** Also affects: linux (Ubuntu Trusty)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1416451
Title:
Can't switch display mode more than one cycle when docked
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Trusty:
New
Bug description:
[Impact]
We have a system under certification that needs a workaround in the kernel
for now. The bug is that if the machine is booted attached to a dock with a
monitor connected to it's VGA output, the connection to the monitor is dropped
after one full cycle of display modes with the hotkey combo. This is a firmware
bug and will eventually be fixed by the BIOS vendor, but in the meantime we
need a workaround in the kernel.
The dock has a builtin DP-VGA dongle which is the culprit here.
[Test Case]
attach the unit to a doc with a monitor plugged to a VGA port, switch display
modes with hotkey combo, should be able to do more than one cycle with the combo
[Regression Potential]
We got the patch from Intel, with this disclaimer:
"The workaround in comment 41# maybe has side effect on DP port which doesn't
connect DP screen. On these DP ports, this workaround will add an extra power
on and power off command . So this workaround couldn't push to upstream."
so there shouldn't be any visible regressions..
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