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

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Message-ID: <20251029-adamant-mamba-of-patience-cddb65@kuoka>
Date: Wed, 29 Oct 2025 07:03:02 +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 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?

> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> 
> ---
> Revision history:
>  RFCv1 =>:
>  - No changes
> ---
>  Documentation/devicetree/bindings/power/supply/battery.yaml | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/power/supply/battery.yaml b/Documentation/devicetree/bindings/power/supply/battery.yaml
> index 491488e7b970..66bed24b3dee 100644
> --- a/Documentation/devicetree/bindings/power/supply/battery.yaml
> +++ b/Documentation/devicetree/bindings/power/supply/battery.yaml
> @@ -66,6 +66,9 @@ properties:
>    trickle-charge-current-microamp:
>      description: current for trickle-charge phase
>  
> +  tricklecharge-upper-limit-microvolt:

Please keep existing format, look three lines above. trickle-charge-....

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.

Best regards,
Krzysztof