linux-kernel - Re: [PATCH v7 3/4] dt-bindings: power: supply: qcom

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Message-ID: <20180920221311.mrynysyh54si4g7f@earth.universe>
Date:   Fri, 21 Sep 2018 00:13:11 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Craig <ctatlor97@...il.com>, Rob Herring <robh+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 3/4] dt-bindings: power: supply: qcom_bms: Add bindings

Hi,

On Fri, Sep 21, 2018 at 04:08:28AM +0800, Baolin Wang wrote:
> Hi Sebastian,
> 
> On 21 September 2018 at 00:58, Sebastian Reichel
> <sebastian.reichel@...labora.com> wrote:
> > [Dropped a couple of people from CC, added Baolin]
> >
> > Hi Craig, Baolin and Rob,
> >
> > On Thu, Sep 20, 2018 at 03:32:29PM +0100, Craig wrote:
> >> On 16 September 2018 13:10:45 BST, Sebastian Reichel <sebastian.reichel@...labora.com> wrote:
> >> >Sorry for my long delay in reviewing this. I like the binding,
> >> >but the "qcom," specific properties should become common properties
> >> >in
> >> >
> >> >Documentation/devicetree/bindings/power/supply/battery.txt
> >> >and referenced via monitored-battery.
> >
> >> Thanks for the review, what bindings for ocv would you prefer? The
> >> spreadtrum ones or mine?
> >
> > Most importantly I want to see only one generic binding supporting
> > both use cases. As far as I can see there are two major differences:
> >
> > 1. Qcom uses legend properties and SC27XX embedds this into data
> > 2. Qcom supports temperature based mapping
> >
> > The second point is easy: Not having temperature information can
> > be a subset of the data with temperature info. The main thing to
> > discuss are the legend properties. I suppose we have these
> > proposals:
> >
> > Proposal A (from Qcom BMS binding):
> >
> > ocv-capacity-legend = /bits/ 8 <100 95 90 85 80 75 70 65 60 55 50 45 ...>;
> > ocv-temp-legend-celsius = /bits/ 8 <(-10) 0 25 50 65>;
> > ocv-lut-microvolt = <43050000 43050000 43030000 42990000
> >
> > Proposal B (from SC27XX binding):
> >
> > ocv-cap-table = <4185 100>, <4113 95>, <4066 90>, <4022 85> ...;
> >
> > I prefer the second binding (with mV -> uV), but I think it becomes
> > messy when temperature is added. What do you think about the
> > following proposal (derived from pinctrl style):
> >
> > Proposal C:
> >
> > ocv-capacity-table-temperatures = <(-10) 0 10>;
> > ocv-capacity-table-0 = <4185000 100>, <4113000 95>, <4066000 90>, ...;
> > ocv-capacity-table-1 = <4200000 100>, <4185000 95>, <4113000 90>, ...;
> > ocv-capacity-table-2 = <4250000 100>, <4200000 95>, <4185000 90>, ...;
> 
> For SC27XX, we have no temperatures consideration, but I think
> Proposal C can be compatible with our case.

Yes. I think for SC27XX proposal C could be used like this:

ocv-capacity-table-temperatures = <20>; /* room temperature */
ocv-capacity-table-0 = <4185000 100>, <4113000 95>, <4066000 90>, ...;

With only one curve defined it would be used for all temperatures.

-- Sebastian

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