VESA 1280x1024 with h3disp

[gnasch]

Hello,

today I want to connect the OpiPcPlus to a Flexscan S1921 Monitor.

I select h3disp -m 33 -d to use my *tested* hdmi-to-dvi cable and reboot.

Now the monitor complains:

fV:  59.9 Hz

fH:  63.9 kHz

fD:  161.7 MHz  ****red***

 

this seems too high because VESA mode should use a pixel frequency of 108MHz which is also the spec of the monitor.

 

1280x1024 @ 60Hz (VESA) hsync: 64.0kHz 	1280x1024	108.0 1280 1328 1440 1688 1024 1025 1028 1066 	+hsync 	+vsync 

The pixel frequency seems too high for the 60 Hz image refresh, it corresponds to 85 Hz.

I am using legacy kernel:

Linux JagOpi 3.4.113-sun8i #10 SMP PREEMPT Thu Feb 23 19:55:00 CET 2017 armv7l GNU/Linux

 

Any ideas?

Thanks,

gnasch

[gnasch]

bump - where could I find the relevant kernel sources? Did the armbian project patch this legacy kernel?

Thanks

gnasch

[tkaiser]

The HDMI relevant patches can be found here: https://github.com/igorpecovnik/lib/tree/master/patch/kernel/sun8i-default, kernel is pulled from there: https://github.com/igorpecovnik/lib/blob/master/config/sources/sun8i.conf#L10-L11 and there is an open bug report regarding h3disp: https://github.com/igorpecovnik/lib/issues/624

 

 

[gnasch]

@tkaiser: thank you very much for your help. I was able to track down the bug. Contrary to first belief, the kernel is not concerned, but in h3disp on line 196 the pll_video is initialized to 646 MHz. With kernels divisor of 4 this results in pixel frequency of 161.5 MHz, which is too high for Vesa 1280*1024.

So I  replaced this initialization with 432 MHz, which results in correct fD of 108 MHz. Now the monitor synchronizes.

Unfortunately I found a bugfix by @igor on 24.Oct.2016 which inserted the 646 MHz value. I could not read the reasoning behind this (facebook srsly?), so I would kindly ask to revert this change if no important reasons for it exist.

 

best wishes and thanks to armbian team for your great work!

gnasch

[tkaiser]

https://github.com/armbian/build/commit/906528a03fa361447def71757d0c0ce746e55177#commitcomment-22046840

 

Please use Github if you want something to change. Information/requests in random forum posts might get lost.

[gnasch]

Thank you, will try to do so next time!

gnasch

[ludwich]

I changed the value in h3disp manually to 432MHz (-m 33 -d). Now my Display DELL108FP (1280x1024 @60Hz) works well too.

 

ludwich