Re: [PATCH v2 06/12] iio: dac: ad5686: consume optional reset signal

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Premature reset line deassertion during power ramp-up due to the use of '_deasserted' combined with a manual pulse.
--

commit 61717352bc99739a9f89195c3320a934e033ad38
Author: Rodrigo Alencar <rodrigo.alencar@analog.com>

iio: dac: ad5686: consume optional reset signal

Add RESET pin GPIO support through an optional reset control, which is local
to the probe function, and include a delay for the required reset pulse width.

> diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
> index fc3863274b291..700798b80f044 100644
> --- a/drivers/iio/dac/ad5686.c
> +++ b/drivers/iio/dac/ad5686.c
[ ... ]
> @@ -506,7 +508,15 @@ int ad5686_probe(struct device *dev,
>  		return dev_err_probe(dev, -EINVAL,
>  				     "invalid or not provided vref voltage\n");
>  
> +	rstc = devm_reset_control_get_optional_exclusive_deasserted(dev, NULL);

[Severity: Medium]
Does this prematurely deassert the reset line during power ramp-up?

Because devm_reset_control_get_optional_exclusive_deasserted() automatically
and immediately deasserts the reset line upon acquisition, the reset line is
driven high while the power supply is still stabilizing, before the 5 us
power-up delay has elapsed.

This creates an unwanted rising edge on the reset pin during power ramp-up,
which could cause the device to enter an unknown state or latch up.

Should this use devm_reset_control_get_optional_exclusive() instead, which
does not modify the line state during acquisition, allowing the manual toggle
sequence below to safely reset the device after power is stable?

> +	if (IS_ERR(rstc))
> +		return dev_err_probe(dev, PTR_ERR(rstc),
> +				     "Failed to get reset control\n");
> +
>  	fsleep(5); /* power-up time */
> +	reset_control_assert(rstc);
> +	fsleep(1); /* reset pulse: comfortably bigger than the spec */
> +	reset_control_deassert(rstc);
>  
>  	/* Initialize masks to all ones */
>  	st->pwr_down_mask = ~0;

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260609-ad5686-new-features-v2-0-70b423f5c76d@analog.com?part=6