Re: [PATCH v3 1/9] regulator: core: Add "enable and wait" functions

[Chen-Yu Tsai]

On Tue, Jul 21, 2026 at 5:54 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Jul 21, 2026 at 03:52:15PM +0800, Chen-Yu Tsai wrote:
> > In device power sequencing and initialization use cases, it is common
> > for the driver to enable the regulator and then wait for a certain
> > period of time to pass before continuing.
> >
> > In cases where the regulator supply is always on, or has been turned on
> > or left on by another consumer, the driver could shorten the delay or
> > skip it altogether, provided that enough time has already passed since
> > the regulator was _actually_ turned on.
> >
> > Tracking this requires support from the regulator core. Introduce a
> > "last turned on" timestamp field to the regulator device, and "enable
> > and wait" functions to the single and bulk regulator consumer APIs.
> > The existing "enable without wait" functions are then converted to
> > macros that expand to the new functions.
> >
> > One case in particular is not optimized yet: a regulator left on either
> > by hardware reset default or by the bootloader, but does not have the
> > "regulator-boot-on" property set. As the enable timestamp only gets
> > updated when enabled by a consumer or by the core, the first enablement
> > always needs to wait.
>
> ...
>
> > -/* locks held by regulator_enable() */
> > -static int _regulator_enable(struct regulator *regulator)
> > +/* locks held by regulator_enable_and_wait() */
> > +static int _regulator_enable_and_wait(struct regulator *regulator, unsigned int wait_us)
>
> Hmm...
> This comment a bit confusing, perhaps adding some lockdep annotations help?
>
> ...

It's already there, just outside the diff context, the first line after
the variable declarations:

        lockdep_assert_held_once(&rdev->mutex.base);

> > +     if (wait_us) {
> > +             ktime_t end = ktime_add_us(rdev->last_on, wait_us);
> > +             s64 remaining = ktime_us_delta(end, ktime_get_boottime());
> > +
> > +             if (remaining > 0)
> > +                     fsleep(remaining);
>
> This style is discouraged as it makes maintenance harder. Better
>
>                 s64 remaining;
>
>                 remaining = ktime_us_delta(end, ktime_get_boottime());
>                 if (remaining > 0)
>                         fsleep(remaining);

Ack. FYI this will be rewritten based on concerns from Sashiko. The
wait will be pushed over to regulator_enable(), i.e. outside the scope
of the lock.

> > +     }
>
> ...
>
> >       /* private: Internal use */
> >       int ret;
> > +     unsigned int wait_us;
>
> If you want to make it more private (the above is only for kernel-doc) add
> __private annotation that will affect how sparse will check this.

Nice. Will add that.

> ...
>
> > -int __must_check regulator_enable(struct regulator *regulator);
> > +int __must_check regulator_enable_and_wait(struct regulator *regulator, unsigned int ms);
>
> ms or us? Please, double check all units.

Yeah this should be us.


Thanks
ChenYu