x86, cpufreq: fix Speedfreq-SMI call that clobbers ECX

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I have found that using SMI to change the cpu's frequency on my DELL
Latitude L400 clobbers the ECX register in speedstep_set_state, causing
unneccessary retries because the "state" variable has changed silently (GCC
assumes it is still present in ECX).

play safe and avoid gcc caching any register across IO port accesses
that trigger SMIs.

Signed-off by: <Stephan.Diestelhorst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

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Stephan Diestelhorst 2008-03-10 16:05:41 +01:00 • committed by Ingo Molnar

parent 475613b9e3

commit c6e8256a7b

1 changed files with 24 additions and 15 deletions

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arch/x86/kernel/cpu/cpufreq/speedstep-smi.c

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