linux-kernel - Re: [PATCH v2 3/5] iio: adc: Support ROHM BD79124 ADC

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Message-ID: <20250208165208.3560237f@jic23-huawei>
Date: Sat, 8 Feb 2025 16:52:08 +0000
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>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Nuno Sa
 <nuno.sa@...log.com>, David Lechner <dlechner@...libre.com>,
 linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/5] iio: adc: Support ROHM BD79124 ADC

On Wed, 5 Feb 2025 15:38:16 +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 the driver does not support the BD79124's manual measurement mode
> but implements the measurements using automatic measurement mode relying
> on the BD79124's ability of storing latest measurements into register.
> 
> The driver does also support 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 the driver masks the received event
> for a fixed duration (1 second) when an event is handled. This prevents
> the user-space from choking on the events
> 
> The ADC input pins can be also configured as general purpose outputs.
> Those pins which don't have corresponding ADC channel node in the
> device-tree will be controllable as GPO.
> 
> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>

Hi Matti,

Just a few really trivial comments though this wasn't my most thorough
of reviews as ran out of time / energy today!

Jonathan

> diff --git a/drivers/iio/adc/rohm-bd79124.c b/drivers/iio/adc/rohm-bd79124.c
> new file mode 100644
> index 000000000000..ea93762a24cc
> --- /dev/null
> +++ b/drivers/iio/adc/rohm-bd79124.c
> @@ -0,0 +1,1149 @@


> +static int bd79124_write_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 reg;
> +
> +	if (chan->channel >= BD79124_MAX_NUM_CHANNELS)
> +		return -EINVAL;
> +
> +	switch (info) {
> +	case IIO_EV_INFO_VALUE:
> +		if (dir == IIO_EV_DIR_RISING) {
> +			guard(mutex)(&data->mutex);
> +
> +			data->alarm_r_limit[chan->channel] = val;
> +			reg = BD79124_GET_HIGH_LIMIT_REG(chan->channel);
> +		} else if (dir == IIO_EV_DIR_FALLING) {
> +			guard(mutex)(&data->mutex);
> +
> +			data->alarm_f_limit[chan->channel] = val;
> +			reg = BD79124_GET_LOW_LIMIT_REG(chan->channel);
> +		} else {
> +			return -EINVAL;
> +		}
> +		/*
> +		 * We don't want to enable the alarm if it is not enabled or
> +		 * if it is suppressed. In that case skip writing to the
> +		 * register.
> +		 */
> +		if (!(data->alarm_monitored[chan->channel] & BIT(dir)) ||
> +		    data->alarm_suppressed[chan->channel] & BIT(dir))
> +			return 0;
> +
> +		return bd79124_write_int_to_reg(data, reg, val);
> +
> +	case IIO_EV_INFO_HYSTERESIS:
> +			reg = BD79124_GET_HYSTERESIS_REG(chan->channel);
> +			val >>= 3;
Odd indent.
> +
> +		return regmap_update_bits(data->map, reg, BD79124_MASK_HYSTERESIS,
> +					  val);
> +	default:
> +		return -EINVAL;
> +	}
> +}


> +static void bd79124_re_enable_lo(struct bd79124_data *data, unsigned int channel)
> +{
> +	int ret, evbit = BIT(IIO_EV_DIR_FALLING);
> +
> +	if (!(data->alarm_suppressed[channel] & evbit))
> +		return;
> +
> +	data->alarm_suppressed[channel] &= (~evbit);
> +
> +	if (!(data->alarm_monitored[channel] & evbit))
> +		return;
> +
> +	ret = bd79124_write_int_to_reg(data, BD79124_GET_LOW_LIMIT_REG(channel),
> +				       data->alarm_f_limit[channel]);
> +	if (ret)
> +		dev_warn(data->dev, "Low limit enabling failed for channel%d\n",
> +			 channel);
> +}
> +
> +static void bd79124_re_enable_hi(struct bd79124_data *data, unsigned int channel)
> +{
> +	int ret, evbit = BIT(IIO_EV_DIR_RISING);
> +
> +	if (!(data->alarm_suppressed[channel] & evbit))
> +		return;
> +
> +	data->alarm_suppressed[channel] &= (~evbit);
> +
> +	if (!(data->alarm_monitored[channel] & evbit))
> +		return;
This lot is very similar to the lo variant. Can we combine them or
use some helper for both?
> +
> +	ret = bd79124_write_int_to_reg(data, BD79124_GET_HIGH_LIMIT_REG(channel),
> +				       data->alarm_r_limit[channel]);
> +	if (ret)
> +		dev_warn(data->dev, "High limit enabling failed for channel%d\n",
> +			 channel);
> +}