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 03:25:30 -0700
From:   Liam Breck <liam@...workimprov.net>
To:     Enric Balletbo Serra <eballetbo@...il.com>
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 Enric,



On Thu, Jun 1, 2017 at 1:18 AM, Enric Balletbo Serra
<eballetbo@...il.com> wrote:
> 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?

I'm curious to hear how your hw config requires constant-charge settings?

> 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.

You could certainly support constant-charge-* params in the charger
node. And it's easy to enable userspace to set these via sysfs.

> 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.

The charger could default constant-charge-* to the battery node's max values.

See also this discussion about similar issues.
https://patchwork.kernel.org/patch/9625331/


> 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
>>>>>