linux-kernel - Re: [PATCH v3 1/4] dt-bindings: power: supply: add battery charge voltage/current

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Date:   Thu, 1 Jun 2017 10:18:54 +0200
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Liam Breck <liam@...workimprov.net>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Sebastian Reichel <sre@...nel.org>, linux-pm@...r.kernel.org,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Liam Breck <kernel@...workimprov.net>
Subject: Re: [PATCH v3 1/4] dt-bindings: power: supply: add battery charge voltage/current

Hi Liam,

2017-06-01 9:01 GMT+02:00 Liam Breck <liam@...workimprov.net>:
> Hi Enric,
>
> On Sat, May 27, 2017 at 1:11 PM, Enric Balletbo Serra
> <eballetbo@...il.com> wrote:
>> Hi Liam,
>>
>> 2017-05-26 23:20 GMT+02:00 Liam Breck <liam@...workimprov.net>:
>>> Hi Enric,
>>>
>>> On Fri, May 26, 2017 at 4:04 AM, Enric Balletbo i Serra
>>> <enric.balletbo@...labora.com> wrote:
>>>> Add charging voltage and current characteristics to the battery DT for
>>>> proper handling of the battery by fuel-gauge and charger chips.
>>>>
>>>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
>>>> ---
>>>> Changes since v2:
>>>>  - Requested by Sebastian Reichel
>>>>    - Move to its own patch and apply to simple-battery framework.
>>>> Changes since v1:
>>>>  - Requested by Rob Herring
>>>>    - Rename ti,charge-* to charge-* to be standard properties.
>>>>    - Use unit suffixes as per bindings/property-units.txt
>>>>
>>>>  Documentation/devicetree/bindings/power/supply/battery.txt | 4 ++++
>>>>  1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/power/supply/battery.txt b/Documentation/devicetree/bindings/power/supply/battery.txt
>>>> index 63a7028..c87a439 100644
>>>> --- a/Documentation/devicetree/bindings/power/supply/battery.txt
>>>> +++ b/Documentation/devicetree/bindings/power/supply/battery.txt
>>>> @@ -12,6 +12,8 @@ Optional Properties:
>>>>   - voltage-min-design-microvolt: drained battery voltage
>>>>   - energy-full-design-microwatt-hours: battery design energy
>>>>   - charge-full-design-microamp-hours: battery design capacity
>>>> + - charge-voltage-microvolt: battery charging voltage
>>>> + - charge-current-microamp: battery charging current
>>>
>>> I think you mean constant-charge-* which is how you surface these
>>> properties in your tps65217_charger patch.
>>>
>>
>> Yes, to be strict this is constant-charge-*
>
> The DT battery node should carry static battery characteristics. So on
> reflection, I think you want
>
> constant-charge-current-max-microamp
> constant-charge-voltage-max-microvolt
>
> The charger or the user could then safely apply any value <= those.
>
> Thoughts?
>

Hmm I see your point and I'm thinking now that actually this is not
what I wanted to do. What I wanted is set the charger voltage and the
current hence my first patchset was setting these properties in the
charger node not the battery.

Said that, I think that you have reason and what we want in battery
node is the current/voltage max values but we also need to implement a
mechanism to set the charging voltage/current from userspace or from
the DT for the charger. The charger should be able to set these values
and fail if, based in the battery specs, is not supported.

More thoughts?

>>> I'll add these to v14 of my patchset which adds simple-battery
>>> support. Rob requested a single patch for this file.
>>>
>>
>> Ok, I'll send the tps charger series without this patch, so please,
>> include this patch in your series.
>>
>>> I've been waiting for feedback on v13.2 from Sebastian. If I don't
>>> hear from him within a few days, I'll post v14.
>>>
>>>>  Batteries must be referenced by chargers and/or fuel-gauges
>>>>  using a phandle. The phandle's property should be named
>>>> @@ -24,6 +26,8 @@ Example:
>>>>                 voltage-min-design-microvolt = <3200000>;
>>>>                 energy-full-design-microwatt-hours = <5290000>;
>>>>                 charge-full-design-microamp-hours = <1430000>;
>>>> +               charge-voltage-microvolt = <4100000>;
>>>> +               charge-current-microamp = <300000>;
>>>>         };
>>>>
>>>>         charger: charger@11 {
>>>> --
>>>> 2.9.3
>>>>