Comment # 12 on bug 72051 from Eugene Shalygin

Without the option, the message is not shown, but the HDMI screen is unusable:
every second or third frame is shown shifted by approx. 50 pixels downward.
When the screen is connected before boot, it is recognized always, but it does
not work every time when hot-plugged. So, in my case radeon.hw_i2c=1 seems to
be required option.