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SubjectAMD Mobile Semprons (3500+, 3600+,...) break with nohz and highres enabled

we got a bit further, Evgeny was able to get C-states working with
"nohz=off highres=off" boot parameters.

A short summary what has been found out that far:
- apic timer breaks on C2 or deeper
- noapictimer workaround helps to come a bit further, but results in sever
other errors (see comment #13)
- "nohz=off highres=off" works (tested on and SUSE kernels)
- processor.max_cstate=1 works
- This affects AMD Mobile Semprons (at least 3500+ and 3600+)

The output of /proc/acp/processor/*/power without highres/nohz
looks promising:
C1: type[C1] promotion[C2] demotion[--] latency[000]
usage[00000030] duration[00000000000000000000]
C2: type[C2] promotion[C3] demotion[C1] latency[005]
usage[00002135] duration[00000000000011279621]
*C3: type[C3] promotion[--] demotion[C2] latency[020]
usage[00034222] duration[00000000000228307174]

Also see bug:
and some posts from Richard on the linux-acpi list.

This seem to be a mainline kernel regression since the nohz/highres
patches have been added.
I do not own such a machine myself (Richard, Evgeny, Uli (and Anvin?)
have such a machine and already helped to come that far).

Also the highres/nohz parts are a dark area to me... Any pointer how to
debug (or debug patches or patches to test), where to look at, etc. is
very much appreciated.



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