HDMI Display Data Channel Errors

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
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1

Hi,

we have designed a custom carrier board for the Jetson Xavier NX where we face problems with HDMI.

I appended the complete output of dmesg during boot with the error messages.
dmesg.log (78.2 KB)

The problem seems connected to DDC not being able to use I2C for reading the EDID considering the following extract from dmesg output:

[   24.411661] tegra-i2c 3190000.i2c: rx dma timeout txlen:28 rxlen:128
[   24.411807] tegra-i2c 3190000.i2c: --- register dump for debugging ----
[   24.411933] tegra-i2c 3190000.i2c: I2C_CNFG - 0x22c00
[   24.412022] tegra-i2c 3190000.i2c: I2C_PACKET_TRANSFER_STATUS - 0x10001
[   24.412138] tegra-i2c 3190000.i2c: I2C_FIFO_CONTROL - 0x0
[   24.412229] tegra-i2c 3190000.i2c: I2C_FIFO_STATUS - 0x800080
[   24.412325] tegra-i2c 3190000.i2c: I2C_MST_FIFO_CONTROL - 0x70
[   24.412423] tegra-i2c 3190000.i2c: I2C_MST_FIFO_STATUS - 0x7c0000
[   24.412538] tegra-i2c 3190000.i2c: I2C_MST_PACKET_TRANSFER_CNT - 0x0
[   24.412649] tegra-i2c 3190000.i2c: I2C_INT_MASK - 0x6c
[   24.412739] tegra-i2c 3190000.i2c: I2C_INT_STATUS - 0x2
[   24.412843] tegra-i2c 3190000.i2c: i2c transfer timed out addr: 0x50

This (timeout) error occurs periodically. After some time, the following message occurs:

[  116.574605] tegradc 15200000.nvdisplay: hdmi: edid read failed
[  116.574787] tegradc 15200000.nvdisplay: hdmi: using fallback edid

After that the video output via HDMI is stable with a fallback resolution of 720p. So, we get video output via HDMI, but it is important that DDC is working correctly, and the EDID of the display is read.

Here is the output from i2cdetect -l showing the I2C devices available in L4T:
i2cdetect

The signals on our carrier board are connected as shown in the following image (HDMI_Signals_Schematic.png):

HDMI_Signals_Schematic
HDMI_Signals_Schematic866×892 79.2 KB

As I understand section ‘8.2 HDMI’ in Jetson_Xavier_NX_Product_Design_Guide_DG-09693-001_v1.6.pdf this should be a working configuration.

We used the default device-tree sources provided for the Jetson Xavier NX Dev-Kit (Jakku).

Any ideas on why we face these DDC errors would be very much appreciated!

Best regards
Bruno

3

According to past experience, such DDC error is due to hardware design problem.

If you are using the default device tree from jeptack, then SOR1/DP1 is for HDMI, and software controller is tegradc 15200000.

Thus, software does not have anything to configure here.

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