linux-kernel - Re: [PATCH] sbs-battery: fix power status when battery is dry

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Date:	Tue, 29 Mar 2016 09:52:33 +0800
From:	YH Huang <yh.huang@...iatek.com>
To:	Rhyland Klein <rklein@...dia.com>
CC:	Daniel Kurtz <djkurtz@...omium.org>, <linux-pm@...r.kernel.org>,
	"Dmitry Eremin-Solenikov" <dbaryshkov@...il.com>,
	Sebastian Reichel <sre@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@...ts.infradead.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] sbs-battery: fix power status when battery is dry

On Mon, 2016-03-28 at 11:57 -0400, Rhyland Klein wrote:
> On 3/28/2016 6:05 AM, Daniel Kurtz wrote:
> > +Rhyland Klein who original wrote this code...
> > 
> > On Mon, Mar 28, 2016 at 10:32 AM, YH Huang <yh.huang@...iatek.com> wrote:
> >>
> >> On Fri, 2016-03-25 at 11:06 +0800, Daniel Kurtz wrote:
> >>> On Thu, Mar 24, 2016 at 2:43 PM, YH Huang <yh.huang@...iatek.com> wrote:
> >>>>
> >>>> Hi Daniel,
> >>>>
> >>>> On Thu, 2016-03-24 at 12:01 +0800, Daniel Kurtz wrote:
> >>>>> Hi YH,
> >>>>>
> >>>>> On Wed, Mar 23, 2016 at 5:53 PM, YH Huang <yh.huang@...iatek.com> wrote:
> >>>>>> When the battery is dry and BATTERY_FULL_DISCHARGED is set,
> >>>>>> we should check BATTERY_DISCHARGING to decide the power status.
> >>>>>> If BATTERY_DISCHARGING is set, the power status is not charging.
> >>>>>> Or the power status should be charging.
> >>>>>>
> >>>>>> Signed-off-by: YH Huang <yh.huang@...iatek.com>
> >>>>>> ---
> >>>>>>  drivers/power/sbs-battery.c |   22 ++++++++++++----------
> >>>>>>  1 file changed, 12 insertions(+), 10 deletions(-)
> >>>>>>
> >>>>>> diff --git a/drivers/power/sbs-battery.c b/drivers/power/sbs-battery.c
> >>>>>> index d6226d6..d86db0e 100644
> >>>>>> --- a/drivers/power/sbs-battery.c
> >>>>>> +++ b/drivers/power/sbs-battery.c
> >>>>>> @@ -382,11 +382,12 @@ static int sbs_get_battery_property(struct i2c_client *client,
> >>>>>>
> >>>>>>                 if (ret & BATTERY_FULL_CHARGED)
> >>>>>>                         val->intval = POWER_SUPPLY_STATUS_FULL;
> >>>>>> -               else if (ret & BATTERY_FULL_DISCHARGED)
> >>>>>> -                       val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
> >>>>>> -               else if (ret & BATTERY_DISCHARGING)
> >>>>>> -                       val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
> >>>>>> -               else
> >>>>>> +               else if (ret & BATTERY_DISCHARGING) {
> >>>>>> +                       if (ret & BATTERY_FULL_DISCHARGED)
> >>>>>> +                               val->intval = POWER_SUPPLY_STATUS_NOT_CHARGING;
> >>>>>> +                       else
> >>>>>> +                               val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
> >>>>>> +               } else
> >>>>>
> >>>>>
> >>>>> I think (BATTERY_DISCHARGING && BATTERY_FULL_DISCHARGED) is still
> >>>>> POWER_SUPPLY_STATUS_DISCHARGING.
> >>>>> So, let's just report what the battery says and do:
> >>>>>
> >>>>>                else if (ret & BATTERY_DISCHARGING)
> >>>>>                                val->intval = POWER_SUPPLY_STATUS_DISCHARGING;
> >>>>>
> >>>> So we just ignore the special situation (BATTERY_DISCHARGING &&
> >>>> BATTERY_FULL_DISCHARGED).
> >>>> Isn't POWER_SUPPLY_STATUS_NOT_CHARGING a useful information?
> >>>
> >>> The battery is discharging.  The fact that it is also reporting that
> >>> it is already "discharged" just seems premature.   I would expect to
> >>> only see NOT_CHARGING if completely discharged *and* not discharging.
> >>
> >> I check the "Smart Battery Data Specification Revision 1.1".
> >> And there are some words about FULLY_DISCHARGED.
> >> "Discharge should be stopped soon."
> >> "This status bit may be set prior to the
> >> ‘TERMINATE_DISCHARGE_ALARM’ as an early or first level warning of end of
> >> battery charge."
> >> It looks like the FULLY_DISCHARGED status is used to announce the
> >> warning of battery charge and it is still discharging if there is no one
> >> takes care of it.
> 
> 
> The only difference I see in the patch above is that in the case where
> DISCHARGING isn't set, it won't check FULL_DISCHARGE. Nothing seems to
> be changed in the case where FULL_DISCHARGE & DISCHARGING are set.

If battery is dry(FULLY_DISCHARGED) and is charging(No
BATTERY_DISCHARGING) by AC at the same time,
I think it is better to mark as POWER_SUPPLY_STATUS_CHARGING.
Is this right?

> 
> I think in the case that both flags are set, it makes sense to
> prioritize the FULL_DISCHARGE, since as quote above actually starts with
> "FULLY_DISCHARGED bit is set when the Smart Battery determines that it
> has supplied all the charge it can." I think at the point where both
> statuses are reported, the fact that it is still DISCHARGING doesn't
> matter. The code as is handles this in that manner, so I don't see a
> need to change it.
> 
> -rhyland
> 
>