linux-kernel - Re: [PATCH v6 06/10] iio: adc: Support ROHM BD79124 ADC

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Message-ID: <20250310202640.71f7ec1f@jic23-huawei>
Date: Mon, 10 Mar 2025 20:26:40 +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>, 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 v6 06/10] iio: adc: Support ROHM BD79124 ADC

On Mon, 10 Mar 2025 14:56:47 +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>


The comment below wins the Monday award for the trivial :)


> diff --git a/drivers/iio/adc/rohm-bd79124.c b/drivers/iio/adc/rohm-bd79124.c
> new file mode 100644
> index 000000000000..f63141daf5e2
> --- /dev/null
> +++ b/drivers/iio/adc/rohm-bd79124.c

> +static int bd79124_enable_event(struct bd79124_data *data,
> +		enum iio_event_direction dir, unsigned int channel)
> +{
> +	int dir_bit = BIT(dir);
> +	int reg, ret;
> +	u16 *limit;
> +
> +	guard(mutex)(&data->mutex);
> +	/* Set channel to be measured */
> +	ret = bd79124_start_measurement(data, channel);
> +	if (ret)
> +		return ret;
> +
> +	data->alarm_monitored[channel] |= dir_bit;
> +
> +	/* Add the channel to the list of monitored channels */
> +	ret = regmap_set_bits(data->map, BD79124_REG_ALERT_CH_SEL,
> +			      BIT(channel));
> +	if (ret)
> +		return ret;
> +
> +	if (dir == IIO_EV_DIR_RISING) {
> +		limit = &data->alarm_f_limit[channel];
> +		reg = BD79124_GET_HIGH_LIMIT_REG(channel);
> +	} else {
> +		limit = &data->alarm_f_limit[channel];
> +		reg = BD79124_GET_LOW_LIMIT_REG(channel);
> +	}
> +	/*
> +	 * Don't write the new limit to the hardware if we are in the
> +	 * rate-limit period. The timer which re-enables the event will set
> +	 * the limit.
> +	 */
> +	if (!(data->alarm_suppressed[channel] & dir_bit)) {
> +		ret = bd79124_write_int_to_reg(data, reg, *limit);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/*
> +	 * Enable comparator. Trust the regmap cache, no need to check
> +	 * if it was already enabled.
> +	 *
> +	 * We could do this in the hw-init, but there may be users who
> +	 * never enable alarms and for them it makes sense to not
> +	 * enable the comparator at probe.
> +	 */
> +	return regmap_set_bits(data->map, BD79124_REG_GEN_CFG,
> +				      BD79124_MASK_DWC_EN);
> +
Stray blank line.

> +}
>