Comment 62 for bug 1283938

I'm using Ubuntu 14.04 64-bit (out of the box, updated) and I'm having the same issue. My hardware is a laptop Asus with AMD A8-4500M Trinity APU (Radeon HD 7640G) and updated BIOS. To make some Fn keys work I had to add "acpi_osi='!Windows 2012' to my grub command line, I'm dual booting Windows 7.

I have been making some research and, as of now, I can confirm this problem wasn't present in ubnutu 12.04 with original HWE stack. For this APUs, 14.04 is a major step forward in terms of power management and 3D acceleration, so I can't go back to 12.04, because sometimes I really have to push my hardware to its limits (working with GIS software) and 12.04 fan speed is always high and noisy. I can confirm the same behavior is present in Manjaro Linux Xfce with kernels 3.12 to 3.14. In Ubuntu, changing HWE stack to previous releases the problem is present too (from quantal to my knowledge). So, I'm not keeping my fingers crossed with this bug.

I have tried a lot of workarounds: disabling lightlocker, unpicking options in lightlocker settings, uninstalling pm-utils, forcing nomodeset, scripting power management brightness... but nothing seems to work. We need heavy help!