diff options
Diffstat (limited to 'drivers/devfreq')
| -rw-r--r-- | drivers/devfreq/Kconfig | 41 |
1 files changed, 17 insertions, 24 deletions
diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig index 643b055ed3c..8f049103708 100644 --- a/drivers/devfreq/Kconfig +++ b/drivers/devfreq/Kconfig @@ -1,36 +1,29 @@ -config ARCH_HAS_DEVFREQ - bool - depends on ARCH_HAS_OPP - help - Denotes that the architecture supports DEVFREQ. If the architecture - supports multiple OPP entries per device and the frequency of the - devices with OPPs may be altered dynamically, the architecture - supports DEVFREQ. - menuconfig PM_DEVFREQ bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support" - depends on PM_OPP && ARCH_HAS_DEVFREQ help - With OPP support, a device may have a list of frequencies and - voltages available. DEVFREQ, a generic DVFS framework can be - registered for a device with OPP support in order to let the - governor provided to DEVFREQ choose an operating frequency - based on the OPP's list and the policy given with DEVFREQ. + A device may have a list of frequencies and voltages available. + devfreq, a generic DVFS framework can be registered for a device + in order to let the governor provided to devfreq choose an + operating frequency based on the device driver's policy. - Each device may have its own governor and policy. DEVFREQ can + Each device may have its own governor and policy. Devfreq can reevaluate the device state periodically and/or based on the - OPP list changes (each frequency/voltage pair in OPP may be - disabled or enabled). + notification to "nb", a notifier block, of devfreq. - Like some CPUs with CPUFREQ, a device may have multiple clocks. + Like some CPUs with CPUfreq, a device may have multiple clocks. However, because the clock frequencies of a single device are - determined by the single device's state, an instance of DEVFREQ + determined by the single device's state, an instance of devfreq is attached to a single device and returns a "representative" - clock frequency from the OPP of the device, which is also attached - to a device by 1-to-1. The device registering DEVFREQ takes the - responsiblity to "interpret" the frequency listed in OPP and + clock frequency of the device, which is also attached + to a device by 1-to-1. The device registering devfreq takes the + responsiblity to "interpret" the representative frequency and to set its every clock accordingly with the "target" callback - given to DEVFREQ. + given to devfreq. + + When OPP is used with the devfreq device, it is recommended to + register devfreq's nb to the OPP's notifier head. If OPP is + used with the devfreq device, you may use OPP helper + functions defined in devfreq.h. if PM_DEVFREQ |