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Message-ID: <48979575.7090004@gmail.com>
Date: Tue, 05 Aug 2008 08:49:09 +0900
From: Tejun Heo <htejun@gmail.com>
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To: Jeff Garzik <jeff@garzik.org>
CC: Robert Hancock <hancockr@shaw.ca>,
       Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
       ksummit-2008-discuss@lists.linux-foundation.org,
       linux-kernel <linux-kernel@vger.kernel.org>,
       James Bottomley <James.Bottomley@hansenpartnership.com>,
       linux-ide <linux-ide@vger.kernel.org>,
       Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [Ksummit-2008-discuss] Kernel Summit request for Discussion of
 future of ATA (libata) and IDE
References: <fa.OGeO7gZvBG4obEzRbVltjSebgTQ@ifi.uio.no>	<fa.KtvYE2B2yrJqUleolhtMPN9ljAQ@ifi.uio.no>	<fa.AqEKTvguYFAzDFHy/We/8MpOqmo@ifi.uio.no>	<48976168.3020804@shaw.ca> <489768A1.8000501@garzik.org>
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Jeff Garzik wrote:
> Robert Hancock wrote:
>> Alan Cox wrote:
>>>> * There are still corner case in libata core - PIO is dead slow
>>>> compared to drivers/ide/,
>>> There are two there - libata keeps IRQs blocked for longer in PIO mode as
>>> well which is a factor for realtime that needs looking at, as well as
>>> using 16bit not 32bit I/O for most devices (which is trivial to fix). The
>>> IRQ masking stuff is more complex and old IDE handles it far better for
>>> PIO on non shared IRQ interfaces. That is actually probably the most
>>> complicated thing to address of the stuff you'd want to do if you were
>>> going to kill off old IDE.
>> 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 
>> IDE, a few controllers explicitly disable it, but it appears that it 
>> doesn't default to on for any controller, so it's possible there are 
>> others on which it doesn't work. Presumably anything on an actual 16-bit 
>> bus (ISA, LPC, etc.) wouldn't like it, to start with.
> 
> FWIW there is already a patch from Willy Terreau (sp?) to add 32-bit I/O.
> 
> I queued it for "later" because it had some issues that Alan pointed 
> out, IIRC.  I definitely want to push it in, though.

Jeff, have your thoughts about PIO IRQ disable handling changed yet?  I
don't really see any better way than doing it like IDE.

Thanks.

-- 
tejun
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