Write to host DDR on EC2 F1 Instance

Question

Is there any utility in the aws-fpga github repository that helps transfering data to host DDR memory?
I would like to use a DMA in the FPGA to transfer data directly to the host using the "S_AXI_PCIM" interface instead of writing the data to the FPGA DDR memory and then read that data from the host. 
![Enter image description here](/media/postImages/original/IMQvuNvTErS2qp64clYFkHIA)

I'm wondering if there is any utility provided that helps with this or I must develop a linux driver from scratch in order to get the physical address in host DDR where the FPGA DMA can write to.

Thanks in advance.
Ismael.

Answer

Hi Ismael,

Could you share some more information on the design you're planning to implement? Do you plan to implement a DMA for the Host -> FPGA over PCIS as well as a DMA for FPGA -> Host over PCIM?

Thanks!

-Joe

Answer

Hello,

Thank you for reaching out to AWS with your question. The S_AXI_PCIM interface provides a way for the Customer Design to initiate PCIe transaction cycles to the Host memory. The interface supports full AXI4 protocol with 512-bit wide datapath. Customers can easily interface their kernel, custom DMA, Xilinx IP with AXI4, etc, to S_AXI_PCIM interface to reach Host Memory.

AWS provides [Streaming Data Mover](https://github.com/aws/aws-fpga/blob/master/hdk/cl/examples/cl_sde/design/sde.sv), a custom Data Mover with AXI4-to-AXIS conversion to move data between FPGA and Host. Important links regarding SDE below:

[SDE IP Guide](https://github.com/aws/aws-fpga/blob/master/sdk/apps/virtual-ethernet/doc/SDE_HW_Guide.md#sde-hardware-guide)

[Example CL design using SDE IP](https://github.com/aws/aws-fpga/tree/master/hdk/cl/examples/cl_sde#cl_sde-custom-logic-example)

Please note, while the S_AXI_PCIM and above SDE IPs allow customer design to access host memory directly, they require Physical Memory Address of the Host and not the virtual memory address. Please refer to your Operating System details for Virtual-to-Physical Memory Address Translation.

Please let us know if you have any questions.

Thanks!

Chakra

Write to host DDR on EC2 F1 Instance

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