Re: [PATCH v4 2/2] watchdog: dw_wdt: manage reset line during system suspend/resume

[Artem Shimko]

Hi Igor,

On Sat, Oct 24, 2026 at 9:46 PM Igor Velkov <iav@xxxxxx> wrote:
>
> On Sat, Oct 24, 2026 at 05:08:51PM +0300, Artem Shimko wrote:
> >       err = clk_prepare_enable(dw_wdt->pclk);
> > -     if (err) {
> > -             clk_disable_unprepare(dw_wdt->clk);
> > -             return err;
> > -     }
> > +     if (err)
> > +             goto unprepare_clk;
> > +
> > +     err = reset_control_deassert(dw_wdt->rst);
> > +     if (err)
> > +             goto unprepare_pclk;
>
> If clk_prepare_enable() fails in dw_wdt_resume(), we return with the reset
> still asserted. The _deasserted devres then asserts it once more at unbind,
> and on a shared control with deassert_count already at 0 that is a WARN_ON
> and -EINVAL; the next suspend hits the same. Deasserting before the clocks
> are enabled (or on the error paths) keeps every exit balanced.
> Not tested on hardware: I can't make the clock enable fail.

The official datasheet DW_apb_wdt_databook says:
The reset must be de-asserted synchronously after the rising edge of tclk.

That means we can't switch the sequence of clk and reset in suspend/resume.

At the same time, we can't do a deassert reset in the error paths by this
reason as well (when we have errors in clocks).

Given this, i think the WARN_ON on a clock failure is a minor concern
comparing to violating the hardware synchronization requirement. I'd
prefer to keep v4 as it is and not to send v5.

Best regards,
Artem