On Sat, Apr 28, 2012 at 2:31 AM, Kevin Hilman <khilman@xxxxxx> wrote: > Hi Mark, > > Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> writes: > >> On Fri, Apr 27, 2012 at 11:09:10AM +0530, J, KEERTHY wrote: >> >>> Devfreq and cpufreq are related to dynamic frequency/voltage switching between >>> pre defined Operating Performance Points or the OPPs. Every OPP being >>> a voltage/frequency pair. Smartreflex is a different >>> power management technique. >> >> But presumably these things should integrate somehow - for example, >> should devfreq and cpufreq be providing inputs into what AVS is doing, >> and if so how? > > The way it is currently designed, cpufreq/devfreq/regulator layers don't > need to know about AVS. > > The higher-level layers only know about the "nominal" voltage. AVS > hardware does automatic, adaptive, micro-adjustments around that nominal > voltage, and these micro-adjustments are managed by the AVS hardware > sending commands to the PMIC. (specifically, on OMAP, the AVS sensors > provide inputs to the voltage processor (VP) which provide inputs to the > voltage controller (VC) which sends commands to the PMIC[1].) > > The driver proposed here is primarily for initializing the various > parameters/sensitivity/etc. of the AVS hardware, but the actual voltage > adjustments are done in hardware by VC/VP. > > The only thing the higher-level layers might potentially need to do to > enable/disable AVS around transitions (e.g. when changing OPP, AVS is > disabled before changing OPP and only re-enabled when the new nominal > voltage has been acheived.) > > On OMAP, we handle this inside the OMAP-specific voltage layer which is > called by the regulator framework, so even the regulators do not need > any knowledge of AVS. > > Kevin > > [1] Figure 3-76 in OMAP4430 ES2.1 Public TRM vAD provides a > detailed diagram: > http://www.ti.com/pdfs/wtbu/OMAP4430_ES2.x_PUBLIC_TRM_vAD.zip Thanks for the detailed answer Kevin. -- Regards and Thanks, Keerthy _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/linux-pm
