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

[Matti Vaittinen <mazziesaccount@gmail.com>]

On 08/02/2025 18:52, Jonathan Cameron wrote:
> On Wed, 5 Feb 2025 15:38:16 +0200
> Matti Vaittinen <mazziesaccount@gmail.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@gmail.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!


Thanks :) I appreciate the time and energy invested here :)
> 
>> 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.

Oh, indeed. Thanks!

>> +
>> +		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?

Initially I did this.

But the code looked a bit dull because the evbitm, alarm-limit array and 
prints depend on the direction. Furthermore, the caller already knows 
the direction (as the caller does also handle directions separately), so 
doing:

foo(dir)
{
	if (dir == bar)
		...
	else
		...
}

...

if (dir == bar)
	foo(dir);
else
	foo(dir);

started to feel just a bit, meh. Hence I separated the stuff to own _lo 
and _hi functions.


>> +
>> +	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);
>> +}
> 

Yours,
   -- Matti