I want disable the HDMI hotplug detect and always keep HDMI output 1080P video in Framebuffer Mode.
Does your monitor support 1080p? Could you add one more node “display-timings” under “hdmi-display” in device tree and see if it works?
You could also try to set it manually.
#pick 1080p mode
echo #that mode > /sys/class/graphics/fb0/mode