Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753105AbZLMNY2 (ORCPT ); Sun, 13 Dec 2009 08:24:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751027AbZLMNY1 (ORCPT ); Sun, 13 Dec 2009 08:24:27 -0500 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:45107 "HELO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750852AbZLMNY0 (ORCPT ); Sun, 13 Dec 2009 08:24:26 -0500 Date: Sun, 13 Dec 2009 14:24:14 +0100 From: Pavel Machek To: Mark Brown Cc: Linus Walleij , cbou@mail.ru, dwmw2@infradead.org, LKML , linux-embedded@vger.kernel.org, Brian Swetland , rpurdie@rpsys.net, lenz@cs.wisc.edu, Dirk@Opfer-Online.de, arminlitzel@web.de, Cyril Hrubis , thommycheck@gmail.com, linux-arm-kernel , dbaryshkov@gmail.com, omegamoon@gmail.com, eric.y.miao@gmail.com, utx@penguin.cz, zaurus-devel@www.linuxtogo.org Subject: Re: [POWER] battery calibration parameters from sysfs Message-ID: <20091213132413.GB1437@ucw.cz> References: <20091204104930.GA28625@sirena.org.uk> <20091207114825.GA26965@rakim.wolfsonmicro.main> <20091207165628.GA24981@rakim.wolfsonmicro.main> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091207165628.GA24981@rakim.wolfsonmicro.main> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6257 Lines: 170 Hi! > > If you browse down to line 275 you can see it parse the sysfs > > attribute "capacity", then this propagates up to the battery > > status indicator on *all* Android phones out there. So if > > you want to run Android unmodified, this is what you need to > > provide. They are effectively using the power sysfs as > > their hardware abstraction layer in this case. > > Oh dear. Using the power sysfs as the hardware abstraction seems > perfectly reasonable but assuming that a given battery driver is going > to have this level of information doesn't match up with an awful lot of > actual charger hardware. My main concern here is that battery > performance monitoring has no pressing need to be in kernel and that > pushing it into the kernel creates a barrier to implementing more > advanced schemes in userspace, which is especially serious given how > involved this needs to be in order to be accurate. Well, kernel provides /proc/apm emulation and many systems still rely on it. So it would be nice to provide something halfway-decent there. Plus you need to shutdown/suspend machine on battery critical. That has to be in kernel and already needs those tricky parts. (Sharp got it wrong in collie kernel, and you get 5hours instead of 10 with old battery :-((). > I'm not sure how familiar you are with the issues surrounding trying to > do a voltage to charge mapping for a battery but it's much more complex > than a simple table if you want to get it accurate. There's a lot > of Well... current zaurus kernels use _huge_ table that maps voltage to battery %... and that table is linear function :-(. Do you have some papers on that? > dependence on particular operating conditions and things do change as > the batteries age. There are systems out there that do the work > required to gather the information in hardware and it's definitely good > to report the information from them but that doesn't mean it's a good > idea to try to synthesise the information for other systems. So... on zaurus I plan to: 1) provide better voltage -- %age map 2) estimate current 3) estimate internal battery resistance as constant 4) estimate internal battery volltage using ohm's law and base %age estmate on that. Now... I realize that internal resistance depends on charge left. Nasty but probably can be ignored. Then it depends on temperature. Does anyone have better idea how? Then... I need a way to measure internal resistance. I know it is in 200mOhm to 400mOhm range, on my device. Is there easy way to measure it more accurately? Pavel #!/bin/bash # # Copyright 2009 Pavel Machek , GPLv2 # getval() { SETTLETIME=5 echo Run this on idle, unplugged system, with expansion cards echo removed and backlight enabled echo echo 1 > /sys/class/backlight/corgi?bl/brightness echo Backlight 1, waiting for power to settle sleep $SETTLETIME VBMIN=`cat /sys/class/power*/*battery/voltage_now` VBMIN=$[$VBMIN/1000] echo Voltage = $VBMIN mV echo echo 47 > /sys/class/backlight/corgi?bl/brightness echo Backlight 47, waiting for power to settle sleep $SETTLETIME VBMAX=`cat /sys/class/power*/*battery/voltage_now` VBMAX=$[$VBMAX/1000] echo Voltage = $VBMAX mV echo 1 > /sys/class/backlight/corgi?bl/brightness } fake1() { # Very old 1000mAh battery from collie: 703 mOhm VBMIN=3638 VBMAX=3543 } fake2() { # Old 2000mAh battery, nearly charged, 4C: 274 mOhm VBMIN=3732 VBMAX=3695 } fake3() { # Same old 2000mAh battery, nearly charged, 4C: 140 mOhm # temp: 155. VBMIN=3714 VBMAX=3695 # Next try: temp 151 -- little warmer: 422 mOhm. # Next try: temp 151 -- little warmer: 1266 mOhm. # Next try: temp 148 -- getting warmer: 281 mOhm. # Next try: temp 148 -- getting warmer, full load: 422 mOhm. # Next try: temp 148 -- getting warmer, full load: 140 mOhm. # Next try: temp 148 -- getting warmer, full load: 422 mOhm. # Next try: temp 138 -- getting warmer, full load: 422 mOhm. # Next try: temp 139 -- getting warmer, full load: 422 mOhm. # Next try: temp 136 -- getting warmer, full load: 562 mOhm. # Next try: temp 132 -- getting warmer, full load: 703 mOhm. # Next try: temp 132 -- getting warmer, full load: 281 mOhm. # Next try: temp 134 -- getting warmer, full load: 281 mOhm. # Next try: temp 134 -- getting warmer, full load: 562 mOhm. # Next try: temp 129 -- getting warmer, full load: 562 mOhm. # hugh, I''m getting n*140, wtf? # ...voltmeters have sensitivity limits... # temp 118 -- metro, venku zima -- full load: 281 mOhm. # temp 118 -- metro, venku zima, baterie poloprazdna -- full load: 281 mOhm. # temp 120 -- metro, venku zima, baterie poloprazdna -- full load: 281 mOhm. # temp 120 -- metro, venku zima, baterie poloprazdna -- full load: 281 mOhm. # temp 120 -- metro, venku zima, baterie poloprazdna -- full load: 414 mOhm. # temp 120 -- metro, venku zima, baterie poloprazdna -- full load: 555 mOhm. # temp 120 -- metro, venku zima, baterie poloprazdna -- full load: 422 mOhm. # temp 124 -- metro, venku zima, baterie poloprazdna -- full load: 422 mOhm. # temp 127 -- metro, venku zima, baterie poloprazdna -- full load: 422 mOhm. } getval #fake1 BLDIFF=135 echo Assuming $BLDIFF mA difference echo $VBMIN $VBMAX $BLDIFF # With RESIST in mOhm # VINSIDE = VBMIN + RESIST * BASECURRENT / 1000 # VINSIDE = VBMAX + RESIST * (BASECURRENT + BLDIFF) / 1000 # Therefore # RESIST = 1000*(VBMIN-VBMAX)/BLDIFF RESIST=$[(1000*($VBMIN-$VBMAX))/$BLDIFF] echo Resistance is $RESIST mOhm BASECURRENT=280 echo This should be equal: echo During low backlight $[$VBMIN + ($RESIST * $BASECURRENT) / 1000] mV echo During high backlight $[$VBMAX + ($RESIST * ($BASECURRENT + $BLDIFF)) / 1000] mV -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/