linux-kernel - Re: [RFC PATCH v3 2/9] power: supply: add cap2ocv batinfo helper

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Date:   Thu, 18 Nov 2021 03:02:21 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc:     Matti Vaittinen <mazziesaccount@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>, rostokus@...il.com,
        fan.chen@...iatek.com, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-power@...rohmeurope.com
Subject: Re: [RFC PATCH v3 2/9] power: supply: add cap2ocv batinfo helper

On Tue, Nov 16, 2021 at 1:25 PM Matti Vaittinen
<matti.vaittinen@...rohmeurope.com> wrote:

> The power-supply core supports concept of OCV (Open Circuit Voltage) =>
> SOC (State Of Charge) conversion tables. Usually these tables are used
> to estimate SOC based on OCV. Some systems use so called "Zero Adjust"
> where at the near end-of-battery condition the SOC from coulomb counter
> is used to retrieve the OCV - and OCV and VSYS difference is used to
> re-estimate the battery capacity.
>
> Add helper to do look-up the other-way around and also get the OCV
> based on SOC
>
> Signed-off-by: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>

It seems you will need this for your chargers indeed.

> +int power_supply_dcap2ocv_simple(struct power_supply_battery_ocv_table *table,
> +                               int table_len, int dcap)
> +{
> +       int i, ocv, tmp;
> +
> +       for (i = 0; i < table_len; i++)
> +               if (dcap > table[i].capacity * 10)
> +                       break;
> +
> +       if (i > 0 && i < table_len) {
> +               tmp = (table[i - 1].ocv - table[i].ocv) *
> +                     (dcap - table[i].capacity * 10);
> +
> +               tmp /= (table[i - 1].capacity - table[i].capacity) * 10;
> +               ocv = tmp + table[i].ocv;
> +       } else if (i == 0) {
> +               ocv = table[0].ocv;
> +       } else {
> +               ocv = table[table_len - 1].ocv;
> +       }
> +
> +       return ocv;
> +}
> +EXPORT_SYMBOL_GPL(power_supply_dcap2ocv_simple);

Rewrite this using the library fixpoint interpolation function but just
copypasting from my patch:
https://lore.kernel.org/linux-pm/20211116230233.2167104-1-linus.walleij@linaro.org/

Other than that it looks good to me!

Yours,
Linus Walleij