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VESA 1280x1024 with h3disp


gnasch
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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

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@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

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