Messages in this thread Patch in this message | | | Date | Sat, 31 Oct 2009 11:03:01 +0100 | From | Krzysztof Helt <> | Subject | [PATCH] powernow-k6: set transition latency value so ondemand governor can be used |
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From: Krzysztof Helt <krzysztof.h1@wp.pl>
Set the transition latency to value smaller than CPUFREQ_ETERNAL so governors other than "performance" work (like the "ondemand" one).
The value is found in "AMD PowerNow! Technology Platform Design Guide for Embedded Processors" dated December 2000 (AMD doc #24267A). There is the answer to one of FAQs on page 40 which states that suggested complete transition period is 200 us.
Tested on K6-2+ CPU with K6-3 core (model 13, stepping 4).
Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl> --- This is the second version of the patch with added comment into the source code.
arch/x86/kernel/cpu/cpufreq/powernow-k6.c | 11 +++++++++-- 1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/cpufreq/powernow-k6.c b/arch/x86/kernel/cpu/cpufreq/powernow-k6.c index f10dea4..15f84a6 100644 --- a/arch/x86/kernel/cpu/cpufreq/powernow-k6.c +++ b/arch/x86/kernel/cpu/cpufreq/powernow-k6.c @@ -163,8 +163,15 @@ static int powernow_k6_cpu_init(struct cpufreq_policy *policy) clock_ratio[i].frequency = busfreq * f; } - /* cpuinfo and default policy values */ - policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL; + /* + * cpuinfo and default policy values + * + * The value is found in "AMD PowerNow! Technology Platform + * Design Guide for Embedded Processors" dated December 2000 + * (AMD doc #24267A). There is the answer to one of FAQs on page 40 + * which states that suggested complete transition period is 200 us. + */ + policy->cpuinfo.transition_latency = 200000; policy->cur = busfreq * max_multiplier; result = cpufreq_frequency_table_cpuinfo(policy, clock_ratio); -- 1.6.4
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