From dfde5d62ed9b28b0bda676c16e8cb635df244ef2 Mon Sep 17 00:00:00 2001 From: Venkatesh Pallipadi Date: Tue, 3 Oct 2006 12:38:45 -0700 Subject: [CPUFREQ][8/8] acpi-cpufreq: Add support for freq feedback from hardware MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Enable ondemand governor and acpi-cpufreq to use IA32_APERF and IA32_MPERF MSR to get active frequency feedback for the last sampling interval. This will make ondemand take right frequency decisions when hardware coordination of frequency is going on. Without APERF/MPERF, ondemand can take wrong decision at times due to underlying hardware coordination or TM2. Example: * CPU 0 and CPU 1 are hardware cooridnated. * CPU 1 running at highest frequency. * CPU 0 was running at highest freq. Now ondemand reduces it to some intermediate frequency based on utilization. * Due to underlying hardware coordination with other CPU 1, CPU 0 continues to run at highest frequency (as long as other CPU is at highest). * When ondemand samples CPU 0 again next time, without actual frequency feedback from APERF/MPERF, it will think that previous frequency change was successful and can go to wrong target frequency. This is because it thinks that utilization it has got this sampling interval is when running at intermediate frequency, rather than actual highest frequency. More information about IA32_APERF IA32_MPERF MSR: Refer to IA-32 Intel® Architecture Software Developer's Manual at http://developer.intel.com Signed-off-by: Venkatesh Pallipadi Signed-off-by: Dave Jones --- drivers/cpufreq/cpufreq.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) (limited to 'drivers/cpufreq/cpufreq.c') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 86e69b7f912..56c433e64d5 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -1274,6 +1274,26 @@ int cpufreq_driver_target(struct cpufreq_policy *policy, } EXPORT_SYMBOL_GPL(cpufreq_driver_target); +int cpufreq_driver_getavg(struct cpufreq_policy *policy) +{ + int ret = 0; + + policy = cpufreq_cpu_get(policy->cpu); + if (!policy) + return -EINVAL; + + mutex_lock(&policy->lock); + + if (cpu_online(policy->cpu) && cpufreq_driver->getavg) + ret = cpufreq_driver->getavg(policy->cpu); + + mutex_unlock(&policy->lock); + + cpufreq_cpu_put(policy); + return ret; +} +EXPORT_SYMBOL_GPL(cpufreq_driver_getavg); + /* * Locking: Must be called with the lock_cpu_hotplug() lock held * when "event" is CPUFREQ_GOV_LIMITS -- cgit v1.2.3