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Message-ID: <48977AE1.1070402@ru.mvista.com>
Date: Tue, 05 Aug 2008 01:55:45 +0400
From: Sergei Shtylyov <sshtylyov@...mvista.com>
To: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Robert Hancock <hancockr@...w.ca>,
Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
James Bottomley <James.Bottomley@...senpartnership.com>,
ksummit-2008-discuss@...ts.linux-foundation.org,
linux-kernel <linux-kernel@...r.kernel.org>,
linux-ide <linux-ide@...r.kernel.org>
Subject: Re: Kernel Summit request for Discussion of future of ATA (libata)
and IDE
Hello.
Alan Cox wrote:
>> I was looking into the 32-bit PIO issue a bit yesterday. It looks like
>> some of the VLB libata drivers are doing this internally already, so it
>> shouldn't be hard to do this in the core. Only question is how we know
>> generically if the controller can do it or not? It looks like in old
>>
>
> You don't. Basically it is controller dependant. Pretty much all the
> newer controllers support the 32bit PIO data cycles. Most PCI controllers
> it makes no speed difference but host bus controllers (especially
> PIIX/ICH) really benefit.
>
In what way if there's no speed gain?
>> supported. I couldn't track down where that bit was actually defined in
>> the first place, all the way back to ATA-1 it seems to be indicated as
>> reserved. Actually, I'm not sure why the drive cares in the first place,
>> it would seem like a pure host controller issue..
>>
>
> It goes back before IDE into the depths of the original compaq spec. When
> you have a device wired basically directly to the ISA bus (original IDE)
>
ISA has only 8/16-bit data bus, so it could not have mattered
there... and I don't think that there ever was a direct connection
between the IDE and host bus other than ISA... except maybe EISA.
MBR, Sergei
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