HPD for Displayport on custom Board not working

Hi,

we have a custom carrier board where we want to use the Displayport.
The problem is that the HPD is not working at all, I am using the dp_aux_ch0_hpd_pp0 pin.

When i use the HPD as a GPIO and see the values, i can see changes in the pin.
So when i check it with “cat /sys/kernel/debug/tegra_gpio” I can see the following:
“P:0 0x1 0x0 0x1 0x1 0x0 0x0”
And
“P:0 0x1 0x0 0x0 0x1 0x0 0x0”
When plugging / plugging out the cable.

But when i try to use this pin for HPD it is not working at all, i do not even see any dmesg or kernel message when plugging in the cable.
Do you have any idea how i can solve this issue?
I also checked if the rest of the Displayport, so I did some work in the Kernel on the dp.c file, where i disabled the checking for “DPAUX_DP_AUXSTAT_HPD_STATUS_PLUGGED” state.
Then i can get the whole Displayport working and I see a console on the Screen.
So it seems that just the HPD port is somehow not configured correctly or not setup correctly.

Thanks!
Best Regards,
Simon

Is this a Jetson TX2 or some other modules?

Hi,

it is a TX2 module and we are using it with L4T 28.1.0.

Best Regards,
Simon

Hi,

I know this may not be related to the original topic, but are you really sure you want to use such old release that was released for like 4 years ago? Lots of bugs/issues may have been resolved in later release.

Hi,

unfortunately for now we have to use such an old release.
We are planning to update the L4T in the future, but not now.
So for now we want to use the Displayport with such an old release of L4T, if it is possible.
Or do you know of any limitations or bugs regarding it in this old Release?

Best Regards,
Simon

Honestly, I cannot remember. This is really very long time ago.

From software side, please clarify what device tree change you have added to the board.
Did you remember to change the pinmux?

From hardware side, please refer to the TX2 product design guide.

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