.org.uk>
CC: Mike Fedyk <mfedyk@matchmail.com>, vda@port.imtp.ilyichevsk.odessa.ua,
        Anton Altaparmakov <aia21@cantab.net>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Russell King <rmk@arm.linux.org.uk>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] 2.5.15 IDE 61
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Uz.ytkownik Neil Conway napisa?:
> Mike Fedyk wrote:
> 
>>On Wed, May 15, 2002 at 12:55:37PM +0100, Neil Conway wrote:
>>
>>>You can (and must) safely "touch the cable" in between TCQ commands in
>>>the right circumstances.  You are therefore touching the cable while the
>>>hwgroup is busy, hence my suggestion that the flag we use to prevent
>>>touching the cable during DMA should be named something other than busy.
>>
>>Ahh, but with TCQ the concept of busy changes.  The wire (simplified) is
>>only busy when the tags are being transfered, otherwise the cable is unused
>>unless the cable has been "locked" by one of the devices.
> 
> 
> Hmm: "locked by one of the devices": do you mean a DMA transfer for
> example?  These are initiated by the host, but proceed asynchronously,
> so I'm not sure I'd describe it as being locked "by the device" as
> such.  At any rate, the IDE code has to remember that the cable is
> asynchronously active until DMA ends...  (Or I suppose it could just
> check the hwif BMDMA bits for the active state.)

Grep for IDE_DMA busy bits to see it - it does precisely this.