In a nutshell, it looks to me like this feature was broken somewhere between kernel releases 3.16 (working) and 3.19 (not working), POSSIBLY in combination with having a machine that has a BIOS version newer than mid-2015 when vendors updated their BIOS with the VU#976132 fix.
I'll try to reproduce the problem on kernels v3.17.1-utopic and v3.18-vivid.
In a nutshell, it looks to me like this feature was broken somewhere between kernel releases 3.16 (working) and 3.19 (not working), POSSIBLY in combination with having a machine that has a BIOS version newer than mid-2015 when vendors updated their BIOS with the VU#976132 fix.
I'll try to reproduce the problem on kernels v3.17.1-utopic and v3.18-vivid.