On 12/02/2025 10:43:24+0000, Sudeep Holla wrote: > On Wed, Feb 12, 2025 at 02:35:32PM +0800, Peng Fan wrote: > > On Tue, Feb 11, 2025 at 04:59:53PM +0000, Sudeep Holla wrote: > > >On Tue, Jan 21, 2025 at 02:31:55PM +0000, Peng Fan wrote: > > >> > > >> It is the i.MX SCMI Protocol exports two RTCs using one protocol. > > >> > > >> Two RTC devices are created, but share one parent device. > > >> > > >> Do you mean each RTC device should have a unique parent device? > > >> > > > > > >Can you point where is this check for unique parent ? I am not so familiar > > >with RTC but I couldn't find myself with quick search. > > > > The RTC ops takes the rtc parent as input parameter > > https://elixir.bootlin.com/linux/v6.13.2/source/drivers/rtc/interface.c#L94 > > "err = rtc->ops->read_time(rtc->dev.parent, tm);" > > > > So in the rtc device driver, there is no way to know which rtc it is just > > from the parent device. > > > > If that is the expectation, you could create a platform or normal device > per instance of RTC on your platform and slap them as parent device. This would seem like the proper solution, why not using an MFD or auxiliary bus ? > > IIUC on any pure DT based system, a device node exists per RTC and hence > platform device associated with it. And the RTC devices are created with > parent pointing to unique platform device. > > > However i.MX SCMI BBM exports two RTCs(id: 0, id: 1), so to make it work for > > current RTC framework, we could only pick one RTC and pass the id to BBM > > server side. > > > > I am not sure whether Alexandre wanna me to update the code following each > > parent could only support one RTC or else. > > I want you to keep your changes local to your driver. I already stated back in 2018 that you were on your own with the imx-sc driver and that I don't like seeing multiple abstractions for existing RTCs. What is the actual use case behind needing to access both RTCs using Linux? Shouldn't this be handled on your firmware side? -- Alexandre Belloni, co-owner and COO, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
