Problem with 4K output on Displayport (Haswell)

[esta]

hi,

 

i built a Mojave system on Haswell with HD4400,and i connected a display that support 4K resolution to display-port on this system.
then i got 4K Graphics output with 60hz refresh cycle rate.
everything is going well, i think.
however, the system have startup problem on display-port.

 

when i set the system resolution to 4k with 60hz rate and reboot , display-port outputs black screen.
but once restarted my display,it works fine.
It seems the frame buffer was initialized properly,but DP does not output when startup.
This issue does not occur if the refresh rate is 30hz.

 

If someone has a similar problem, please let me know a valid patch or solution.

 

I did the following for enabling 60hz cycle rate.

・set the "enable-hdmi20" property to config.plist
・set the frame buffer size to 32MB

 

Regards