IPU DMA Raw Memory Transfer on i.MX6

[jrios]

Hello,

I need to perform a raw memory copy using IPU DMA and without modifying the data. I am using IPU because I need the DMA to PCIe space.

How do I use an IPU processing sub-block which falls-through and does a 1:1 transfer of data to and from a buffer in ram?

Best Regards,

Jose

[JayTu]

I don't think IPU DMA can be used that way. Doesn't PCIe have DMA channel?

[jrios]

Hello JayTu,

According to the i.MX6DQ reference manual and discussions with Freescale support, the i.MX6 PCIe core does not have a DMA channel.

On the other hand, I have seen an example for using IPU DMA Bus master for PCIe transactions here: https://community.freescale.com/docs/DOC-95014

My application requires DMA support to achieve the necessary transfer rates. The standard PCIe RC, non-DMA, transfers are too slow for my application and the operations are split into multiple TLP's.

Unfortunately, I have been unable to properly configure the IPU channel to achieve a one-to-one memory transfer operation from system RAM to PCIe EP space using IPU DMA. The data is modified when it is transferred across the IPU channel.

I suspect this is due to IPU configuration settings (rotation, scaling, etc).

I look forward to any input anyone has on this topic.

Best regards,

Jose Rios

[yanntinaugus]

Dear M Rios,

I am actually stuck to the same problem than you. I have to perform DMA through PCI and I arrive to the same conclusion : PCIe does not have DMA channel.

I then have to use the IPU DMA (which is IDMAC) to do the transaction. But I don't really have idea about how to do it. So my questions are :

1) Did you finally manage to find a solution to your problem ?

2) Could you help me, and give me some tips about how to do it ? I mean that you give me highlight of how to do it ?

Thanks in advance for your help,

Best regards,

Yann Tinaugus

[wooosaiiii]

Did you manage to implement IPU DMA transfers to PCIe address space without modification, eg 1:1 mapping?