Re: [PATCH v3 2/2] watchdog: Add Watchdog Timer driver for RZ/V2H(P)

[Guenter Roeck]

On 8/6/24 06:47, Lad, Prabhakar wrote:
> Hi Guenter,
...
> > > +     /*
> > > +      * WDTCR
> > > +      * - CKS[7:4] - Clock Division Ratio Select - 0101b: oscclk/256
> > > +      * - RPSS[13:12] - Window Start Position Select - 11b: 100%
> > > +      * - RPES[9:8] - Window End Position Select - 11b: 0%
> > > +      * - TOPS[1:0] - Timeout Period Select - 11b: 16384 cycles (3FFFh)
> > > +      */
> > > +     rzv2h_wdt_setup(wdev, WDTCR_CKS_CLK_256 | WDTCR_RPSS_100 |
> > > +                     WDTCR_RPES_0 | WDTCR_TOPS_16384);
> > > +
> > > +     rzv2h_wdt_ping(wdev);
> > > +
> >
> > The need to ping the watchdog immediately after enabling it is unusual.
> > Please explain.
> The down counting operation starts only after the ping operation, so
> after starting the wdt a ping is issued here.

Please add that as comment to the code.

...

> Ive now updated restart with below, so that we dont touch clocks if
> they are already ON,
>
>      if (!watchdog_active(wdev)) {
>          ret = clk_enable(priv->pclk);
>          if (ret)
>              return ret;
>
>          ret = clk_enable(priv->oscclk);
>          if (ret) {
>              clk_disable(priv->pclk);
>              return ret;
>          }
>      }
>
>      if (!watchdog_active(wdev))
>          ret = reset_control_deassert(priv->rstc);
>      else
>          ret = reset_control_reset(priv->rstc);

Please rearrange to only require a single "if (!watchdog_active())".
Also, please add a comment explaining the need for calling
reset_control_reset() if the watchdog is active.

>      if (ret) {
>          clk_disable(priv->oscclk);
>          clk_disable(priv->pclk);
>          return ret;
>      }
>
>      /* delay to handle clock halt after de-assert operation */
>      udelay(3);
>
>
> > > +     /*
> > > +      * WDTCR
> > > +      * - CKS[7:4] - Clock Division Ratio Select - 0000b: oscclk/1
> > > +      * - RPSS[13:12] - Window Start Position Select - 00b: 25%
> > > +      * - RPES[9:8] - Window End Position Select - 00b: 75%
> > > +      * - TOPS[1:0] - Timeout Period Select - 00b: 1024 cycles (03FFh)
> > > +      */
> > > +     rzv2h_wdt_setup(wdev, WDTCR_CKS_CLK_1 | WDTCR_RPSS_25 |
> > > +                     WDTCR_RPES_75 | WDTCR_TOPS_1024);
> > > +     rzv2h_wdt_ping(wdev);
> > > +
> > Why is the ping here necessary ?
> The down counting starts after the refresh operation, hence the WDT is pinged.

Should be covered with the explanation in rzv2h_wdt_start().

Thanks,
Guenter