Re: [PATCH v6 1/8] regulator: core: Add "enable and wait" functions

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] Mismatched timebase used for `last_off` initialization, which breaks `off_on_delay` semantics.
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commit 4cf0bd57fa8e1cfa65a0e290c2b4a44f43cb23db
Author: Chen-Yu Tsai <wenst@chromium.org>

regulator: core: Add "enable and wait" functions

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.

> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index 6a4008f387b5e..d7a193a3bcb28 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c

[ ... ]

> @@ -3061,6 +3108,8 @@ static int _regulator_do_enable(struct regulator_dev *rdev)
>  		fsleep(delay);
>  	}
>  
> +	rdev->last_on = ktime_get_boottime();
> +
>  	trace_regulator_enable_complete(rdev_get_name(rdev));
>  
>  	return 0;

[Severity: High]
This isn't a bug introduced by this patch, but since you are working with
timestamps in this function, could this timebase mismatch break off_on_delay
semantics?

In set_machine_constraints(), last_off is initialized with the monotonic clock:

	rdev->last_off = ktime_get();

But earlier in _regulator_do_enable(), the remaining delay is calculated using
the boottime clock:

	ktime_t end = ktime_add_us(rdev->last_off, rdev->desc->off_on_delay);
	s64 remaining = ktime_us_delta(end, ktime_get_boottime());

Because ktime_get_boottime() includes suspend time and ktime_get() does not,
the required delay is bypassed entirely if the system has accumulated suspend
time greater than the off_on_delay.

Will this lead to hardware sequence violations and incorrect functional behavior
unconditionally for any regulator with an off_on_delay registered after the
system has been suspended (such as via hotplug or module load)?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260901074930.764550-1-wenst@chromium.org?part=1