Re: [PATCH v2 02/15] dt-bindings: Add trickle-charge upper limit

[Krzysztof Kozlowski <krzk@kernel.org>]

On 29/10/2025 14:26, Linus Walleij wrote:
> On Wed, Oct 29, 2025 at 7:22 AM Matti Vaittinen
> <mazziesaccount@gmail.com> wrote:
> 
>>> But I believe this is wrong. Trickle charging does not switch to
>>> anything more, there is no fast charging after trickle. You have some
>>> sort of pre-pre-charging, which is just pre-charging.
>>
>> There is trickle, pre and fast-charge phases. Furthermore, the
>> fast-charge is further divided to CC and CV. Finally, if my memory
>> serves me well, Linus W did explain me that some chargers use
>> 'trickle-charging' as a _last_ charging phase for a full battery. Thus
>> the term 'trickle-charging' is slightly confusing - but it is already
>> used by the existing bindings...
>>
>> https://lore.kernel.org/all/20211116001755.2132036-1-linus.walleij@linaro.org/
> 
> I think we need to refer to a textbook or IEEE articles to get this
> terminology right.
> 
> As you say it appears "trickle-charging" is ambiguous.
> 
> Maybe what Krzysztof suggest to use: "pre-pre-charging" or
> "empty-battery-charging" or something like this is needed.
> 
> But we really need a trustworthy academic source here.

Trickle charging is accurate for both cases - pre-pre and top-off -
because it just describes very small current. That's why I found it in
many TI datasheets - mostly for Li-Ion batteries describing Matti's
case, but also in at least one case for Ni-Mh describing top-off (or
maintenance).

I am fine with the naming, but I want to be clear that this property
will describe trickle only in case of pre-pre charging. Termination
voltage simply does not fit the top-off/maintenance mode.

Best regards,
Krzysztof