iMX8M Plus PCIe DMA Feature

[waynechung2]

Hello NXP,

According to the document "AN13164 iMX8MP PCIe Bandwith Analysis", it have the Linux PCI test and test by DMA.
The document "IMX8MPRM- i.MX 8M Plus Applications Processor Reference Manual - Document Number: IMX8MPRM Rev. 1, 06/2021" also show the "Embedded DMA" feature.

Could I write/read PCIe data by DMA ?

Thanks.

Best Regards,

Wayne.

[Zhiming_Liu]

Yes, you can use DMA in PCIe

[dwang2]

Hi NXP TechSupport,

The URL pointing to the sample code in the original email trail does not work. Could you post a working one?

I am looking for a working kernel module code that fetches data on a remote device over PCIe bus by using the SDMA. Any related sample code using the Linux kernel PCIe stack and the DMAEngine are very helpful.

Thanks you very much!

dwang2

[waynechung2]

Hello NXP,

How could I use the PCIe DMA ?

Could you provide any reference code or document ?

Thanks.

Best Regards,

Wayne.

[pete_sensoray]

Hi Wayne,

The documentation is IMX8MPRM.pdf section 11.4.2.4 DMA Controller.

The reference code is here: https://source.codeaurora.org/external/imx/linux-imx/tree/drivers/pci/controller/dwc/pci-imx6.c?h=im...

Look for the function "imx6_pcie_local_dma_start".  That code seems to have been removed from the latest kernel release, but I was able to add it back in and it seems to work.  But it doesn't seem to be part of the pci_endpoint_test, so I'm unable to recreate the bandwidth results from AN13164 since NXP didn't describe how to run the benchmark.