Hi,

I recently bought Odroid N2+ (4GB) as a replacement for my raspberry pi 4. With legacy kernel 4.9 boars seems to be working fine. But when I flashed latest 5.10 kernel version it boots but without HDMI signal. I've read some topics here and in hardkernel forum and my conclusion is that my monitor resolution (3440x1440@60Hz) might not be supported by the kernel. I use this monitor. After some tinkering I was able to boot with video by passing following string to bootargs:

setenv bootargs ${bootargs} "video=HDMI-A-1:2560x1440@60"

Unfortunately the image is flickering and almost unusable in most cases.

 

Here is an excerpt from 4.9 kernel bootlog with deceted monitor parameters:

[    0.000000] Kernel command line: root=UUID=d73c1c90-ac2c-4d23-aa0c-a72348cdda9f rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty1 loglevel=1  no_console_suspend fsck.repair=yes net.ifnames=0 elevator=noop hdmimode=custombuilt cvbsmode=576cvbs max_freq_a53=1908 max_freq_a73=2208 maxcpus=6 voutmode=hdmi modeline=3440,1440,266570,74047,50,3440,3488,3520,3600,1440,1443,1448,1481,1,0,1 disablehpd=false  cvbscable= overscan=100 consoleblank=0
[    0.000000] vout: get hdmimode: custombuilt
[    0.000000] vout: get cvbsmode: 576cvbs
[    0.000000] max cpufreq of cluster0 : 1908000kHz
[    0.000000] max cpufreq of cluster1 : 2208000kHz
[    0.000000] hdmitx: voutmode : 1
[    0.000000] fmt_para.timing
[    0.000000]    - pixel_freq 266570, frac_freq 266570
[    0.000000]    - h_freq 74047, v_freq 50000
[    0.000000]    - hsync_polarity 1, vsync_polarity 0
[    0.000000]    - h_active 3440, h_total 3600
[    0.000000]    - h_blank 160, h_front 48, h_sync 32, h_back 80
[    0.000000]    - v_active 1440, v_total 1481
[    0.000000]    - v_blank 41, v_front 3, v_sync 5, v_back 33
[    0.000000]    - v_sync_ln 1
[    0.000000] fmt_para.hdmitx_vinfo
[    0.000000]    - name custombuilt, mode 0
[    0.000000]    - width 3440, height 1440, field_height 1440
[    0.000000]    - aspect_ratio_num 16, aspect_ratio_den 9
[    0.000000]    - video_clk 266570000
[    0.000000]    - htotal 3600, vtotal 1481
[    0.000000]    - viu_color_fmt 2, viu_mux 2

Is there anything else I can do to help you improve future kernels by supporting my monitor/resolution? Unfortunately I'm not a kernel hacker.

Mainline graphics drivers are not very good yet when it comes to "unusual" resolutions. Its the same for RK3399 and its Mali T860 chip. legacy works better there. There isn't much that can be done about besides waiting for better support.