From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dirk Behme Subject: Re: Gumstix Overo Low Power Standby? Date: Wed, 27 May 2009 20:59:26 +0200 Message-ID: <4A1D8D8E.9070501@googlemail.com> References: <87ws8bog2c.fsf@deeprootsystems.com> <87iqjvoe0q.fsf@deeprootsystems.com> <249CF2F5-CA30-49BE-8524-B81AEC4D42A5@cornell.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-bw0-f222.google.com ([209.85.218.222]:51198 "EHLO mail-bw0-f222.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758840AbZE0S7i (ORCPT ); Wed, 27 May 2009 14:59:38 -0400 Received: by bwz22 with SMTP id 22so4900338bwz.37 for ; Wed, 27 May 2009 11:59:39 -0700 (PDT) In-Reply-To: <249CF2F5-CA30-49BE-8524-B81AEC4D42A5@cornell.edu> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Blazej Kot Cc: linux-omap@vger.kernel.org, Kevin Hilman Blazej Kot wrote: > > On May 20, 2009, at 1:55 PM, Kevin Hilman wrote: > >> Kevin Hilman writes: >> >>> Blazej Kot writes: >>> >>>> I have been working with the linux-pm kernel on the Gumstix Overo, >>>> seeing how low it's power consumption can go, both during the cpu "on" >>>> and especially while the CPU is suspended. Thus far, I've had some >>>> disappointing results, the best I could get is about 500mW while on, >>>> and 250mW while suspended (ie by running "echo mem > /sys/power/ >>>> state"). I am led to believe that the OMAP processor is capable of >>>> much lower power consumption during standby. >>>> >>>> I am wondering if anybody in the gumstix community is looking into the >>>> software support for very-low-power modes on the overo. If so, I am >>>> wondering what the lowest power levels are which you have reached >>>> during standby are. >>>> >>>> I have seen this: >>>> >>>> http://markmail.org/message/ge5hec5f5asp7a67#query:omap%20linux >>>> %2080%20ma+page:1+mid:t2erlwweknakm767+state:results >>>> >>>> Which seems to indicate the lowest power reached is 80mA at 3.3V -> >>>> 0.264 W, which is about what I'm seeing. Is it really true that the >>>> overo draws a quarter of a watt when doing absolutely nothing? >>> >>> There are lots of factors involved. >>> >>> The current OMAP PM branch is focused on minimizing power consumed by >>> the OMAP SoC itself. However, there are lots of other things on-board >>> (audio codecs, regulators, WiFi chipsets etc.) that can consume power >>> that we may not be currently managing in the omap kernel. >>> >>> I don't have an Overo so am not familiar with all the on board >>> peripherals, but you should probably do some experiments where you >>> can put all the on-board devices into low-power/off states and >>> run some experiments as well. >>> >>> In the case of the Beagle results you referenced, I'm pretty sure it >>> is something on board that is drawing the ~80mA and not on-chip. I >>> assume this because setting the OMAP to use OFF-mode in suspend or >>> idle results in the drop of a few mA reflecting an expected drop in >>> power consumed by OMAP itself, but still leaving lots of power >>> consumed. >>> >>> For example, testing today's PM branch on Beagle gives me roughly the >>> same numbers as the post you referenced, but slightly better: >>> >>> - boot idle: 323 mA >>> >>> - screen blank: 216 mA >>> # echo 3 > /sys/class/graphics/fb0/blank >>> >>> - suspend (OMAP retention): 75 mA >>> # echo mem > /sys/power/state >>> >>> - sleep-while-idle: 75 mA - this same power state as suspend, >>> but happens in idle >>> # echo 1 > /sys/power/sleep_while_idle >>> >>> - suspend (OMAP off): 72 mA >>> # echo 1 > /sys/power/enable_off_mode >>> # echo 1 > /sys/power/voltage_off_while_idle >>> >>> Ultimitately the answer is that more work needs to be done with the >>> using the regulator framework and/or the drivers for the on-chip >>> peripherals to be sure they can be powered off when needed. >>> >> >> After digging a little more in the beagle forums, someone has already >> done the work to confirm that it is indeed board level design and >> issues that are drawing the rest of the power on Beagle. >> >> There's a thread[1] in the beagleboard list about how to get down to >> 8mW power on Beagle, but it does require hardware changes. This >> should shed some light on the types of things you'd probably have >> to do for Overo. >> >> Kevin >> >> [1] >> http://groups.google.com/group/beagleboard/browse_thread/thread/197a8ef6b46cc828/6e98db4cbe2cebaa?# >> > > > Thanks for that, it is an interesting link. I have now reached the new > low of around 170mW (at 3.28V), but this is high. I basically used the > TWL (PMC) scripts in the linked post, and also turned off the U6 chip on > the gumstix, which is the USB PHY layer driver. > > Also, I noticed that my systems becomes unusable after suspending for > more than abut a minute, and it will not wake from sleep. I will try to > troubleshot and narrow this down. I think to remember there was some discussion about SDRAM self refresh. Look for thread "OMAP3: PM: SDRC: ensure mux of SDRC clock enable pins for self-refresh" and http://www.sakoman.net/cgi-bin/gitweb.cgi?p=u-boot-omap3.git;a=commit;h=4025cfbde3611b14c0d4831a5524e5e061128e30 Just guessing, though. Dirk > I am wondering, is there anyone out there working on PM issues on the > Gumstix? Perhaps if there are some gumstix company people here they can > answer what their status is. I will ask around on the gumstix emailing > list also. > > thanks, > Blazej > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >