Re: Mem-2-Mem DMA - Generalized API

From: Matt Sealey <matt@genesi-usa•com>
To: Arnd Bergmann <arnd@arndb•de>
Cc: linuxppc-embedded@ozlabs•org
Subject: Re: Mem-2-Mem DMA - Generalized API
Date: Mon, 25 Jun 2007 12:03:06 +0100	[thread overview]
Message-ID: <467FA0EA.3000607@genesi-usa.com> (raw)
In-Reply-To: <200706242221.57507.arnd@arndb.de>

IOAT and Intel's DMA engine driver is very IOAT specific in places..

I had a peek at it as I have a little interest in the concept; at least the
two platforms Genesi has been supporting (Pegasos and Efika) have quite
competant DMA engines which are woefully underused (i.e. not at all).

There exists a Marvell DMA driver somewhere (I have a copy, someone on
this list posted it about a year ago) and while the MPC5200B doesn't have
explicit support for DMA from memory to memory (although memory to SRAM
might work in chunks, or memory to a FIFO wired as a loopback like in
the docs..??)

There is so much you can do with most SoC DMA controllers, and it's not
even limited to PowerPC (most ARM/XScale SoCs have very capable devices
inside too). I can only imagine that nobody got excited over IOAT because
the entire programming interface stinks of "offloading gigabit ethernet"
and not much else.

-- 
Matt Sealey <matt@genesi-usa•com>
Genesi, Manager, Developer Relations

Arnd Bergmann wrote:
> On Sunday 24 June 2007, Clifford Wolf wrote:
>> I'm working on an MPC8349E based project and as some of you might know this
>> chip has a four channel (bus-) memory-to-memory DMA controller.
>>
>> Unfortunately the linux kernel is atm lacking a generic interface for such
>> DMA controllers.
> 
> So what's wrong with the include/linux/dmaengine.h API? I thought it was
> designed to cover this sort of DMA controller?
> 
> 	Arnd <><
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