linux-kernel - Re: [RFC PATCH v2 1/5] dt-bindings: battry: add new battery parameters

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Message-ID: <58877fefa9e4792779284575e9f0aa561d646c2e.camel@fi.rohmeurope.com>
Date:   Thu, 20 Feb 2020 06:39:46 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "mazziesaccount@...il.com" <mazziesaccount@...il.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linus.walleij@...aro.org" <linus.walleij@...aro.org>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "Mutanen, Mikko" <Mikko.Mutanen@...rohmeurope.com>,
        "sre@...nel.org" <sre@...nel.org>,
        "Laine, Markus" <Markus.Laine@...rohmeurope.com>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH v2 1/5] dt-bindings: battry: add new battery
 parameters

Hello Rob,

On Wed, 2020-02-19 at 13:57 -0600, Rob Herring wrote:
> On Fri, Feb 14, 2020 at 09:30:05AM +0200, Matti Vaittinen wrote:
> > Add:
> > 
> >  - tricklecharge-current-microamp:
> > 
> > Some chargers have 3 charging stages. First one when battery is
> > almost
> > empty is often called as trickle-charge. Last state when battery
> > has been
> > "woken up" is usually called as fast-charge. In addition to this
> > some
> > chargers have a 'middle state' which ROHM BD99954 data-sheet
> > describes as
> > pre-charge. Some batteries can benefit from this 3-phase charging
> > [citation needed].
> 
> For car batteries at least, trickle charge is to keep battery full.
> But 
> maybe in that context, it would be 'charge-term-current-microamp'.
> 
> I'm just concerned that we end up with multiple properties that mean
> the 
> same thing. I think you're okay here.

While I was doing this I took a quick look in few other binding docs
under power/supply. Unfortunately my knowledge about batteries and
chargers is really limited - but I had a feeling that we already now
have bunch of vendor specific properties for same things. So I actually
hope that adding generic ones will decrease the birth rate of vendor
specific ones ;)

> > Introduce tricklecharge-current-microamp so that batteries can give
> > charging current limit for all three states.
> > 
> >  - precharge-upper-limit-microvolt:
> > 
> > When battery voltage has reached certain limit we change from
> > trickle-charge to next charging state (pre-charge for BD99954).
> > Allow
> > battery to specify this limit.
> > 
> >  - re-charge-voltage-microvolt:
> > 
> > Allow giving a battery specific voltage limit for chargers which
> > can
> > automatically re-start charging when battery has discharghed down
> > to
> > this limit.
> > 
> > - over-voltage-threshold-microvolt
> > 
> > Allow specifying voltage threshold after which the battery is
> > assumed to
> > be faulty.
> > 
> > Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
> > ---
> >  Documentation/devicetree/bindings/power/supply/battery.txt | 6
> > ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/power/supply/battery.txt
> > b/Documentation/devicetree/bindings/power/supply/battery.txt
> > index 5c913d4cf36c..7da044273e08 100644
> > --- a/Documentation/devicetree/bindings/power/supply/battery.txt
> > +++ b/Documentation/devicetree/bindings/power/supply/battery.txt
> > @@ -11,15 +11,21 @@ different type. This prevents unpredictable,
> > potentially harmful,
> >  behavior should a replacement that changes the battery type occur
> >  without a corresponding update to the dtb.
> >  
> > +Please note that not all charger drivers respect all of the
> > properties.
> > +
> >  Required Properties:
> >   - compatible: Must be "simple-battery"
> >  
> >  Optional Properties:
> > + - over-voltage-threshold-microvolt: battery over-voltage limit
> > + - re-charge-voltage-microvolt: limit to automatically start
> > charging again
> >   - voltage-min-design-microvolt: drained battery voltage
> >   - voltage-max-design-microvolt: fully charged battery voltage
> >   - energy-full-design-microwatt-hours: battery design energy
> >   - charge-full-design-microamp-hours: battery design capacity
> > + - tricklecharge-current-microamp: current for trickle-charge
> > phase
> 
> trickle-charge-...

Ok. I'll change this

> 
> >   - precharge-current-microamp: current for pre-charge phase
> > + - precharge-upper-limit-microvolt: limit when to change to
> > constant charging
> >   - charge-term-current-microamp: current for charge termination
> > phase
> >   - constant-charge-current-max-microamp: maximum constant input
> > current
> >   - constant-charge-voltage-max-microvolt: maximum constant input
> > voltage
> > -- 
> > 2.21.0
> > 
> > 
> > -- 
> > Matti Vaittinen, Linux device drivers
> > ROHM Semiconductors, Finland SWDC
> > Kiviharjunlenkki 1E
> > 90220 OULU
> > FINLAND
> > 
> > ~~~ "I don't think so," said Rene Descartes. Just then he vanished
> > ~~~
> > Simon says - in Latin please.
> > ~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
> > Thanks to Simon Glass for the translation =]