Yong, Idea of defining various C states is to get maximum power savings both active and inactive usecases. C states you defined below are definitely good as a starting point. May be you can define more C states by adding more granularity depending on what are controlled as part of CPUIdle. Eg: In OMAP, we have defined C states primarily based on MPU and Core States as they are controlled in CPUIdle. MPU supports ON, INACTIVE, RETENTION and OF state and similarly the Core. So C states are defined based on various MPU and Core state combinations (MPU INACTIVE - CORE ACTIVE, MPU RET - CORE RET etc).
Vishwa On Mon, Jan 31, 2011 at 3:17 PM, Yong Shen <yong.s...@linaro.org> wrote: > Hi there, > I am trying to implement cpuidle driver for imx51, and for better > understanding how various c-state map to ARM soc, > I would like to get some comments. > First of all, we basically have 3 major state for imx51, which are defined > in specification of the soc. Like: > RUN - Core is active, clocks are on, the peripheral modules required are > active. SW can close > clocks of modules that are not in use. In addition CCM can enable power > gating for the modules described above. > WAIT - Core is disabled and clock gated, bus clocks to peripherals can be on > as required. PG [power gating] and > SRPG[state retention PG] can be applied to Cortex_A8 and the different > blocks as described on the section above. > STOP - Core is disabled, peripherals are disabled, bus clocks are off, PLLs > off. PG and SRPG can > be applied to Cortex_A8 and the different blocks as described on the section > above. > Naturely, I think the maping can be: > RUN - c0 > WAIT - c1 > STOP - c2 > Or, if possible, some extra states can be assert into each c-state to get > c3, c4.... > Since other SOCs, like omap or samsung's chip, already have cpuidle driver, > I would like to especially compare imx51 with those. > thanks > Yong _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
