Two lanes eDP lcd for Xavier NX trouble

Hi ,
We want to use an eDP interface lcd for Xavier NX,
the eDP LCD has two lanes : lane0 and lane1, aux_ch, hpd,
use the Jetson_Xavier_NX_Carrier_Board’s DP port for testing,
connect eDP lcd’s lane0 , lane1, aux_ch, hpd, and vdd to carrier board DP port’s LANE0, LANE1, AUX, HPD, and PWR, LCD’s backlight always on, after system power on, no display on the LCD, and the dmesg log and LCD spec attached bellow, please give some advice, thanks.


edp-second (68.8 KB)

Tegra fails to read the EDID from your panel. Please check your hardware design for this part.

[    1.706359] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[    1.706786] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000
[    1.706969] hpd: switching from state 2 (Check EDID) to state 2 (Check EDID)
[    1.713331] hpd: state 2 (Check EDID), hpd 1, pending_hpd_evt 0
[    1.718277] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[    1.718674] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000
[    1.718864] hpd: switching from state 2 (Check EDID) to state 2 (Check EDID)

Thanks, I find this, and checked the AUX_ch connect OK.
I use FPC to DP plug converter(FPC to eDP LCD and DP plug to carrier board DP port), so the carrier board DP’s pin 13, and pin 14 connect to GND, does this matter?

It depends on your eDP device feature. Pin 13 has no effect to Jetson. DP_MODE pin is connected to GND on carrier board.

Also, you can probe the AUX lines with scope to observe if any communication on it.

If your power source is a always-on system power with 3.3v, please also check the device tree setting of vdd-dp-pwr-supply.

hardware/nvidia/platform/t19x/jakku/kernel-dts/common/tegra194-p3509-disp.dtsi

Hi,
I use the debug uart for log
when plug the DP plug
got debug log bellow

[   53.446962] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[   53.447341] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000
[   53.458933] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[   53.459314] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000
[   53.470886] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[   53.471292] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000
[   53.482961] tegradc 15210000.nvdisplay: dp: aux read failed (0x10040000
[   53.483350] tegradc 15210000.nvdisplay: dp: Failed for I2C read addr:80, size:0, stat:0x10000000

I just swap the AUX_P and AUX_N connect, replug the DP plug
got bellow log

[  460.385806] tegradc 15210000.nvdisplay: dp: aux write got error (0x10000100)
[  460.385967] tegradc 15210000.nvdisplay: dp: Failed to write DPCD data. CMD 0x600, Status 0x10000100
[  460.391160] tegradc 15210000.nvdisplay: dp: aux write got error (0x10000100)
[  460.391324] tegradc 15210000.nvdisplay: dp: Failed to write DPCD data. CMD 0x600, Status 0x10000100
[  460.396725] tegradc 15210000.nvdisplay: dp: aux write got error (0x10000100)
[  460.396890] tegradc 15210000.nvdisplay: dp: Failed to write DPCD data. CMD 0x600, Status 0x10000100
[  460.402170] tegradc 15210000.nvdisplay: dp: aux write got error (0x10000100)
[  460.402315] tegradc 15210000.nvdisplay: dp: Failed to write DPCD data. CMD 0x600, Status 0x10000100
[  460.402508] tegradc 15210000.nvdisplay: dp: failed to exit panel power save mode (0xfffffff2)
[  460.402655] hpd: edid read prepare failed

So does it means, after swap AUX_P and AUX_N, LCD and NX communication is OK?
And any advice next? Thanks

Just want to clarify, are you still using the Jetson Xavier devkit here?

Yes, just swap the LCD to DP adapter‘s AUX P and N

Where does the power source of this panel come from?

It is powered by the NX carrier board’s DP port

Could you share the full dmesg of current status?

after power on the debug uart log as bellow
edp-auxswap-log.txt (39.5 KB)

Debug uart log is not full log. Please use command dmesg to share log.

dmesg log as bellow, Thanks
swapaux (113.0 KB)

hi, any clues, thanks

Hi, your test setup is by such wires not cable? I’m afraid that its signal quality will be not so good. For AUX connection, it should work if your device power on correctly and AUX connection is correct. And we are not sure if your such 2 lane eDP is supported as you can see in DG that it is 4 lane connector on devkit.

So, please try to make the AUX of the LCD work firstly.

Thanks. I will check the AUX wire first.
But do you know the AUX communication frequency?
If the frequency is not high, I think it doesn’t matter.

It is like I2C.

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