https://bugs.freedesktop.org/show_bug.cgi?id=108464
--- Comment #6 from Duncan Roe duncan_roe@optusnet.com.au --- (In reply to Duncan Roe from comment #3)
halt is fine btw, it's only reboot that breaks. Do you want extra debug turned on for dmesg?
At Linux 19.0-rc8, power button / halt command also fails. The backlight goes off but the power stays on.