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

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Message-ID: <20180920165847.6xqzeoqzqkyotshx@earth.universe>
Date:   Thu, 20 Sep 2018 18:58:47 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Craig <ctatlor97@...il.com>, Baolin Wang <baolin.wang@...aro.org>,
        Rob Herring <robh+dt@...nel.org>
Cc:     linux-arm-msm@...r.kernel.org, Mark Rutland <mark.rutland@....com>,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 3/4] dt-bindings: power: supply: qcom_bms: Add bindings

[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>, ...;

-- Sebastian

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