From: Matti Vaittinen <mazziesaccount@gmail.com>

The term 'trickle-charging' is used to describe a very slow charging
phase, where electrons "trickle-in" the battery.

There are two different use-cases for this type of charging. At least
some Li-Ion batteries can benefit from very slow, constant current,
pre-pre phase 'trickle-charging', if a battery is very empty.

Some other batteries use top-off phase 'trickle-charging', which is
different from the above case.

The battery bindings use the term 'trickle-charge' without specifying
which of the use-cases properties are addressing. This has already
caused some confusion.

Clarify that the 'trickle-charge-current-microamp' refers to the first
one, the "pre-pre" -charging use-case.

Suggested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

---
Revision history:
  v2 => v3:
  - New patch
---
 .../devicetree/bindings/power/supply/battery.yaml          | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/power/supply/battery.yaml b/Documentation/devicetree/bindings/power/supply/battery.yaml
index 491488e7b970..bfb7b716ae13 100644
--- a/Documentation/devicetree/bindings/power/supply/battery.yaml
+++ b/Documentation/devicetree/bindings/power/supply/battery.yaml
@@ -64,7 +64,12 @@ properties:
     description: battery design capacity
 
   trickle-charge-current-microamp:
-    description: current for trickle-charge phase
+    description: current for trickle-charge phase.
+      Please note that the trickle-charging here, refers "wake-up" or
+      "pre-pre" -charging, for very empty batteries. Similar term is also
+      used for "maintenance" or "top-off" -charging of batteries (like
+      NiMh bq24400) - that is different and not controlled by this
+      property.
 
   precharge-current-microamp:
     description: current for pre-charge phase
-- 
2.51.0

On Wed, Nov 5, 2025 at 8:36 AM Matti Vaittinen
<matti.vaittinen@linux.dev> wrote:

> From: Matti Vaittinen <mazziesaccount@gmail.com>
>
> The term 'trickle-charging' is used to describe a very slow charging
> phase, where electrons "trickle-in" the battery.
>
> There are two different use-cases for this type of charging. At least
> some Li-Ion batteries can benefit from very slow, constant current,
> pre-pre phase 'trickle-charging', if a battery is very empty.
>
> Some other batteries use top-off phase 'trickle-charging', which is
> different from the above case.
>
> The battery bindings use the term 'trickle-charge' without specifying
> which of the use-cases properties are addressing. This has already
> caused some confusion.
>
> Clarify that the 'trickle-charge-current-microamp' refers to the first
> one, the "pre-pre" -charging use-case.
>
> Suggested-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

On Wed, Nov 05, 2025 at 09:36:16AM +0200, Matti Vaittinen wrote:
> From: Matti Vaittinen <mazziesaccount@gmail.com>
> 
> The term 'trickle-charging' is used to describe a very slow charging
> phase, where electrons "trickle-in" the battery.
> 
> There are two different use-cases for this type of charging. At least
> some Li-Ion batteries can benefit from very slow, constant current,
> pre-pre phase 'trickle-charging', if a battery is very empty.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Best regards,
Krzysztof