I'm having issues with connecting the DART-MX8M board running Yocto to a HDMI screen. It works fine if I connect it to a HDMI monitor, but when I try to connect it to the display we want to use (HB-050WISB0GA0-B), it doesn't work, I see the following reported over the USB Debug cable:
[ 5149.145476] cdns-mhdp-imx 32c00000.hdmi: 0,ff,ff,ff,ff,ff,ff,0
[ 5149.151498] [drm] Cannot find any crtc or sizes
[ 5149.177868] cdns-mhdp-imx 32c00000.hdmi: 0,ff,ff,ff,ff,ff,ff,0
[ 5149.210668] cdns-mhdp-imx 32c00000.hdmi: 0,ff,ff,ff,ff,ff,ff,0
[ 5149.216635] [drm] Cannot find any crtc or sizes
[ 5149.221192] [drm] HDMI Cable Plug In
To set the HDMI output (works with HDMI monitor, just not this display) I used:
# cd /boot
# ln -fs imx8mq-var-dart-dt8mcustomboard-wifi-hdmi.dtb imx8mq-var-dart-dt8mcustomboard.dtb
The display itself works fine if I connect it to my laptop.
I saw this thread: https://community.nxp.com/t5/i-MX-Processors/HDMI-DRM-custom-resolution-and-clock-frequency/m-p/1029... which claims that I need to input timing parameters into the spreadsheet and then modify the kernel, but I've got no idea what many of the parameters are, and I can't find them on the datasheet:
Pixel encoding: RGB
Color depth: 8
Reference clock frequency [MHz]: ?
Expected pixel clock frequency [MHz]: 25.00?
Generated clock tolerance [%]: ?
Pll input divider: ?
Pll feedback divider: ?
Pixel clock divider: ?
Character clock divider: ?
I can get an edid file by:
# cat /sys/devices/platform/soc@0/soc@0:bus@32c00000/32e00000.display-controller/drm/card0/card0-HDMI-A-1/edid > ~/edid.bin
If I then parse that file with parse-edid < edid.bin, it reports this:
Checksum Correct
Section "Monitor"
Identifier "HDMI Panel W"
ModelName "HDMI Panel W"
VendorName "DWI"
# Monitor Manufactured week 9 of 2020
# EDID version 1.4
# Digital Display
DisplaySize 890 500
Gamma 2.20
Option "DPMS" "false"
Horizsync 14-70
VertRefresh 50-70
# Maximum pixel clock is 50MHz
#Extension block found. Parsing...
Modeline "Mode 2" 25.200 640 656 752 800 480 490 492 525 -hsync -vsync
Modeline "Mode 0" +hsync -vsync
Modeline "Mode 1" +hsync -vsync
Option "PreferredMode" "Mode 2"
EndSection
Please help.
Thanks
