> -----Original Message----- > From: Paul Walmsley [mailto:paul@xxxxxxxxx] > Sent: Tuesday, February 01, 2011 4:44 AM > To: Santosh Shilimkar > Cc: linux-omap@xxxxxxxxxxxxxxx; khilman@xxxxxx; b-cousson@xxxxxx; > rnayak@xxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/6] omap4: powerdomain: Add supported INACTIVE > power state > > Hello Santosh, > > On Fri, 28 Jan 2011, Santosh Shilimkar wrote: > > > On OMAP4, one can explicitly program INACTIVE as the power state > of > > the logic area inside the power domain. Techincally PD state > programmed > > to ON and if all the clock domains within the PD are idled, is > equivalent > > tp PD programmed to INACTIVE and all the clock domains within the > PD are > > idled. There won't be any power difference in above two. > > > > Since the CPUIDLE C-states explicitly make use of INACTIVE as a PD > > targeted state and also there is some additional latancy involved > > with PD INACTIVE vs PD ON, it's better to support it as an explcit > > PD state. > > > > This patch adds the support to allow explicit PD INACTIVE > > programming if supported. > > What does the hardware do when the powerdomain is programmed to > INACTIVE? > Does it actually force the clockdomains idle? > No. It doesn't force it. The power domain to hit INACTIVE, the clockdomain within the power domain needs to idle and it is still a prerequisite. With INACTIVE being programmed, we could issue a sleep transition. PD_ON: No power transition, only clocks are gated. Power domain stays ON. PD_INA: Power domain transitions to INACTIVE state. All logic and memory stay powered. This state allows for a voltage sleep transition. Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
