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Subject[PATCH] powernow-k6: set transition latency value so ondemand governor can be used
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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