Re: [PATCH v12 3/3] gpio: gpio-ltc4283: Add support for the LTC4283 Swap Controller

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Hardware glitch due to setting GPIO direction to output before setting the output value.
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commit 50e4fcc0438eacaeeb8d0e7b85d04586253d71c0
Author: Nuno Sá <nuno.sa@analog.com>

gpio: gpio-ltc4283: Add support for the LTC4283 Swap Controller

This commit adds GPIO support for the LTC4283 device. It registers an auxiliary
driver and a gpio_chip for up to 8 pins that can be configured as GPIOs.

[ ... ]

> diff --git a/drivers/gpio/gpio-ltc4283.c b/drivers/gpio/gpio-ltc4283.c
> new file mode 100644
> index 0000000000000..6609443c5d62c
> --- /dev/null
> +++ b/drivers/gpio/gpio-ltc4283.c

[ ... ]

> +static int ltc4283_gpio_direction_output(struct gpio_chip *gc, unsigned int off, int val)
> +{
> +	struct ltc4283_gpio *st = gpiochip_get_data(gc);
> +	int ret;
> +
> +	ret = ltc4283_gpio_direction_set(st, off, false);
> +	if (ret)
> +		return ret;
> +
> +	return __ltc4283_gpio_set_value(st, off, val);

Does this sequence cause a hardware glitch on the GPIO line?

By calling ltc4283_gpio_direction_set() before __ltc4283_gpio_set_value(),
the pin is configured as an output while holding whatever residual logic
level was previously stored in the output value register.

If the residual value differs from the requested val, the hardware might
momentarily drive the pin with an unintended electrical state.

Should the driver write the intended output value first, and then configure
the pin as an output?

> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260430-ltc4283-support-v12-0-5dc9901f2567@analog.com?part=3