[PATCH v4 03/12] dt-bindings: clock: renesas,r9a08g045-vbattb: Document VBATTB

[Geert Uytterhoeven]

On Sat, Oct 19, 2024 at 10:47 AM Claudiu <claudiu.beznea at tuxon.dev> wrote:
> From: Claudiu Beznea <claudiu.beznea.uj at bp.renesas.com>
>
> The VBATTB IP of the Renesas RZ/G3S SoC controls the clock for RTC,
> the tamper detector and a small general usage memory of 128B.
>
> The VBATTB controller controls the clock for the RTC on the Renesas
> RZ/G3S. The HW block diagram for the clock logic is as follows:
>
>            +----------+ XC   `\
> RTXIN  --->|          |----->| \       +----+  VBATTCLK
>            | 32K clock|      |  |----->|gate|----------->
>            | osc      | XBYP |  |      +----+
> RTXOUT --->|          |----->| /
>            +----------+      ,/
>
> One could connect as input to this HW block either a crystal or
> an external clock device.
>
> After discussions w/ Stephen Boyd the clock tree associated with this
> hardware block was exported in Linux as:
>
> input-xtal
>   xbyp
>   xc
>      mux
>         vbattclk
>
> 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.
>
> This allows select the input of the mux based on the type of the
> connected input clock:
> - if the 32768 crystal is connected as input for the VBATTB,
>   the input of the mux should be xc
> - if an external clock device is connected as input for the VBATTB the
>   input of the mux should be xbyp
>
> Add bindings for the VBATTB controller.
>
> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj at bp.renesas.com>
> ---
>
> Changes in v4:
> - squashed with patch "Add clock IDs for the VBATTB controller" from v3
> - removed "oscillator" word from commit description
> - added assigned-clocks, assigned-clock-parents to the documentation example
> - used clock-controller for the node name
> - used "quartz-load-femtofarads" property for the load capacitance
> - renamed include/dt-bindings/clock/r9a08g045-vbattb.h to
>   include/dt-bindings/clock/renesas,r9a08g045-vbattb.h

Thanks for the update!

Reviewed-by: Geert Uytterhoeven <geert+renesas at glider.be>

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

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when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds