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.