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

[Dan Williams <dan.j.williams@intel.com>]

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