RE: [PATCH] dt-bindings: watchdog: renesas,wdt: Document RZ/G3L support

[Biju Das]

Hi Geert,

Thanks for the feedback.

> -----Original Message-----
> From: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> Sent: 05 May 2026 08:32
> Subject: Re: [PATCH] dt-bindings: watchdog: renesas,wdt: Document RZ/G3L support
> 
> Hi Biju,
> 
> On Fri, 6 Feb 2026 at 12:22, Biju <biju.das.au@xxxxxxxxx> wrote:
> > From: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> >
> > Document the support for the watchdog IP available on RZ/G3L SoC. The
> > watchdog IP available on RZ/G3L SoC is identical to the one found on
> > RZ/G2L SoC.
> >
> > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> 
> Thanks for your patch!
> 
> > ---
> > a/Documentation/devicetree/bindings/watchdog/renesas,rzg2l-wdt.yaml
> > +++ b/Documentation/devicetree/bindings/watchdog/renesas,rzg2l-wdt.yam
> > +++ l
> > @@ -18,6 +18,7 @@ properties:
> >                - renesas,r9a07g044-wdt    # RZ/G2{L,LC}
> >                - renesas,r9a07g054-wdt    # RZ/V2L
> >                - renesas,r9a08g045-wdt    # RZ/G3S
> > +              - renesas,r9a08g046-wdt    # RZ/G3L
> >            - const: renesas,rzg2l-wdt
> >
> >        - items:
> 
> However, there seems to be a small difference in the formulas for the timeout register value on the
> various SoCs:
> 
> RZ/G2L, RZ/G2UL, and RZ/V2L:
> 
>     WDTTIME setting value = \frac{WDT cycle}{(WDTn_CLK (n = 0,1,2) cycle × 1024 × 1024) − 1}
> 
> RZ/G3S and RZ/G3E:
> 
>     WDTTIME setting value = \frac{WDT cycle}{(WDTn_CLK (n = 0,1,2) cycle × 1024 × 1024} − 1
> 
> I.e. on the former, the "- 1" offset is inside the denominator, while on the former, it is outside the
> fraction.  I assume this is just a typo in the documentation, and both formulas are supposed to be
> identical, so

I agree it is a typo on RZ/G2L, RZ/G2UL, and RZ/V2L hardware manual, I will report this issue to
Documentation team.

as

Watchdog timer cycle = WDTn_CLK (n = 0, 1, 2) cycle × 1024 × 1024 × (WDTTIME setting value + 1)

To get min/max value 43.69/178956.97 msec with 24 MHz mentioned on all DoCs,

WDT min Cycle = 1024 * 1024 * (0 + 1) / (24 * 10^6) = 0.043690 = 43.69 msec
WDT max cycle = 1024 * 1024 * (0xfff + 1) / (24 * 10^6) = 178956.97 msec
	
Cheers,
Biju

> 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