1a3c98b8bSMyungJoo Hamconfig ARCH_HAS_DEVFREQ 2a3c98b8bSMyungJoo Ham bool 3a3c98b8bSMyungJoo Ham depends on ARCH_HAS_OPP 4a3c98b8bSMyungJoo Ham help 5a3c98b8bSMyungJoo Ham Denotes that the architecture supports DEVFREQ. If the architecture 6a3c98b8bSMyungJoo Ham supports multiple OPP entries per device and the frequency of the 7a3c98b8bSMyungJoo Ham devices with OPPs may be altered dynamically, the architecture 8a3c98b8bSMyungJoo Ham supports DEVFREQ. 9a3c98b8bSMyungJoo Ham 10a3c98b8bSMyungJoo Hammenuconfig PM_DEVFREQ 11a3c98b8bSMyungJoo Ham bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support" 12a3c98b8bSMyungJoo Ham depends on PM_OPP && ARCH_HAS_DEVFREQ 13a3c98b8bSMyungJoo Ham help 14a3c98b8bSMyungJoo Ham With OPP support, a device may have a list of frequencies and 15a3c98b8bSMyungJoo Ham voltages available. DEVFREQ, a generic DVFS framework can be 16a3c98b8bSMyungJoo Ham registered for a device with OPP support in order to let the 17a3c98b8bSMyungJoo Ham governor provided to DEVFREQ choose an operating frequency 18a3c98b8bSMyungJoo Ham based on the OPP's list and the policy given with DEVFREQ. 19a3c98b8bSMyungJoo Ham 20a3c98b8bSMyungJoo Ham Each device may have its own governor and policy. DEVFREQ can 21a3c98b8bSMyungJoo Ham reevaluate the device state periodically and/or based on the 22a3c98b8bSMyungJoo Ham OPP list changes (each frequency/voltage pair in OPP may be 23a3c98b8bSMyungJoo Ham disabled or enabled). 24a3c98b8bSMyungJoo Ham 25a3c98b8bSMyungJoo Ham Like some CPUs with CPUFREQ, a device may have multiple clocks. 26a3c98b8bSMyungJoo Ham However, because the clock frequencies of a single device are 27a3c98b8bSMyungJoo Ham determined by the single device's state, an instance of DEVFREQ 28a3c98b8bSMyungJoo Ham is attached to a single device and returns a "representative" 29a3c98b8bSMyungJoo Ham clock frequency from the OPP of the device, which is also attached 30a3c98b8bSMyungJoo Ham to a device by 1-to-1. The device registering DEVFREQ takes the 31a3c98b8bSMyungJoo Ham responsiblity to "interpret" the frequency listed in OPP and 32a3c98b8bSMyungJoo Ham to set its every clock accordingly with the "target" callback 33a3c98b8bSMyungJoo Ham given to DEVFREQ. 34a3c98b8bSMyungJoo Ham 35a3c98b8bSMyungJoo Hamif PM_DEVFREQ 36a3c98b8bSMyungJoo Ham 37a3c98b8bSMyungJoo Hamcomment "DEVFREQ Drivers" 38a3c98b8bSMyungJoo Ham 39a3c98b8bSMyungJoo Hamendif # PM_DEVFREQ 40