linux-kernel - Re: [PATCH v2 3/8] dt-bindings: rtc: isl12022: add bindings for battery alarm trip levels

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Message-ID: <0600a505-d1bf-f4be-57ef-51d34c77501e@linaro.org>
Date:   Tue, 13 Jun 2023 21:09:02 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        devicetree@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, linux-rtc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/8] dt-bindings: rtc: isl12022: add bindings for
 battery alarm trip levels

On 13/06/2023 15:00, Rasmus Villemoes wrote:
> The isl12022 has a built-in support for monitoring the voltage of the
> backup battery, and setting bits in the status register when that
> voltage drops below two predetermined levels (usually 85% and 75% of
> the nominal voltage). However, since it can operate at wide range of
> battery voltages (2.5V - 5.5V), one must configure those trip levels
> according to which battery is used on a given board.
> 
> Add bindings for defining these two trip levels. While the register
> and bit names suggest that they should correspond to 85% and 75% of
> the nominal battery voltage, the data sheet also says
> 
>   There are total of 7 levels that could be selected for the first
>   alarm. Any of the of levels could be selected as the first alarm
>   with no reference as to nominal Battery voltage level.
> 
> Hence this provides the hardware designer the ability to choose values
> based on the discharge characteristics of the battery chosen for the
> given product, rather than just having one battery-microvolt property
> and having the driver choose levels close to 0.85/0.75 times that.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
>  .../devicetree/bindings/rtc/intersil,isl12022.yaml | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/rtc/intersil,isl12022.yaml b/Documentation/devicetree/bindings/rtc/intersil,isl12022.yaml
> index 7c1e638d657a..d5d3a687a34d 100644
> --- a/Documentation/devicetree/bindings/rtc/intersil,isl12022.yaml
> +++ b/Documentation/devicetree/bindings/rtc/intersil,isl12022.yaml
> @@ -22,6 +22,18 @@ properties:
>    interrupts:
>      maxItems: 1
>  
> +  isil,trip-level85-microvolt:

Why encoding level85 in the property name? Your commit msg (datasheet)
suggests this is quite flexible, so why it cannot be just list of two
trip levels - for first and second interrupt?

> +    description: |

Do not need '|' unless you need to preserve formatting.

Best regards,
Krzysztof