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961 Views
Registered: ‎03-03-2017

DisplayPort Rx link time to video flowing

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I am using a Kintex 7 325T device (using Vivado/SDK 2018.1) in a production environment where the FPGA sources HDMI video into our device under test (DUT) where the video flows through our DUT and ultimately comes back out of the DUT as DisplayPort video so I also have the FPGA receive the DP Video stream.   We are having trouble with the test time associated with linking the DisplayPort to the FPGA.   It seems the DP RX code I grabbed from an example design links, then waits for some fixed number of frames before allowing the video stream to begin flowing out into the AXI Stream video out of the DP Rx block.

I am wondering if anybody has had any success in updating the driver code to make the DisplayPort linking any faster?   Right now we are having to wait 5 to 6 seconds for the link, where in reality we should be able to get the video flowing in less than 100ms.

Any help will be greatly appreciated.

Thanks.

Tim

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757 Views
Registered: ‎03-03-2017

Re: DisplayPort Rx link time to video flowing

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I do notice I can speed it up by changing the expected vblank_count in the static void Dprx_InterruptHandlerVBlank interrupt handler.   Can somebody explain to me why I would not want to use a smaller number here?   Before I changed it to 20 it was set to 200.

 

dprx1.png

 

Thanks.

Tim

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913 Views
Registered: ‎03-03-2017

Re: DisplayPort Rx link time to video flowing

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If I use a Unigraf DPA-400 Auxiliary sniffer it appears that total linking time is only about 100ms, so I am wondering where the rest of the time is going in the driver code before it allows video to flow.

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Registered: ‎03-03-2017

Re: DisplayPort Rx link time to video flowing

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I do notice I can speed it up by changing the expected vblank_count in the static void Dprx_InterruptHandlerVBlank interrupt handler.   Can somebody explain to me why I would not want to use a smaller number here?   Before I changed it to 20 it was set to 200.

 

dprx1.png

 

Thanks.

Tim

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Scholar watari
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751 Views
Registered: ‎06-16-2013

Re: DisplayPort Rx link time to video flowing

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Hi @tim_severance

 

Do you need to consider compatibility ?

If no, I suggest what you do.

However, if yes, I strongly suggest keeping this code.

 

Best regards,

749 Views
Registered: ‎03-03-2017

Re: DisplayPort Rx link time to video flowing

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@watari,

   Thanks for the response.   When you say compatibility, do you mean that it should work with many different DisplayPort TX sources?   For me I only use a single DP Tx source so compatibility may not be an issue for me.

Thanks.

Tim

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Scholar watari
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746 Views
Registered: ‎06-16-2013

Re: DisplayPort Rx link time to video flowing

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Hi @tim_severance

 

How many PCBs do you build ?

How many DP Tx sources (include kind and number of DP Tx) do you consider ?

 

If this answer is very small number and/or a limited, I suggest your modified source code.

If other, because of this is an industrial product, at least I'm sure that you need to consider tolerant.

 

Of cause, if you consider the number of "vblankcounter" by cut-and-try, it's fine and I agree it.

 

Best regards,

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719 Views
Registered: ‎11-09-2015

Re: DisplayPort Rx link time to video flowing

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HI @tim_severance,

I would agree with @watari.

The code from the example design is the best we got to have a broader compatibility (based also on user feedback/corner cases). It is maybe not the most optimized code for some specific application but it is working.

I guess some part of the code are only "tweaks" which were only used in some cases so might be hard to explain. I am quite sure you can optimize the code for your specific application.

Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
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545 Views
Registered: ‎11-09-2015

Re: DisplayPort Rx link time to video flowing

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Hi @tim_severance,

What is your status on this topic? Was the replies enough for you?

If your question is answered or your issue is solved, please kindly mark the response which helped as solution (click on "Accept as solution" button below the reply)

If this is not solved/answered, please reply in the topic giving more information on your current status.

Thanks and Regards,


Florent
Product Application Engineer - Xilinx Technical Support EMEA
**~ Don't forget to reply, give kudos, and accept as solution.~**
532 Views
Registered: ‎03-03-2017

Re: DisplayPort Rx link time to video flowing

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@florentw,

   Sorry, the reduction works in my setup since in our production setup we only link DisplayPort to a single sink.   

Thanks. 

Tim