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

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Message-ID: <4DC027CA.5000606@intel.com>
Date:	Tue, 03 May 2011 09:05:30 -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 7:21 PM, 康剑斌 wrote:
>
>>> I try to use ioatdam to copy data from system memory to pci MMIO space:
>>> If dst points to a memory space, the operation would pass.
>>> But if dst points to a pci MMIO space, it failed with kernel oops.
>>> It seems the code:
>>> BUG_ON(is_ioat_bug(chanerr));
>>> in drivers/dma/ioat/dma_v3.c, line 365 cause the oops.
>>> Is there anyway to access pci MMIO space using ioat?
>>> The datasheet says that ioat supports MMIO access.
>> Did you map the IO memory in kernel using ioremap and friends first?
>>
> 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.
>

ioremap maps mmio space for the cpu not bus mastering devices.  You need 
to program the physical address into the descriptor.

--
Dan
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