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DZuck1's avatar
DZuck1
Icon for Occasional Contributor rankOccasional Contributor
6 years ago

DisplayPort Only Connects to Windows not Linux

Hi, I am trying to use the DisplayPort sample design on a Stratix 10 board. I have implemented the exact sample project from Intel with the Bitec daughter card but am seeing some issues. When I plu...
Deshi_Intel's avatar
Deshi_Intel
Icon for Regular Contributor rankRegular Contributor
6 years ago

Hi Daniel,

I presume your system setup is like below. Correct me if I am wrong

  • win/linux CPU -> DP Rx -> DP Tx -> monitor

Does connecting win CPU -> monitor directly (via DP cable) works ?

Do you have S10 GX dev kit board to try out to rule out potential board setup issue ?

Have you try different brand or shorter DP cable to check for potential signal integrity concern ?

Are you using below Stratix 10 Intel FPGA DisplayPort design example ?

I believe it's not about the OS difference issue but rather on the graphic card issue

  • I presume you are using different graphic card on Win and Linux machine ?
  • Have you compare the spec between these 2 graphic card to find out the difference that maybe the root cause
  • Have you try to play around with Nvidia graphic card setting to see if it helps ? (Like BPC setting, lower down video resolution, disable adaptive sync and etc)
  • Also do you really need HBR3 (8G datarate) for 4Kp60 resolution ? Can you try change DisplayPort IP to 4G datarate channel to see if works ?
  • If you are using DP example design, can you dump out the MSA log as per attached 4k support sample screenshot ?

Thanks.

Regards,

dlim

  • DZuck1's avatar
    DZuck1
    Icon for Occasional Contributor rankOccasional Contributor
    6 years ago
    Hi Dlim, I did not have access to the hardware today but will try to get the logs you are asking for tomorrow. As for the setup question. I am using a dual boot PC that boots both into Windows and Linux. The exact same graphics card, DisplayPort cable and Bitec RX port are being used for the test. The only variable here is the OS which is why I am confused why it doesn’t work. The hardware all works with Windows. I will also try to grab the AUX logs and send that to you if that is of any help. Thanks, Daniel
    • Deshi_Intel's avatar
      Deshi_Intel
      Icon for Regular Contributor rankRegular Contributor
      6 years ago

      Hi Daniel,

      Thanks for the clarification on dual OS boot using same graphic card. That means your hardware setup should be fine and no signal integrity concern.

      In this case, I don't think sending debug log to me will be any useful anymore. The most we can prove is graphic card is not sending correct data to DP Rx in Linux OS.

      • DP Rx is just a reception IP. DP Rx cannot control how DP Tx source (graphic card) transmit AUX data to DP Rx.
      • Something is funny happening on Linux OS.

      The direct relation that I can think of between graphic card interaction with OS would be graphic card driver.

      • The easiest way will be to either upgrade or downgrade Nvidia Linux OS driver installation and hope that it fix the issue
      • Or the other possibility is you configure different graphic card setting in Linux OS vs Win OS that somehow cause the failure. You may want to cross check the setting between 2 OS.
      • Finally if you had confirmed the graphic card setting used in both OS is the same but video output failure still happened. Then my suggestion is you can raise this issue back to Nvidia to seek their help in understanding graphic card driver difference between Win OS and Linux OS.

      Thanks.

      Regards,

      dlim

    • DZuck1's avatar
      DZuck1
      Icon for Occasional Contributor rankOccasional Contributor
      6 years ago
      Hi Dlim, I have tried two different NVIDIA graphics cards in Linux (two different drivers) and neither one seems to work with the DP IP core. I have signalTap on the output of the Bitec Clkrec core (Data, HSYNC, VSYNC & VID_DE) and they do not toggle when plugged into Linux. The NVIDIA control panel says that the monitor is connected and displays how many lanes are active and at what rate. Would the AUX log show you any more information about what is going on between the IP core and the graphics card that may shed light on what is going on? Thanks, Daniel
    • Deshi_Intel's avatar
      Deshi_Intel
      Icon for Regular Contributor rankRegular Contributor
      6 years ago

      Hi Daniel,

      The previous MSA log file dump is meaningful if the DP link training already happened and user just need extra info like validate the BPC setting, monitor the link BER rate, check for MSA lock status and etc.

      But from your issue description, looks like DP core is not transferring any data at all and somehow the link training is already stop or never started at all.

      • For Aux bus transaction monitoring, I use external protocol analyzer to decode the Aux transaction to provide meaningful data result to user.
      • For instance, I am using UNIGRAF DPA400 equipment to decode/debug DP AUX transaction
      • https://www.unigraf.fi/product/dpa-400-displayport-aux-channel-monitor/
      • Attached is sample log file for your reference. Then I can compare the passing log file vs failing log file to slowly isolate the issue

      Thanks.

      Regards,

      dlim