From: Robert Hancock <hancockrwd@gmail.com>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Krzysztof Halasa <khc@pm.waw.pl>,
Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>,
linux-ide@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>
Subject: Re: SATA_SIL on IXP425 workaround
Date: Fri, 15 Jan 2010 23:03:27 -0600 [thread overview]
Message-ID: <4B51489F.8010105@gmail.com> (raw)
In-Reply-To: <20100114210515.7a477a43@lxorguk.ukuu.org.uk>
On 01/14/2010 03:05 PM, Alan Cox wrote:
>> We need to use the MMIO BAR at least for starting DMA transfers, the
>> I/O ones are 64KB-limited. We can't just use read[bw] if reading all
>> 32 bits has side effects.
>
> Last time I instrumented this on x86 we never issued a> 64K linear block
> in our s/g lists. In fact we went for years before anyone noticed we had
> a bug with CS5530 and a couple of other chips that mishandled 64K segment
> sizes, and that was only finally noticed in a very specific and weird
> circumstance.
Having a block over 64KB may be rare, but the other thing that the large
block transfer feature does is remove the restriction on a block
crossing a 64KB boundary, which based on the experiments I did when I
worked on adding the feature, does happen fairly commonly if the driver
allows it.
next prev parent reply other threads:[~2010-01-16 5:03 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-09 17:31 SATA_SIL on IXP425 workaround Krzysztof Halasa
2010-01-14 15:59 ` Bartlomiej Zolnierkiewicz
2010-01-14 18:08 ` Krzysztof Halasa
2010-01-14 19:22 ` Alan Cox
2010-01-14 20:12 ` Krzysztof Halasa
2010-01-14 21:05 ` Alan Cox
2010-01-16 5:03 ` Robert Hancock [this message]
2010-01-14 20:29 ` Bartlomiej Zolnierkiewicz
2010-01-14 21:00 ` Alan Cox
2010-01-21 5:00 ` Jeff Garzik
2010-01-21 4:58 ` Jeff Garzik
2010-01-21 6:48 ` Jeff Garzik
2010-01-21 18:37 ` Jeff Garzik
2010-01-21 21:47 ` Krzysztof Halasa
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