Re: [PATCH v3 12/12] iio: dac: ad5686: add gain control support

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The GAIN GPIO is unconditionally requested as driven low, causing a potential DAC output glitch during probe.
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commit 2f56ef5391a1b46c707191ed6f4562758e4e5acc
Author: Rodrigo Alencar <rodrigo.alencar@analog.com>

iio: dac: ad5686: add gain control support

This commit adds gain control support to the AD5686 DAC driver. It handles
gain multiplication either via an external hardware GAIN pin or through
internal control register bits, initializing the default scale based on
device properties.

> diff --git a/drivers/iio/dac/ad5686.c b/drivers/iio/dac/ad5686.c
> index 6ae788f665b4d..c186213a46f6d 100644
> --- a/drivers/iio/dac/ad5686.c
> +++ b/drivers/iio/dac/ad5686.c
[ ... ]
> @@ -579,6 +681,14 @@ int ad5686_probe(struct device *dev,
>  		return dev_err_probe(dev, PTR_ERR(st->ldac_gpio),
>  				     "Failed to get LDAC GPIO\n");
>  
> +	st->gain_gpio = devm_gpiod_get_optional(dev, "gain", GPIOD_OUT_LOW);
> +	if (IS_ERR(st->gain_gpio))
> +		return dev_err_probe(dev, PTR_ERR(st->gain_gpio),
> +				     "Failed to get GAIN GPIO\n");
> +
> +	st->double_scale = device_property_read_bool(dev, "adi,range-double");

[Severity: Medium]
Could this cause an unwanted glitch on the analog output during probe?

If the system is warm-booted and the DAC is already outputting voltage with
a 2x gain, unconditionally forcing the gain pin low here will abruptly halve
the output voltage before the device is reset or the pin is corrected later in
the probe sequence.

Would it be safer to read the adi,range-double property before requesting the
GPIO, so that the pin can be initialized to its correct target state without
the temporary drop to 1x gain?

> +	ad5686_init_scale_avail(st);
> +
>  	reset_control_assert(rstc);
>  	fsleep(1); /* reset pulse: comfortably bigger than the spec */
>  	reset_control_deassert(rstc);

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Sashiko AI review · https://sashiko.dev/#/patchset/20260616-ad5686-new-features-v3-0-f829fb7e9262@analog.com?part=12