linux-kernel - Re: [PATCH v10 6/8] iio: adc: Support ROHM BD79124 ADC

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Message-ID: <20250330173525.5d6e3d29@jic23-huawei>
Date: Sun, 30 Mar 2025 17:35:25 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Matti Vaittinen <mazziesaccount@...il.com>
Cc: Matti Vaittinen <matti.vaittinen@...rohmeurope.com>, Lars-Peter Clausen
 <lars@...afoo.de>, Nuno Sa <nuno.sa@...log.com>, David Lechner
 <dlechner@...libre.com>, Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Olivier Moysan <olivier.moysan@...s.st.com>, Guillaume Stols
 <gstols@...libre.com>, Dumitru Ceclan <mitrutzceclan@...il.com>, Trevor
 Gamblin <tgamblin@...libre.com>, Matteo Martelli
 <matteomartelli3@...il.com>, Alisa-Dariana Roman <alisadariana@...il.com>,
 Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, João
 Paulo Gonçalves <joao.goncalves@...adex.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH v10 6/8] iio: adc: Support ROHM BD79124 ADC

On Mon, 24 Mar 2025 09:13:42 +0200
Matti Vaittinen <mazziesaccount@...il.com> wrote:

> The ROHM BD79124 is a 12-bit, 8-channel, SAR ADC. The ADC supports
> an automatic measurement mode, with an alarm interrupt for out-of-window
> measurements. The window is configurable for each channel.
> 
> The I2C protocol for manual start of the measurement and data reading is
> somewhat peculiar. It requires the master to do clock stretching after
> sending the I2C slave-address until the slave has captured the data.
> Needless to say this is not well suopported by the I2C controllers.
> 
> Thus do not support the BD79124's manual measurement mode but implement
> the measurements using automatic measurement mode, relying on the
> BD79124's ability of storing latest measurements into register.
> 
> Support also configuring the threshold events for detecting the
> out-of-window events.
> 
> The BD79124 keeps asserting IRQ for as long as the measured voltage is
> out of the configured window. Thus, prevent the user-space from choking
> on the events and mask the received event for a fixed duration (1 second)
> when an event is handled.
> 
> The ADC input pins can be also configured as general purpose outputs.
> Make those pins which don't have corresponding ADC channel node in the
> device-tree controllable as GPO.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>

One trivial thing inline.

Jonathan

> diff --git a/drivers/iio/adc/rohm-bd79124.c b/drivers/iio/adc/rohm-bd79124.c
> new file mode 100644
> index 000000000000..099eccaa2232
> --- /dev/null
> +++ b/drivers/iio/adc/rohm-bd79124.c
> @@ -0,0 +1,1147 @@

>
> +static int bd79124_read_event_value(struct iio_dev *iio_dev,
> +				    const struct iio_chan_spec *chan,
> +				    enum iio_event_type type,
> +				    enum iio_event_direction dir,
> +				    enum iio_event_info info, int *val,
> +				    int *val2)
> +{
> +	struct bd79124_data *data = iio_priv(iio_dev);
> +	int ret, reg;
> +
> +	if (chan->channel >= BD79124_MAX_NUM_CHANNELS)
> +		return -EINVAL;
> +
> +	switch (info) {
> +	case IIO_EV_INFO_VALUE:
> +		if (dir == IIO_EV_DIR_RISING)
> +			*val = data->alarm_r_limit[chan->channel];
> +		else if (dir == IIO_EV_DIR_FALLING)
> +			*val = data->alarm_f_limit[chan->channel];
> +		else
> +			return -EINVAL;
> +
> +		return IIO_VAL_INT;
> +
> +	case IIO_EV_INFO_HYSTERESIS:
> +		reg = BD79124_GET_HYSTERESIS_REG(chan->channel);
> +		ret = regmap_read(data->map, reg, val);
> +		if (ret)
> +			return ret;
> +
> +		*val &= BD79124_MSK_HYSTERESIS;
> +		/*
> +		 * The data-sheet says the hysteresis register value needs to be
> +		 * sifted left by 3.

shifted