Nvdc failed to open /dev/tegra_dc_ctrl

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
1

Hi,

We’ve been working on a prototype device using a Jetson Xavier NX Dev kit. Recently we suddenly started observing the following error popup at boot.

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Investigations and search around the existing topics have led us to identify the /etc/profile.d/jetson_env.sh hence jtop as the component triggering the issue, as in not observing the error popup when jtop is uninstalled.
While still investigating, it remains nebulous to us why we started observing this. Power supply related testings were performed recently, although it is not clear to us if a causal link exists.

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Here are our questions:

  • Any hints as to why we might be observing this?
  • Is jtop actually accessing the /dev/tegra_dc_ctrl device? If so for what purpose?

Thanks.

2

  1. Did you remember what was installed on your side to trigger this issue?

  2. jtop is actually not NVIDIA official tool… it is a tool released by other developers active on this forum.
    If you hit any new issue in jtop, please check their github.

3
  1. Nothing new seems to have been installed which could have triggered the issue around the time we started oberving this. Jtop was installed 1.5 yrs ago.
  2. Yes indeed, thanks. The rephrased question is what is the /dev/tegra_dc_ctrl device implementing? Given that the cdev permissions have not changed, what could cause any 3rd party tool to fail accessing the device?
    Thanks @WayneWWW.
4

Hi,

Tegra dc means tegra display controller. These are the display driver to init and enable display. nvdc is a userspace library that can communicate between userspace and kernel driver.

Actually, this is not my first time seeing this error coming out. However, what I still don’t know is how you guys hit this issue or how to reproduce this issue.

Could you clarify what is the exact scenario to hit this error? When you opened jtop, it would immediately show this? Or even the desktop gui fails to show and gives you this error?
What is your method to resolve it? by uninstalling jtop?

5
  1. The popup ONLY appears at boot, once we dismiss the window, we reach the desktop gui. Jtop can successfully be launched afterwards, no other apparent problem.
  2. To reproduce the issue on our side, we simply need to have jtop installed. To prevent this we do uninstall jtop for now.
    Thanks @WayneWWW .
6

And this is rel-32.6.1?

7

Yes indeed:

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8

I will try some new jetpack release with jtop on my side. If this would not reproduce on new release, then I could only suggest you upgrade the version.

9

We do have at least 2 other identical prototypes with the same L4T release. They do not have this issue.

On the hardware side of things there were some testings around the time we started seeing the issue:

  1. power supply related manipulations (AC vs battery powered), removing the battery etc
  2. connected to different screen models, with/without an hdmi splitter etc

Can this originate from hardware config/defect?

11

Nope. This is most likely a pure software issue.

15

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