[Bug 81021] AMD CPUs w/ Integrated Graphics (APUs) And Turbo Core Only Boost If "fglrx" Module Is Loaded

[bugzilla-daemon at bugzilla.kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=81021

--- Comment #5 from LiNuxXer <andre.d at gmx.net> ---
(In reply to Kertesz Laszlo from comment #3)
> This issue isnt new, i filed a bug about it ages ago ( #62861 ). As Alex
> said, turbo core can be enabled by setting bapm  to true.

I cannot see any relation between this bug and #62861.

Over there, you stated:

> This issue is related to the radeon driver's dpm code.
> If i dont append radeon.dpm=1 to the kernel boot options, i have
> 0.9-1.34v and correct CPU speeds (including torbo boost).

This bug report here is about Linux not supporting Turbo Core on APUs when no
specific graphics driver is used.

In other words, I'm raising the question whether the kernel should be able to
suipport the APU Turbo Core even without any specific graphics driver.

> [...]
> Also, a simpler way of seeing the actual working frequency is loading the
> msr module:
> 
> modprobe msr
> 
> Then running:
> 
> cpufreq-aperf

In what regard is this simpler than using cpupower?

> Additionally, even if fglrx eables turbo core boost, sometimes something
> weird happens and even the nominal speed is reported as maximum, in effect
> you can have even as low as 1.8 GHz (3.2GHz CPU) after an initial turbo
> boosted speed which lasts a few seconds. This happened to me sometimes
> (almost 50% of times) when i was compiling with 4 threads on my older
> A8-5500. I suppose its some internal downclocking mechanism kicking in at
> the wrong time because the reported temperatures were ~55C (default cooler).

I stress tested the A10-6700 with fglrx loaded (but console only video) and two
cores with 100 % load can boost to 4300 MHz seemingly forever, three with 100 %
load will be boosted to 3900 MHz.

> In contrast this never happened with radeon and if one thread was used it
> could have 4 GHz for hours (runaway flash in browser for example).

Maybe the radeon driver didn't load the GPU as much as the fglrx driver did.
But since I'm going for console output only, I don't mind. If there's just one
bit controlling this behaviour, we'll have to live with the APU's autonomous
decision. Some may be smarter than others and maybe it even depends on cooling.

Still, I would appreciate my 3700 -> 4300 MHz boost for two cores.

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