I have an HP laptop with dual AMD graphics cards (radeon HD 6520g + HD 6750M) running Ubuntu 13.10 beta1, kernel 3.11.0-7-generic amd64. This command # echo "OFF" > /sys/kernel/debug/vgaswitcheroo/switch throws a WARNING in the kernel logs, after which the folder /sys/kernel/debug/vgaswitcheroo/ and the dGPU disappear (as noted in the logs) (and power usage is notably lowered, guessing from the temperatures). dmesg: http://pastebin.com/Pb7ELyqP , lines 1196+ Someone else in the #radeon channel also found this report: http://lists.freedesktop.org/archives/dri-devel/2013-September/045157.html which links to another old report from the same person. Thanks.
Seems to have been fixed in kernel 3.12-rc1 (from http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.12-rc1-saucy/ ). I don't know how to test it in a better way (other than simply running the above command)... and I don't have other hardware to test it, so please close it if you think it should be closed.
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