IIO for PCIe-DMA ADC

IIO for PCIe-DMA ADC

[Krzysztof Sywula]

Hi there, I’m designing a PCIe driver for DMA enabled ADC. Is IIO handling
such a combo? I'm based on kernel 3.8.7.

Website:
http://wiki.analog.com/software/linux/docs/iio/iio
says "However typical DMA operated devices such as ones connected to a
high speed synchronous serial (McBSP, SPORT) or high speed synchronous
parallel (EPI, PPI) or FPGA peripherals are also subject to this
subsystem."

which is not clear enough for me to answer that question.

Thanks,
Krzysztof Sywula

Re: IIO for PCIe-DMA ADC

[Lars-Peter Clausen]

On 07/24/2014 03:06 PM, Krzysztof Sywula wrote:
> Hi there, I’m designing a PCIe driver for DMA enabled ADC. Is IIO handling
> such a combo? I'm based on kernel 3.8.7.
>
> Website:
> http://wiki.analog.com/software/linux/docs/iio/iio
> says "However typical DMA operated devices such as ones connected to a
> high speed synchronous serial (McBSP, SPORT) or high speed synchronous
> parallel (EPI, PPI) or FPGA peripherals are also subject to this
> subsystem."
>
> which is not clear enough for me to answer that question.


Hi,

The current upstream version of IIO does not have built-in support for DMA, 
but you can always create your custom buffer implementation that handles the 
DMA.

There is a out of tree generic DMA[0] and DMAengine[1] support for IIO. This 
is both scheduled for mainline submission, but obviously will not be 
available in a 3.8.7 kernel.

- Lars

[0] 
https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmabuf.c
[1] 
https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmaengine.c

Re: IIO for PCIe-DMA ADC

[Krzysztof Sywula]

Lars, I have few more questions, would love if you could answer.
- ADC I have uses max 4KHz sampling frequency, SoC CPU is 533MHz; will IIO
cope?
- are there any other ADCs in IIO framework that use your DMA-extension?
- I would like to use dw_dmac DMA driver, I hope both, IIO and your
DMA-extension will honour that
- what is the status of upstreaming DMA-extension? Are you commited to any
dates?
- is there any out of the box set of tests for IIO/DMA-extension?

Thanks,
Krzysztof Sywula

> On 07/24/2014 03:06 PM, Krzysztof Sywula wrote:
>> Hi there, I’m designing a PCIe driver for DMA enabled ADC. Is IIO
>> handling
>> such a combo? I'm based on kernel 3.8.7.
>>
>> Website:
>> http://wiki.analog.com/software/linux/docs/iio/iio
>> says "However typical DMA operated devices such as ones connected to a
>> high speed synchronous serial (McBSP, SPORT) or high speed synchronous
>> parallel (EPI, PPI) or FPGA peripherals are also subject to this
>> subsystem."
>>
>> which is not clear enough for me to answer that question.
>
>
> Hi,
>
> The current upstream version of IIO does not have built-in support for
> DMA,
> but you can always create your custom buffer implementation that handles
> the
> DMA.
>
> There is a out of tree generic DMA[0] and DMAengine[1] support for IIO.
> This
> is both scheduled for mainline submission, but obviously will not be
> available in a 3.8.7 kernel.
>
> - Lars
>
> [0]
> https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmabuf.c
> [1]
> https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmaengine.c
>
>

Re: IIO for PCIe-DMA ADC

[Lars-Peter Clausen]

On 07/28/2014 01:09 PM, Krzysztof Sywula wrote:
> Lars, I have few more questions, would love if you could answer.
> - ADC I have uses max 4KHz sampling frequency, SoC CPU is 533MHz; will IIO
> cope?

That's more of a hardware issue and less of a IIO framework issue. But I 
think 4kHz is something that's even without DMA possible to archive without 
problems.

> - are there any other ADCs in IIO framework that use your DMA-extension?

Not at this point.

> - I would like to use dw_dmac DMA driver, I hope both, IIO and your
> DMA-extension will honour that

If the dw_dmac driver is compliant with the DMAengine API it will work out 
of the box.

> - what is the status of upstreaming DMA-extension? Are you commited to any
> dates?

soon ;) The plan is to at least send the kernel parts after the next merge 
window has closed.

> - is there any out of the box set of tests for IIO/DMA-extension?

The userspace API is backwards compatible so you can use the same tools that 
can be used to test other IIO applications.

- Lars

>
> Thanks,
> Krzysztof Sywula
>
>> On 07/24/2014 03:06 PM, Krzysztof Sywula wrote:
>>> Hi there, I’m designing a PCIe driver for DMA enabled ADC. Is IIO
>>> handling
>>> such a combo? I'm based on kernel 3.8.7.
>>>
>>> Website:
>>> http://wiki.analog.com/software/linux/docs/iio/iio
>>> says "However typical DMA operated devices such as ones connected to a
>>> high speed synchronous serial (McBSP, SPORT) or high speed synchronous
>>> parallel (EPI, PPI) or FPGA peripherals are also subject to this
>>> subsystem."
>>>
>>> which is not clear enough for me to answer that question.
>>
>>
>> Hi,
>>
>> The current upstream version of IIO does not have built-in support for
>> DMA,
>> but you can always create your custom buffer implementation that handles
>> the
>> DMA.
>>
>> There is a out of tree generic DMA[0] and DMAengine[1] support for IIO.
>> This
>> is both scheduled for mainline submission, but obviously will not be
>> available in a 3.8.7 kernel.
>>
>> - Lars
>>
>> [0]
>> https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmabuf.c
>> [1]
>> https://github.com/analogdevicesinc/linux/blob/xcomm_zynq/drivers/iio/industrialio-dmaengine.c
>>
>>
>
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