Hi, On Wed, Mar 16, 2011 at 8:31 PM, Marshall Crocker <maroc81@xxxxxxxxx> wrote: > Hi all, > > I have a few questions about PM functionality I would be grateful if > someone could answer. > > I'm trying to reduce power on a gumstix overo COM with the latest > 2.6.38 pm kernel branch up and running, I've enabled sleep while idle > and "off" mode along with serial timeouts and I do in fact see a major > drop in power consumption when it hits idle/off mode. > > 1) Should the "mem" power state reduce power further? Or does that > simply force the omap into the same states achieved by sleep while > idle and off mode enabled? I'm not seeing any less power in "mem" > state versus idle/off state. No the resulting power savings are the same. 'mem' is just a forced suspend state while idle tries to reach the lowest power state dynamically. > 2) I saw from earlier emails that DVFS is currently disabled. Would > I see any power additional power savings with DVFS? Obviously, power > would be reduced if I ran a governor such as on demand so that waking > up from idle doesn't use full speed unless needed. Are there any > other benefits? Should I wait for DVFS to be merged back in to PM or > apply the patches that are waiting for approval? The patches are not yet merged in. Of course you can apply them locally. > 3) Are peripherals such as SPI, I2C, etc disabled when in idle/off > mode? I'm coming from a microcontroller background where disabling > unused peripherals can save power. Is that true for the omap? Yes all peripherals are dynamically put in the lowest power mode possible. > 4) Any additional power saving tips? I have PHY_PWR_CTRL disabled and > I assume there are more steps I can take to disable unneeded functions > on the PMIC but I have not gotten far yet. One thing I can think of is to verify that the power supplies and clocks external to the OMAP are actually cut off in off mode. The power IC scripts patches are needed for this [1]. [1] http://marc.info/?l=linux-omap&m=129907267322294&w=2 Please note that the PM-enabled git trees for OMAP are found at http://git.kernel.org/?p=linux/kernel/git/khilman/linux-omap-pm.git;a=summary and http://git.kernel.org/?p=linux/kernel/git/tmlind/linux-omap-2.6.git;a=summary. > > Thanks for any help! > > Marshall Regards, Jean > -- > 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 > -- 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
