linux-kernel - Re: [PATCH v1 07/15] iio: adc: ad7768-1: Add reset gpio

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Message-ID: <6b60de31-4bbb-4a94-a62b-63ccbacdf1b4@baylibre.com>
Date: Tue, 7 Jan 2025 17:40:53 -0600
From: David Lechner <dlechner@...libre.com>
To: Jonathan Santos <Jonathan.Santos@...log.com>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: Sergiu Cuciurean <sergiu.cuciurean@...log.com>, lars@...afoo.de,
 Michael.Hennerich@...log.com, jic23@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, marcelo.schmitt1@...il.com
Subject: Re: [PATCH v1 07/15] iio: adc: ad7768-1: Add reset gpio

On 1/7/25 9:25 AM, Jonathan Santos wrote:
> From: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> 
> Depending on the controller, the default state of a gpio can vary. This
> change excludes the probability that the dafult state of the ADC reset
> gpio will be HIGH if it will be passed as reference in the deivcetree.
> 
> Signed-off-by: Sergiu Cuciurean <sergiu.cuciurean@...log.com>
> ---
>  drivers/iio/adc/ad7768-1.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7768-1.c b/drivers/iio/adc/ad7768-1.c
> index 881446462ff5..f73b9aec8b0f 100644
> --- a/drivers/iio/adc/ad7768-1.c
> +++ b/drivers/iio/adc/ad7768-1.c
> @@ -161,6 +161,7 @@ struct ad7768_state {
>  	struct completion completion;
>  	struct iio_trigger *trig;
>  	struct gpio_desc *gpio_sync_in;
> +	struct gpio_desc *gpio_reset;
>  	const char *labels[ARRAY_SIZE(ad7768_channels)];
>  	/*
>  	 * DMA (thus cache coherency maintenance) may require the
> @@ -441,6 +442,18 @@ static int ad7768_setup(struct ad7768_state *st)
>  {
>  	int ret;
>  
> +	st->gpio_reset = devm_gpiod_get_optional(&st->spi->dev, "reset",
> +						 GPIOD_OUT_LOW);

Could be simplified by setting this to GPIOD_OUT_HIGH and drop

	gpiod_direction_output(st->gpio_reset, 1);

> +	if (IS_ERR(st->gpio_reset))
> +		return PTR_ERR(st->gpio_reset);
> +
> +	if (st->gpio_reset) {
> +		gpiod_direction_output(st->gpio_reset, 1);
> +		usleep_range(10, 15);
> +		gpiod_direction_output(st->gpio_reset, 0);
> +		usleep_range(10, 15);

prefer fsleep()

> +	}
> +

We can move the code below in an else since we don't need to do 2 resets.

>  	/*
>  	 * Two writes to the SPI_RESET[1:0] bits are required to initiate
>  	 * a software reset. The bits must first be set to 11, and then