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

[Krzysztof Kozlowski]

On 04/05/2021 13:22, Dimitri John Ledkov wrote:
> Hi,
> 
> This will introduce a regression in certain configurations as
> mentioned on https://github.com/systemd/systemd/issues/17737
> 
> I had a tentative patch to kernel to only advance time in rtc_hctosys
> only if it is newer than the one returned by ktime_get_real_ts64.

That's the mainline commit, so change for it (e.g. do not set the system
clock for modules) should go via upstream.

> However that went nowhere.
> 
> 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...

Best regards,
Krzysztof