[amd] screen-unblanking seems to flicker backlight on/off 8 times before display resumes

[Gerry Boland]

I've a Lenovo Flex 2-14D which has an AMD GPU. I'm using the free driver. I have unity8 installed.

If I let the screen blank, and hit a key to unblank, it takes about 5 seconds until screen turns on properly. During those 5 seconds, I see the display backlight turn on & off about 5 times, all the while with a black picture.

[Daniel van Vugt (vanvugt)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. Please execute the following command only once, as it will automatically gather debugging information, in a terminal:
apport-collect 1667001

When reporting bugs in the future please use apport by using 'ubuntu-bug' and the name of the package affected. You can learn more about this functionality at https://wiki.ubuntu.com/ReportingBugs.

[Daniel van Vugt (vanvugt)]

Oops, sorry Gerry. Didn't realize it was you :)

[Alexandros Frantzis (afrantzis)]

Could you please attach /var/log/repowerd.log at the time of the issue.

[Gerry Boland (gerboland)]

@alf:
http://pastebin.ubuntu.com/24053520/

[Gerry Boland (gerboland)]

Ok, with Alexandros' help I've dug a bit more.

On my hardware, I tear everything down and just run
    sudo mir_demo_server_basic --arw-file
I can see clients ok.

I forked mir_demo_client_display_config to add extra bits:
https://code.launchpad.net/~gerboland/+git/display-configurator
which adds an "O" option to power off the display

When I run it, and hit "O", the display flickers 8 times and then stays off (mir_power_mode_off)

If I hit "P" to turn it on again, nothing happens (mir_power_mode_on). Applying the configuration appears to hang the client - I get no success or fail response from Mir.

If I kill the client, Mir re-activates the display (flickering 8 times)

[Gerry Boland (gerboland)]

One small warning message is printed during display on flicker:
http://pastebin.ubuntu.com/24053776/

[Daniel van Vugt (vanvugt)]

That warning might indeed correlate with some flicker:

[2017-02-23 16:18:58.483124] <WARNING> mesa-kms: drmModeCrtcSetGamma failed: Invalid argument