mITX: distorted video (popcorn pixels)

[asheplyakov]

Sometimes (approximately once in 5 boots) the screen looks like this:

• Both X and the (framebuffer) console look distorted.
• Temporarily switching off the monitor or re-plugging HDMI cable often fixes the problem.
• There's nothing special in the kernel logs
• The problem has been observed only with firmware from SDK-M-4.3. Happens mostly on mITX board (I've been able to reproduce it once on dbm too).
• Many output by efifb (verbose kernel logs) seems to provoke the problem. I.e. the problem happens
  more often when booting the kernel with the following arguments: loglevel=8 earlycon=efifb
• efifb itself works OK. That is, if I blacklist baikal_vdu_drm module the screen looks OK, and X starts and is usable (although the screen resolution is 800x600)