On Sat, Oct 19, 2024 at 10:47 AM Claudiu <claudiu.beznea@xxxxxxxxx> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
> The VBATTB IP of the Renesas RZ/G3S SoC controls the clock that is used
> by the RTC. The input to the VBATTB could be a 32KHz crystal
> or an external clock device.
>
> The HW block diagram for the clock generator is as follows:
>
> +----------+ XC `\
> RTXIN --->| |----->| \ +----+ VBATTCLK
> | 32K clock| | |----->|gate|----------->
> | osc | XBYP | | +----+
> RTXOUT --->| |----->| /
> +----------+ ,
>
> After discussions w/ Stephen Boyd the clock tree associated with this
> hardware block was exported in Linux as:
>
> vbattb-xtal
> xbyp
> xc
> mux
> vbattbclk
>
> where:
> - input-xtal is the input clock (connected to RTXIN, RTXOUT pins)
> - xc, xbyp are mux inputs
> - mux is the internal mux
> - vbattclk is the gate clock that feeds in the end the RTC
>
> to allow selecting the input of the MUX though assigned-clock DT
> properties, using the already existing clock drivers and avoid adding
> other DT properties. If the crystal is connected on RTXIN,
> RTXOUT pins the XC will be selected as mux input. If an external clock
> device is connected on RTXIN, RTXOUT pins the XBYP will be selected as
> mux input.
>
> The load capacitance of the internal crystal can be configured
> with renesas,vbattb-load-nanofarads DT property.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
> ---
>
> Changes in v4:
> - dropped oscillator from patch description
> - s/on-board/internal in patch description
> - updated dt-binding included file name in the driver as it has been
> renamed to include/dt-bindings/clock/renesas,r9a08g045-vbattb.h
> - dropped the "_BIT" from driver macros
> - used "quartz-load-femtofarads" dt property instead of adding a new one
> - register the "vbattclk" as critical clock as this feeds the RTC counter
> logic and it needs to stay on from the moment the RTC is configured;
> along with it, added a comment to express this.
Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
