linux-kernel - [PATCH 7/8] iio: adc: ad7476: Support ROHM BD79105

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Message-ID: <c7f94cdf9bdc6882953f6a074db3fd87570fa98b.1754463393.git.mazziesaccount@gmail.com>
Date: Wed, 6 Aug 2025 10:04:43 +0300
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 7/8] iio: adc: ad7476: Support ROHM BD79105

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.

Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
---
 drivers/iio/adc/ad7476.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7476.c b/drivers/iio/adc/ad7476.c
index 1f736be09663..fc98aadc4077 100644
--- a/drivers/iio/adc/ad7476.c
+++ b/drivers/iio/adc/ad7476.c
@@ -33,6 +33,7 @@ struct ad7476_chip_info {
 	struct iio_chan_spec		convst_channel[2];
 	void (*reset)(struct ad7476_state *);
 	void (*conversion_pre_op)(struct ad7476_state *st);
+	void (*conversion_post_op)(struct ad7476_state *st);
 	bool				has_vref;
 	bool				has_vdrive;
 };
@@ -64,6 +65,23 @@ static void ad7091_convst(struct ad7476_state *st)
 	udelay(1); /* Conversion time: 650 ns max */
 }
 
+static void bd79105_convst_disable(struct ad7476_state *st)
+{
+	if (!st->convst_gpio)
+		return;
+
+	gpiod_set_value(st->convst_gpio, 0);
+}
+
+static void bd79105_convst_enable(struct ad7476_state *st)
+{
+	if (!st->convst_gpio)
+		return;
+
+	gpiod_set_value(st->convst_gpio, 1);
+	udelay(1); /* 10ns required for conversion */
+}
+
 static irqreturn_t ad7476_trigger_handler(int irq, void  *p)
 {
 	struct iio_poll_func *pf = p;
@@ -81,6 +99,8 @@ static irqreturn_t ad7476_trigger_handler(int irq, void  *p)
 	iio_push_to_buffers_with_ts(indio_dev, st->data, sizeof(st->data),
 				    iio_get_time_ns(indio_dev));
 done:
+	if (st->chip_info->conversion_post_op)
+		st->chip_info->conversion_post_op(st);
 	iio_trigger_notify_done(indio_dev->trig);
 
 	return IRQ_HANDLED;
@@ -278,6 +298,20 @@ static const struct ad7476_chip_info ltc2314_14_chip_info = {
 	.has_vref = true,
 };
 
+static const struct ad7476_chip_info bd79105_chip_info = {
+	.convst_channel[0] = AD7091R_CONVST_CHAN(16),
+	.convst_channel[1] = IIO_CHAN_SOFT_TIMESTAMP(1),
+	/*
+	 * The BD79105 starts ADC data conversion when thw CONVSTART is set
+	 * HIGH. The CONVSTART must be kept HIGH until the data has been
+	 * read from the ADC.
+	 */
+	.conversion_pre_op = bd79105_convst_enable,
+	.conversion_post_op = bd79105_convst_disable,
+	.has_vref = true,
+	.has_vdrive = true,
+};
+
 static const struct iio_info ad7476_info = {
 	.read_raw = &ad7476_read_raw,
 };
@@ -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;
 
@@ -393,6 +426,7 @@ static const struct spi_device_id ad7476_id[] = {
 	{ "ads7866", (kernel_ulong_t)&ads7866_chip_info },
 	{ "ads7867", (kernel_ulong_t)&ads7867_chip_info },
 	{ "ads7868", (kernel_ulong_t)&ads7868_chip_info },
+	{ "bd79105", (kernel_ulong_t)&bd79105_chip_info },
 	/*
 	 * The ROHM BU79100G is identical to the TI's ADS7866 from the software
 	 * point of view. The binding document mandates the ADS7866 to be
-- 
2.50.1


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