Hi Geert-san,
> From: Geert Uytterhoeven, Sent: Monday, June 3, 2019 6:59 PM
>
> Hi Shimoda-san,
>
> On Mon, Jun 3, 2019 at 11:31 AM Yoshihiro Shimoda
> <yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
> > According to the hardware manual of R-Car Gen2 and Gen3,
> > software should wait a few RLCK cycles as following:
> > - Delay 2 cycles before setting watchdog counter.
> > - Delay 3 cycles before disabling module clock.
> >
> > So, this patch adds such delays.
> >
> > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
>
> Thanks for your patch!
Thank you for your review!
> > --- a/drivers/watchdog/renesas_wdt.c
> > +++ b/drivers/watchdog/renesas_wdt.c
>
> > @@ -70,6 +71,16 @@ static int rwdt_init_timeout(struct watchdog_device *wdev)
> > return 0;
> > }
> >
> > +static void rwdt_wait(struct rwdt_priv *priv, unsigned long cycles)
>
> "unsigned int" should be sufficiently large.
I got it.
> > +{
> > + unsigned long periods, delays;
> > +
> > + periods = DIV_ROUND_UP(priv->clk_rate, cycles);
>
> Shouldn't the above be a division with rounding down (i.e. a plain C
> division), instead of a division with rounding up?
I have no idea which is the correct way (rounding down vs rounding up here).
At least, I tried to use rounding down before submitting patch and then
the result seemed the same. So, I submitted this patch with rounding up
(because the next step also used rounding up...).
> > + delays = DIV_ROUND_UP(1000000UL, periods);
>
> Given cycles is always a small number, accuracy can be improved, and one
> division can be avoided, by calculation this as:
>
> delays = DIV_ROUND_UP(cycles * 1000000 / priv->clk_rate);
Thank you for your suggest! I think so.
It should be "s/ \//,/" like below though :)
delays = DIV_ROUND_UP(cycles * 1000000, priv->clk_rate);
> > +
> > + usleep_range(delays, 2 * delays);
> > +}
>
> The rest looks good to me, so
> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
Thank you for your Reviewed-by tag! I'll submit v2 patch later.
Best regards,
Yoshihiro Shimoda
> 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
