https://bugzilla.kernel.org/show_bug.cgi?id=53111
--- Comment #6 from Alexander Mezin mezin.alexander@gmail.com 2013-02-19 14:55:44 --- Created an attachment (id=93541) --> (https://bugzilla.kernel.org/attachment.cgi?id=93541) Workaround
I found a workaround.
atpx->functions.power_cntl is 0 on my machine. Without this check switcheroo works again.
lspci: 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller (rev 09) Subsystem: Hewlett-Packard Company Device 3388 01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Whistler XT [AMD Radeon HD 6700M Series] (rev ff)
It's muxless system.