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

[bugzilla-daemon@bugzilla.kernel.org]

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

Kertesz Laszlo <laszlo.kertesz@gmail.com> changed:

           What    |Removed                     |Added
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                 CC|                            |laszlo.kertesz@gmail.com

--- Comment #3 from Kertesz Laszlo <laszlo.kertesz@gmail.com> ---
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.
Now this is enabled on MSI boards (seems to me all had A78 chipsets?) only by
default because they had reboots right after boot if it was off.
Im curious how they fare with enabled bapm.

Problem is setting bapm on, at least on my A8-6500/GA-F2A88X-D3H and my former
A8-5500/GA-F2A85X-D3H hardware causes random reboots or system hangs with no
outputs in the system logs.
The setting indeed enables turbo core.

Also, a simpler way of seeing the actual working frequency is loading the msr
module:

modprobe msr

Then running:

cpufreq-aperf

or 

cpufreq-aperf -o 

for a single poll.
both commands with root rights. This will show the actual frequency in Hz
(which sometimes is between the nominal p-states, or maybe the polling does
averages).

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). 

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). 4 threads
(compile) usually settled all cores at a stable ~3.7-3.8 GHz (temps up to 60C,
default cooler). These are values on the A8-6500 (3.5GHz nominal/4.1 GHz turbo
speed from which never exceeded 4.0 as long as i monitored it).

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