Re: [PATCH v2 1/8] dt-bindings: rtc: let aux-voltage-chargeable supersede trickle-diode-disable

Rob Herring
2020-09-23T20:23:24Z

On Thu, 17 Sep 2020 20:32:39 +0200, Bastian Krause wrote:
> Some RTCs can be equipped with a chargeable battery or supercap.
> Every RTC allowing this whose driver's implement it are charged by
> default. To disable this the trickle-diode-disable flag exists.
>
> If a driver did not support charging and some time later one wants to
> add that feature, there is currently no way to do it without breaking
> dt backwards compatibility. RTCs on boards without the
> trickle-diode-disable flag in their device tree would suddenly charge
> their battery/supercap which is a change in behavior.
>
> Change that by introducing aux-voltage-chargeable, not as a flag but as
> a uint32 enum allowing to set "do not charge" (0) or "charge" (1). This
> dt property is optional, so we can now distinguish these cases.
>
> Care must be taken to support the old behavior for device trees without
> aux-voltage-chargeable nonetheless to stay compatible.
>
> Signed-off-by: Bastian Krause <bst@pengutronix.de>
> ---
> Changes since v1:
> - fixed dt_binding_check error by adding " |" after "description:"
>
> v1 notes:
> In a previous series aux-voltage-chargeable was added as a ds1307 dt
> property. Discussions lead to turning that into a generic rtc dt
> property:
> https://lore.kernel.org/linux-rtc/98fa7181-3ebe-d7c3-cfac-fee841c81e15@pengutronix.de/T/
> ---
> Documentation/devicetree/bindings/rtc/rtc.yaml | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>

Reviewed-by: Rob Herring <robh@kernel.org>