Re: [PATCH 7/8] iio: adc: ad7476: Support ROHM BD79105

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Wed, Aug 06, 2025 at 10:04:43AM +0300, Matti Vaittinen wrote:
> The ROHM BD79105 is a simple 16-bit ADC accessible via SPI*.
> 
> The BD79105 has a CONVSTART pin, which must be set high to start the ADC
> conversion. Unlike with the ad7091 and ad7091r which also have a
> CONVSTART pin, the BD79105 requires that the pin must remain high also
> for the duration of the SPI access.
> 
> (*) Couple of words about the SPI. The BD79105 has pins named as
> CONVSTART, SCLK, DIN and DOUT. For the curious reader, DIN is not SPI
> ISO.
> 
> DIN is a signal which can be used as a chip-select. When DIN is pulled
> low, the ADC will output the completed measurement via DOUT as SCLK is
> clocked. According to the data-sheet, the DIN can also be used for
> daisy-chaining multiple ADCs. Also, DOUT can be used also for a
> 'data-ready' -IRQ. These modes aren't supported by this driver.
> 
> Support reading ADC scale and data from the BD79105 using SPI, when DIN
> is used as a chip-select.

...

> +static void bd79105_convst_disable(struct ad7476_state *st)
> +{
> +	if (!st->convst_gpio)
> +		return;

Dup code, please remove.

> +	gpiod_set_value(st->convst_gpio, 0);
> +}
> +
> +static void bd79105_convst_enable(struct ad7476_state *st)
> +{

> +	if (!st->convst_gpio)
> +		return;

With 10ns sleep in mind this is also unneeded check.

> +	gpiod_set_value(st->convst_gpio, 1);

> +	udelay(1); /* 10ns required for conversion */

We have ndelay(). But I believe toggling GPIO is much longer operation.

> +}

...

> @@ -347,7 +381,6 @@ static int ad7476_probe(struct spi_device *spi)
>  	if (st->convst_gpio)
>  		indio_dev->channels = st->chip_info->convst_channel;
>  	/* Setup default message */
> -
>  	st->xfer.rx_buf = &st->data;
>  	st->xfer.len = indio_dev->channels[0].scan_type.storagebits / 8;

Stray change.


-- 
With Best Regards,
Andy Shevchenko