[Bug 74551] Unable to run linux with radeon.runpm=1

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=74551

--- Comment #15 from Alex Deucher <alexdeucher at gmail.com> ---
(In reply to maxis11 from comment #13)
> (In reply to Alex Deucher from comment #12)
> > (In reply to maxis11 from comment #6)
> > > BTW runpm works with 3.12.7 and 3.12.8 (with 3.13 and later runpm=1 freezes
> > > laptop during boot)
> > 
> > runpm support didn't exist until 3.13. If "echo OFF >
> > /sys/kernel/debug/vgaswitcheroo/switch" has never worked, then your system
> > has never had functional support for turning on/off the dGPU.
> 
> kernel 3.12.7:
> When loading SUMO2(6480g)

That's not runpm, that's dpm (dynamic power management).  Runpm turns the dGPU
off completely when it's not in use.  Dpm dynamically adjusts the clocks and
voltages of the GPU when it's powered on.  Prior to 3.13, runpm was not
available and the dGPU was always powered on unless you manually powered it off
via debugfs.

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