IMX8M Nano HDMI not working with HDMI-LVDS bridge Board

[RDSIMARIA]

Hi Team,

I am currently working on IMX8M nano evk kit. I have loaded prebuilt Andorid (Pi) images on board. I have connected DSI to MIPI SaS connector with Board

1. When i connect HDMI port to Monitor, it is working properly. i am able to see Android GUI properly

2. When i connect HDMI port to HDMI-LVDS Bridge i am not getting any output on LVDS Display (While this bridge working properly with my laptop HDMI connector i am able to see windows 10 gui on screen)

3. When i connect HDMI port to Monitor and let board bootup then remove hdmi from monitor and connect to HDMI-LVDS Bridge in between t is working properly.

[RDSIMARIA]

Hi Joanxie,

Let me share you diagram which makes thing easier to understand. I have attached Diagram

Currently i am able to connect hdmi out to Monitor properly. But when i connect to our custom board it is not working.

But when i first connect to monitor and then custom board without rebooting it is working properly

[joanxie]

if you connect your convert board(hdmi to lvds) with mipi to hdmi board, then boot up the board failed, but when you connect the hdmi with hdmi to lvds board, the boot up successfully, then you connect your own board(hdmi to lvds), doesn't reboot the board, the lvds can work, am I right? if yes, when the board failed, did you get any error message? could you share the logfile?

[RDSIMARIA]

Hi JoanXie,

I found below error logs related to EDID

[ 1.359441] [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
[ 1.366080] [drm] No driver support for vblank timestamp query.
[ 1.372099] imx-drm display-subsystem: bound imx-lcdif-crtc.0 (ops lcdif_crtc_ops)
[ 1.379938] imx_sec_dsim_drv 32e10000.mipi_dsi: version number is 0x1060200
[ 1.387521] imx-drm display-subsystem: bound 32e10000.mipi_dsi (ops imx_sec_dsim_ops)
[ 1.408782] imx-drm display-subsystem: HDMI-A-1: EDID is invalid:
[ 1.414907] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.421471] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.428008] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.434559] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.441110] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.447648] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.454184] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.460720] [00] ZERO 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[ 1.471076] imx_sec_dsim_drv 32e10000.mipi_dsi: no bus formats assigned by connector
[ 1.504886] imx_sec_dsim_drv 32e10000.mipi_dsi: no bus formats assigned by connector
[ 1.530908] Console: switching to colour frame buffer device 128x48
[ 1.530934] imx_sec_dsim_drv 32e10000.mipi_dsi: no bus formats assigned by connector
[ 1.576215] imx-drm display-subsystem: fb0: frame buffer device
[ 1.582715] [drm] Initialized imx-drm 1.0.0 20120507 for display-subsystem on minor 0

[joanxie]

what timing do your hdmi to lvds board need? you can check the HDMI signal is correct or not, it seems the signal isn't correct, since you use your own board, you need debug it by yourself

[RDSIMARIA · Accepted solution]

Hi Joanxie,

Thanks for your reply.

1. Can you provide any documents related to HDMI i can start exploring our hardware.

2. Can i use default EDID as suggested in Kernel Documentation?

[joanxie]

I really suggest that you can refer to this document

"https://community.nxp.com/t5/i-MX-Processors-Knowledge-Base/IMX8MM-MIPI-DSI-to-LVDS-bridge-board-sup..."

[joanxie]

what HDMI-LVDS Bridge  do you use? current bsp only support mipi to lvds bridge, if you use new bridge, I think you need add this in the dts file