linux-kernel - Re: [PATCH 5/5] power: supply: bq27xxx: Correct supply status with current draw

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Message-ID: <20170531173207.GA10763@amd>
Date:   Wed, 31 May 2017 19:32:07 +0200
From:   Pavel Machek <pavel@....cz>
To:     Paul Kocialkowski <contact@...lk.fr>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pali Rohár <pali.rohar@...il.com>,
        "Andrew F . Davis" <afd@...com>,
        Sebastian Reichel <sre@...nel.org>,
        Chris Lapa <chris@...a.com.au>,
        Matt Ranostay <mranostay@...il.com>
Subject: Re: [PATCH 5/5] power: supply: bq27xxx: Correct supply status with
 current draw

Hi!

> > > The status reported directly by the battery controller is not always
> > > reliable and should be corrected based on the current draw information.
> > > 
> > > This implements such a correction with a dedicated function, called
> > > when retrieving the supply status.

> > > @@ -1182,6 +1196,8 @@ static int bq27xxx_battery_status(struct
> > > bq27xxx_device_info *di,
> > >  		else
> > >  			status = POWER_SUPPLY_STATUS_DISCHARGING;
> > >  	} else {
> > > +		curr = (int)((s16)curr) * 1000;
> > 
> > Umm.

As in "two casts in one expression -- too ugly to live".

> > > @@ -1190,6 +1206,18 @@ static int bq27xxx_battery_status(struct
> > > bq27xxx_device_info *di,
> > >  			status = POWER_SUPPLY_STATUS_CHARGING;
> > >  	}
> > >  
> > > +
> > > +	if (curr == 0 && status != POWER_SUPPLY_STATUS_NOT_CHARGING)
> > > +		status = POWER_SUPPLY_STATUS_FULL;
> > > +
> > > +	if (status == POWER_SUPPLY_STATUS_FULL) {
> > > +		/* Drawing or providing current when full */
> > > +		if (curr > 0)
> > > +			status = POWER_SUPPLY_STATUS_CHARGING;
> > > +		else if (curr < 0)
> > > +			status = POWER_SUPPLY_STATUS_DISCHARGING;
> > > +	}
> > 
> > Are you sure this works? On N900, we normally see small currents to/from
> > "full" battery.
> 
> In my case, this works perfectly and I am quite surprised of what you're
> describing. Is it the case when the battery has a PSU connected?

"PSU"? This is cellphone. It has USB connection and charges from that.

It has been charging for long while now, and current_now fluctuates
between 20706 and -2856. USB has limitted current, so I guess "draw
current from battery if we need more than USB can provide" is quite common.

pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
5355
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
5355
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
-4105
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
-4105
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
-7675
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
-5712
pavel@...0:~$ #screen on
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
4641
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
4641
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
37842
pavel@...0:~$ cat /sys/class/power_supply/bq27200-0/current_now
16600
pavel@...0:~$

> I guess I would consider this a hardware issue (leak currents) and we could
> definitely set some range (in device-tree) to distinguish between full + leak
> currents and bad reporting from the fuel gauge. That would work well in my case
> too.

I'd pass to userspace what the controller reports. Yes, I seldom see
"STATUS_FULL" but that may be a problem we need to track down.



       	  	 	     		 	      	    	    	 Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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