linux-kernel - Re: [PATCH 02/20] ata_piix: unify code for programming PIO and MWDMA timings

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Message-ID: <4D62538C.1010200@ru.mvista.com>
Date:	Mon, 21 Feb 2011 14:59:08 +0300
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Sergei Shtylyov <sshtylyov@...sta.com>,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/20] ata_piix: unify code for programming PIO and MWDMA
 timings

Hello.

On 21-02-2011 14:58, Alan Cox wrote:

>>>>       PIO mode is setup by different code, and it takes care of the IORDY
>>>> setting according to the PIO rules (and it gets called). DMA mode setup should
>>>> just ignore the IORDY setting as in all other sane drivers.

>>> Well it can't ignore it - but if you mean just keep the bit as is then

>>      Yes, I mean this.

>>> that sounds sensible, have to see what the docs say happens if you ever
>>> set MWDMA without IORDY.

>>      Don't think they say anything on this matter but I can't imagine that
>> IORDY matters for DMA.

    ... unless the IE bit means something special (and undocumented) for DMA, 
if Intel so insists on setting it for every DMA mode.

> Sure - but it does matter for an ATAPI transaction with then has a DMA
> phase because those timings will be used for the command transfer which
> is PIO.

    So what? We've already setup PIO timings before the DMA ones. Why force 
the IE bit?

> Alan

WBR, Sergei
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