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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 plug a Windows PC (7 or 10) into the daughter card it immediately performs the link training and connects to the Operating System. Using SignalTap I can see data flowing out of the Clkrec core (VSYNC, HSYNC, DE, Data). When I plug in a monitor to the TX port I can see a windows desktop as if it were a second monitor to my Windows PC desktop.

 

When I plug a linux machine (or same hardware but dual boot) into the DisplayPort RX port, Linux recognizes the DisplayPort sink as a monitor. However I am not seeing any data come out of the Bitec Clkrec.

 

Linux is reporting that it found valid modes for the DisplayPort monitor.

 

Can you help me figure out why the DisplayPort core has no trouble connecting to Windows but has trouble connecting to Linux?

 

Setup:

OS: CentOS 6

Graphics Card Vendor: NVIDIA

DisplayPort Core: GPU mode enabled, AUX debug enabled, core is set for HBR3 and 4k60 resolution.

Tool: Quartus 19.1

 

Thanks!

Daniel

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Moderator
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Re: DisplayPort Only Connects to Windows not Linux

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

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Moderator
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Re: DisplayPort Only Connects to Windows not Linux

posted a file.
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Novice
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Re: DisplayPort Only Connects to Windows not Linux

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
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Re: DisplayPort Only Connects to Windows not Linux

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

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Novice
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Re: DisplayPort Only Connects to Windows not Linux

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
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Moderator
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Re: DisplayPort Only Connects to Windows not Linux

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

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Novice
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Re: DisplayPort Only Connects to Windows not Linux

Hi Dlim,

 

I don't have a unigraf analyzer but can provide the AUX logs that the NIOS II prints out. Would that be useful? Would you like both the working Win7 and not working CentOS logs?

 

Thanks,

Daniel

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Re: DisplayPort Only Connects to Windows not Linux

 

Here is the NVIDIA Control Panel showing that the DP output is using 4 lanes all at 8.1 Gbps.

NVIDIA Control Panel.png

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Re: DisplayPort Only Connects to Windows not Linux

Hi Dlim,

 

  1. I have tried this and it didn’t seem to make a difference
  2. I am recompiling with the lower data rate set to try it out. Are the only changes to the IP core data rate settings or do I need to make changes in the RTL as well?
  3. I am downloading Quartus Pro v20.2 (Stratix 10 file is over 20 GB) and will try that out once it finishes downloading.
  4. We are targeting and doing the bulk of the testing with an NVIDIA RTX 6000 Graphics card. I have also been testing with a Geforce 660 Ti. The monitor I am using in conjunction with the IP core is a Dell U2718Q.
  5. The logs are attached.

 

The AUX logs are for linux and windows for both the GeForce 660 and the RTX 6000. The only combination that has data flowing out of the clkrec core is the Geforce 660 running win7.

 

Thanks,

Daniel

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Novice
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Re: DisplayPort Only Connects to Windows not Linux

Hi dlim,

 

Installing the Stratix 10 device file for Quartus Pro v20.2 is taking longer than I expected. It is 20 GB and exceeds the download file size allowed by my company. Are there plans to break up these larger device files into multiple parts in the future releases?

 

Thanks,

Daniel

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Re: DisplayPort Only Connects to Windows not Linux

Hi dlim,

I have successfully installed Quartus v20.2 on my PC. I created a new DisplayPort sample project in Quartus v20.2 and merged in the new IP cores and software into my current design. When I try to compile it I have been experiencing an error when "Route" reaches 53%. I am not sure why this is happening now. I am attaching the stack trace displayed when crashing.

Originally I thought this was due to some port names being renamed from the cores. I cleaned that up in my RTL and it is still giving me this problem.

Any clue why this might be happening?

Thanks,
Daniel

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Re: DisplayPort Only Connects to Windows not Linux

Hi dlim,

 

I got the project to compile but it stopped 2 more times in different spots with similar stack traces on the way.

 

When I loaded the compiled design from v20.2 I see similar results. Linux recognizes the DP interface but the clkrec core does not output anything.

 

I am attaching the AUX log from the v20.2 load connecting to Linux on the RTX 6000.

 

Thanks,

Daniel

 

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Moderator
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Re: DisplayPort Only Connects to Windows not Linux

Hi Daniel,

Sorry for the late respond as we were having big Intel forum maintenance update for the last week.

A lot of things mess up and some info are lost as well. Pls give me sometime to sort thing out internally and work on the manual clean up first.

Also sorry, I may need to request you to resend me some info again due to info lost during maintenance update.  

So, I will get in touch with you again next week to resume our debug discussion. I will let you know by then what are the missing info that I need.

Thanks.

Regards,

dlim 

 

 

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