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Observer naarayananrao
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Registered: ‎12-04-2019

Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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Hello 

How does one write the descriptors to the H2C and C2H channels in the bypass mode. I have enabled the channel bypass interfaces in Vivado, but not able to find how and where to write the descriptors from the PL side. Any help would be great!

Regards

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Observer naarayananrao
Observer
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Registered: ‎12-04-2019

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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I figured out a way to get the descriptor bypass mode working. I found the descriptor bypass ports in the design.vhd file and edited using an external editor and changed the source and destination address, control and length and generated the bitstream. Writing to the appropriate registers in SDK worked perfectly for me.

 

 

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Xilinx Employee
Xilinx Employee
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Registered: ‎10-09-2019

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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The Descriptor Bypass is explained in PG195 on page 26.

Please check the descriptor is being sent on the correct bus (c2h_dsc_byp / h2c_dsc_byp) and all control register bits are set correctly.

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Observer naarayananrao
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Registered: ‎12-04-2019

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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Hello @mmcnicho 

Thank you for the reply. I have read through the documentation. I am not able to understand how to send descriptors to the channels. Currently, I am using Stream FIFO to write to the channels. Is that alright or do you any other suggestions. Are the channels memory mapped so that I can write to their registers using the offsets given in the documentation?

Regards

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Moderator
Moderator
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Registered: ‎05-02-2017

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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hi @naarayananrao ,

 

Thanks for contacting xilinx  forums ,

Isee your looking for sample code , you generate the example design with the AXI4-Memory Mapped with Descriptor Bypass Example in vivado.

When Descriptor bypass mode is enabled, the user logic is responsible for making descriptors and transferring them in descriptor bypass interface. Mapped design with descriptor bypass mode enabled. You can select which channels will have
descriptor bypass mode. When Channel 0 of H2C and Channel 0 C2H are selected for Descriptorbypass mode, the generated Vivado example design has descriptor bypass ports of H2C0 andC2H0 connected to logic that will generate only one descriptor of 64bytes. The user is responsible for developing codes for other channels and expanding the descriptor itself.

 

Let me know your inputs

 

chandra 

Regards
Chandra sekhar
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Observer naarayananrao
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Registered: ‎12-04-2019

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

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Thank you @csattar 

I have enabled the channel 0 of H2C as I need only H2C transfer. I have enabled and configured everything what the descriptor bypass example design suggests. My question is how to pass the 64 byte descriptor? Should I do it from the SDK or from Vivado? Should I use any IP blocks to do that or should I just write to it?

If yes, then what is the base address and offset address for these channels and what is the procedure to send the descriptors. Can you please explain in detail.

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Observer naarayananrao
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Registered: ‎12-04-2019

Re: Writing Descriptors to the channels in Descriptor Bypass mode - XDMA

Jump to solution

I figured out a way to get the descriptor bypass mode working. I found the descriptor bypass ports in the design.vhd file and edited using an external editor and changed the source and destination address, control and length and generated the bitstream. Writing to the appropriate registers in SDK worked perfectly for me.

 

 

View solution in original post

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