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

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Message-ID: <b30eed8e-c8f8-4077-9e6a-0217c5827981@kernel.org>
Date: Wed, 29 Oct 2025 07:17:20 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
 Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, Sebastian Reichel <sre@...nel.org>,
 Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd
 <sboyd@...nel.org>, Linus Walleij <linus.walleij@...aro.org>,
 Bartosz Golaszewski <brgl@...ev.pl>, Andreas Kemnade <andreas@...nade.info>,
 Alexandre Belloni <alexandre.belloni@...tlin.com>,
 linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
 linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
 linux-rtc@...r.kernel.org
Subject: Re: [PATCH v2 02/15] dt-bindings: Add trickle-charge upper limit

On 29/10/2025 07:03, Krzysztof Kozlowski wrote:
> On Mon, Oct 27, 2025 at 01:45:05PM +0200, Matti Vaittinen wrote:
>> Some of the chargers for lithium-ion batteries use a trickle-charging as
>> a first charging phase for very empty batteries, to "wake-up" the battery.
> 
> In the few cases I was dealing with charging circuits, trickle charging
> was used in context of top-off charging, so when battery is 100%. It's
> also documented at Wiki like that:
> https://en.wikipedia.org/wiki/Trickle_charging
> 
>> Trickle-charging is a low current, constant current phase. After the
>> voltage of the very empty battery has reached an upper limit for
>> trickle charging, the pre-charge phase is started with a higher current.
>>
>> Allow defining the upper limit for trickle charging voltage, after which
>> the charging should be changed to the pre-charging.
> 
> pre-charging is the trickle charging, no? Or you want to say that
> trickle-charging is pre-pre-charging? But then what is pre-charging in
> this binding?


Now I see that you added initial trickle-charging in commit
e3420b49949c79d6182dd8128fa7a3958da01b07. I looked at TI chargers for
LiIon/LiPo batteries and few popular models use the same meaning/cycles
as you here. Probably in LiIon/LiPo you cannot or should not use trickle
for top-off charging (CV phase).

For NiMh these TI chargers use term "Trickle Maintenance Charge" (e.g.
bq24400), so in separate or this patch please also clarify the
description of properties that this is trickle-charging for LiIon/LiPo
batteries, so the pre-pre charging.

Best regards,
Krzysztof