linux-kernel - Re: Can I/OAT DMA engineer access PCI MMIO space

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Date:	Tue, 03 May 2011 08:58:26 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	康剑斌 <kjbmail@...il.com>
CC:	"Koul, Vinod" <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Can I/OAT DMA engineer access PCI MMIO space

On 5/2/2011 11:31 PM, 康剑斌 wrote:
>
>>> yes, I had used 'ioremap_nocache' to map the IO memory and I can use
>>> memcpy to copy data to this region. The async_tx should have been
>>> correctly configured as
>>> I can use aync_memcpy to copy data between different system memory address.
>> Then you should be using memcpy_toio() and friends
>>
> Do you mean that if I have mapped the mmio, I can' use I/OAT dma
> transfer to this region any more?
> I can use memcpy to copy data, but it consumes lots of cpu as PCI access
> is too slow.
> If I can use i/oat dma and asyc_tx api to do the job, the performance
> should be imporved.
> Thanks

The async_tx api only supports memory-to-memory transfers.  To write to 
mmio space with ioatdma you would need a custom method, like the 
dma-slave support in other drivers, to program the descriptors with the 
physical mmio bus address.

--
Dan
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