HDMI custom timings

[Toboe]

tl;dr: I have a cheap, no-brand monitor that is 2560x1440 and I guess uses some less-than-standard HDMI timings because it's not plug'n'play with my rpi or tinkerboard. I want to know how to hard-code the HDMI timings on the tinkerboard because I think that's how I got it to work with the rpi.

On my rpi, I was able to get it to work by adding the following lines to the rpi's /boot/config.txt:

Code:

hdmi_cvt=1440 2560 30 3 0 0 0
hdmi_group=2
hdmi_mode=87
hdmi_timings=1440 1 96 64 160 2560 1 27 24 6 0 0 0 30 0 138000000 3
display_rotate=1

Which I got by using an edid parser (note this board is natively portrait, not landscape, so it is 1440x2560, not 2560x1440, thus the order in the hdmi_cvt/hdmi_timings and the rotate)

Then I added a matching display mode to /etc/fb.modes and everything worked great on the rpi other than the performance

On the tinkerboard, I updated to the 2.0.3 beta, used the

Code:

sudo tinker-config

command and got a /boot/config.txt file. I naively tried adding the same lines that worked on the rpi to that file, but those weren't picked up. I'm not even sure if it'll be possible for those to be implemented on the tinkerboard in the future, so I'm not going to hold my breath waiting for them to be supported.

Elsewhere on the forum, I saw someone suggesting to add something like the following to the "append" line in /boot/extlinux/extlinux.conf:

Code:

video=HDMI-A-1:1440x2560@30

This did not help (I also tried 2560x1440 just for fun, no result there either... is there a syntax guide for this anywhere? can I do anything other than WxH@FPS?). Prior to adding this, it looked like the resolution negotiation was happening, at least I'm guessing that's what was causing the backlight for the monitor to turn on and off and then on again with the screen staying blank. But after adding this, not even the backlight turns on.

I should note that running

Code:

fbset

on the rpi returns that the display depth is 24 with no coaxing, meanwhile on the tinkerboard it seems to automatically go to 32, ignoring whatever is put in /etc/fb.modes. I believe the right value is 24 since the rpi is working. I can manually update it on the tinker board using

Code:

fbset -depth 24

though the display still doesn't work after doing that.

I saw on the Android forum some talk of compiling the Android kernel or something like that to hard-code the HDMI timings in, but I'm not sure where to start to do that for Debian. If that's the way to go, is there a guide somewhere? Or is there something else I can try?

---

Edit: found this link in several places on this forum (feel pretty dumb now that I didn't find that sooner): https://qiita.com/mt08/items/890a71d0b399ac1a9b49
Which does still work for 2.0.3 with some minor changes:

I had to also add this line:

Code:

EXTRA_CFLAGS += -Wno-misleading-indentation # GCC6

to the following files:

• drivers/net/wireless/rockchip_wlan/rtl8814au/Makefile
  
• drivers/miniarm/rtl8723bs/Makefile
  

In addition to the file drivers/net/wireless/rockchip_wlan/rtl8723bs/Makefile which the linked guide already covers.
After that, everything else about compiling and installing from that link worked. Wireless still worked (which based on what I've seen in other threads tends to be a problem) so I'm guessing most stuff is working.

I will update again after I test doing the same type of code changes as documented in this comment.