Re: [PATCH 1/3] dt-bindings: rtc: Add Raspberry Pi 5 RTC binding

[Stefan Wahren <wahrenst@gmx.net>]

Am 10.09.26 um 09:08 schrieb Krzysztof Kozlowski:
> On 09/09/2026 22:24, Sander Speetjens wrote:
>> Thanks for your response
>>
>>> And more important, where is any interface to actually control the RTC?
>>> I see nothing, so your firmware is? Then this is not a separate device
>>> and you just added DTS for your driver, which is a no go (see writing
>>> bindings).
>> The RTC is a physical, battery-backed RTC, but the Raspberry Pi firmware
>> exposes its register interface exclusively through the firmware mailbox.
>> I initially used a firmware phandle so the RTC driver could obtain the
>> existing rpi_firmware instance.
FWIW Based on the official announcement [1], the Renesas DA9091 is a 
PMIC which has been customized for Raspberry Pi. So currently there is 
no datasheet available (yet).
But it's very likely that the GPU firmware of the BCM2712 communicate 
via I2C with this PMIC. Also this IC offers additional features like RTC 
and power button. So this driver only handles the RTC part.

Best regards

[1] - https://www.raspberrypi.com/news/introducing-raspberry-pi-5/
>>
>> Based on your comment, I think it is more appropriate to model
>> the RTC as a child device of rpi-firmware,
>> referencing to the existing firmware clock/reset/power services,
>> and have the driver obtain the firmware interface from its parent
>> rather than adding a phandle solely for driver plumbing.
>> Which also means moving this to arm/bcm/raspberrypi,bcm2835-firmware.yaml
>>
> Whether device has separate node, depends on it having dedicated
> resources. I don't see such here, so unlikely it should have a node in
> the first place (see writing bindings or DTS101 where exactly this
> question is asked).
>
> Best regards,
> Krzysztof