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

[Dan Williams]

On 5/2/2011 7:21 PM, ååæ 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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