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

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Message-ID: <49F619C4.20100@freescale.com>
Date:	Mon, 27 Apr 2009 15:47:00 -0500
From:	Timur Tabi <timur@...escale.com>
To:	Ira Snyder <iws@...o.caltech.edu>
CC:	David Hawkins <dwh@...o.caltech.edu>,
	Liu Dave-R63238 <DaveLiu@...escale.com>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	Dan Williams <dan.j.williams@...el.com>,
	Kumar Gala <galak@...nel.crashing.org>
Subject: Re: [PATCH] fsldma: use PCI Read Multiple command

Adding Kumar to the CC: list, since he might pick up the patch.

Ira Snyder wrote:

> From 73e42fa58c93de8d4d429ba8e069b60c42037b58 Mon Sep 17 00:00:00 2001
> From: Ira W. Snyder <iws@...o.caltech.edu>
> Date: Thu, 23 Apr 2009 16:17:54 -0700
> Subject: [PATCH] fsldma: use PCI Read Multiple command
> 
> 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: Timur Tabi <timur@...escale.com>

-- 
Timur Tabi
Linux kernel developer at Freescale
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