linux-kernel - Re: [PATCH] fsldma: use PCI Read Multiple command

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Date:	Mon, 27 Apr 2009 15:48:21 +0800
From:	Li Yang <leoli@...escale.com>
To:	Ira Snyder <iws@...o.caltech.edu>
Cc:	linux-kernel@...r.kernel.org,
	Dan Williams <dan.j.williams@...el.com>,
	linuxppc-dev@...abs.org
Subject: Re: [PATCH] fsldma: use PCI Read Multiple command

On Sat, Apr 25, 2009 at 2:35 AM, Ira Snyder <iws@...o.caltech.edu> wrote:
> By default, the Freescale 83xx DMA controller uses the PCI Read Line
> command when reading data over the PCI bus. Setting the controller to use
> the PCI Read Multiple command instead allows the controller to read much
> larger bursts of data, which provides a drastic speed increase.
>
> The slowdown due to using PCI Read Line was only observed when a PCI-to-PCI
> bridge was between the devices trying to communicate.
>
> A simple test driver showed an increase from 4MB/sec to 116MB/sec when
> performing DMA over the PCI bus. Using DMA to transfer between blocks of
> local SDRAM showed no change in performance with this patch. The dmatest
> driver was also used to verify the correctness of the transfers, and showed
> no errors.
>
> Signed-off-by: Ira W. Snyder <iws@...o.caltech.edu>

Acked-by: Li Yang <leoli@...escale.com>

Thanks,
Leo
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