[SRU][F/raspi][PATCH] rtc: class: support hctosys from modular RTC drivers

[Krzysztof Kozlowski]

On 04/05/2021 13:42, Dimitri John Ledkov wrote:
>>>
>>> If this is cherry picked, imho we must change config
>>> CONFIG_RTC_HCTOSYS or at least set it to something sane because
>>> currently on raspi it is set to CONFIG_RTC_HCTOSYS_DEVICE="rtc0" which
>>> always points at the non-battery backed RTC from the SOC.
>>
>> RPi does not have a RTC, so whoever adds it via overlay, probably
>> chooses one with a battery. Otherwise there is no much point of having
>> RTC...
> 
> That. I just don't know which RTC are available as rpi-hats and which
> dtb overlay they use and which rtc name they end up with.
> 
> If the properly working & battery backed RTC is added via overlay dtb
> and it ends up having rtc0 name, everything is fine. I just don't know
> if the overlays remove all other rtc nodes and like take over the rtc0
> name.

The first RTC registered will always have rtc0. Regardless of its
properties (e.g. with or without battery).

Best regards,
Krzysztof