Switching graphics between the A8-6410 APU with integrated R5 Mullins + dedicated R5 M240 Hainan is not working(HP 355 G2 notebook). I think it's because the dedicated gpu for some reason can just not be activated, because "/sys/kernel/debug/vgaswitcheroo/switch" and the Radeon Profile tool show two gpus, but changing the gpu state from "off" to something else within Radeon Profile doesn't work for the dedicated one.
I tried the gearsongallium livecd with very recent drivers/Xorg/etc.

Versions included in the gearsongallium livedvd i tested:
Mesa-git – 10.5_git2015.02.04
Kernel – 3.19-rc6
libdrm – 2.4.99_git2015.01.22
Mesa-demos – 9.1.0_git2014.07.06
xorg-server – 1.16.99.9
xf86-video-ati – 7.99.99_2015.01.15

I also tried in Kubuntu 14.10 to switch with DRI_PRIME=1. If i do that i get corrupt window and lower fps than with integrated gpu with es2gears. However "DRI_PRIME=1 glxinfo" says it's using the dedicated gpu.
In gearsongallium i get the same output with or without "DRI_PRIME=1 glxinfo" so it seems to not switch at all with recent drivers/Xorg/etc.

I can also post Xorg log and dmesg output, but i couldn't spot anything unusual there looking quickly through it. However "dmesg|grep -i vga" might be important:
$ dmesg |grep -i vga
[    1.069056] vgaarb: setting as boot device: PCI:0000:00:01.0
[    1.069061] vgaarb: device added: PCI:0000:00:01.0,decodes=io+mem,owns=io+mem,locks=none
[    1.069077] vgaarb: loaded
[    1.069080] vgaarb: bridge control possible 0000:00:01.0
[    1.763179] fb0: EFI VGA frame buffer device
[    2.029145] ACPI: Video Device [VGA] (multi-head: yes  rom: no  post: no)
[    2.115398] VGA switcheroo: detected switching method \_SB_.PCI0.VGA_.ATPX handle
[    2.191102] ACPI: Video Device [VGA1] (multi-head: yes  rom: no  post: no)
[    2.255714] fb: switching to radeondrmfb from EFI VGA
[    2.440405] [drm]   VGA-1
[    2.527423] vga_switcheroo: enabled