diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/cpu-freq/governors.txt | 27 | ||||
| -rw-r--r-- | Documentation/power/opp.txt | 2 |
2 files changed, 29 insertions, 0 deletions
diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index 1eebdbf..c167a21 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -268,6 +268,33 @@ boostpulse_duration: Length of time to hold CPU speed at hispeed_freq on a write to boostpulse, before allowing speed to drop according to load as usual. Default is 80000 uS. +2.7 Hotplug +----------- + +The CPUfreq governor "hotplug" operates similary to "ondemand" and +"conservative". It's decisions are based primarily on CPU load. Like +"ondemand" the "hotplug" governor will ramp up to the highest frequency +once the run-time tunable "up_threshold" parameter is crossed. Like +"conservative", the "hotplug" governor exports a "down_threshold" +parameter that is also tunable at run-time. When the "down_threshold" +is crossed the CPU transitions to the next lowest frequency in the +CPUfreq frequency table instead of decrementing the frequency based on a +percentage of maximum load. + +The main reason "hotplug" governor exists is for architectures requiring +that only the master CPU be online in order to hit low-power states +(C-states). OMAP4 is one such example of this. The "hotplug" governor +is also helpful in reducing thermal output in devices with tight thermal +constraints. + +Auxillary CPUs are onlined/offline based on CPU load, but the decision +to do so is made after averaging several sampling windows. This is to +reduce CPU hotplug "thrashing", which can be caused by normal system +entropy and leads to lots of spurious plug-in and plug-out transitions. +The number of sampling periods averaged together is tunable via the +"hotplug_in_sampling_periods" and "hotplug_out_sampling_periods" +run-time tunable parameters. + 3. The Governor Interface in the CPUfreq Core ============================================= diff --git a/Documentation/power/opp.txt b/Documentation/power/opp.txt index 5ae70a12..3035d00 100644 --- a/Documentation/power/opp.txt +++ b/Documentation/power/opp.txt @@ -321,6 +321,8 @@ opp_init_cpufreq_table - cpufreq framework typically is initialized with addition to CONFIG_PM as power management feature is required to dynamically scale voltage and frequency in a system. +opp_free_cpufreq_table - Free up the table allocated by opp_init_cpufreq_table + 7. Data Structures ================== Typically an SoC contains multiple voltage domains which are variable. Each |