[2/3] iio: potentiometer: Add support for the Renesas X9250 potentiometers

diff --git a/drivers/iio/potentiometer/Kconfig b/drivers/iio/potentiometer/Kconfig
index 01dd3f858d99..e6a9a3c67845 100644
--- a/drivers/iio/potentiometer/Kconfig
+++ b/drivers/iio/potentiometer/Kconfig
@@ -136,4 +136,14 @@  config TPL0102
 	  To compile this driver as a module, choose M here: the
 	  module will be called tpl0102.
 
+config X9250
+	tristate "Renesas X9250 quad controlled potentiometers"
+	depends on SPI
+	help
+	  Enable support for the Renesas X9250 quad controlled
+	  potentiometers.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called x9250.
+
 endmenu
diff --git a/drivers/iio/potentiometer/Makefile b/drivers/iio/potentiometer/Makefile
index 5ebb8e3bbd76..d11fb739176c 100644
--- a/drivers/iio/potentiometer/Makefile
+++ b/drivers/iio/potentiometer/Makefile
@@ -15,3 +15,4 @@  obj-$(CONFIG_MCP4131) += mcp4131.o
 obj-$(CONFIG_MCP4531) += mcp4531.o
 obj-$(CONFIG_MCP41010) += mcp41010.o
 obj-$(CONFIG_TPL0102) += tpl0102.o
+obj-$(CONFIG_X9250) += x9250.o
diff --git a/drivers/iio/potentiometer/x9250.c b/drivers/iio/potentiometer/x9250.c
new file mode 100644
index 000000000000..9d3831f36054
--- /dev/null
+++ b/drivers/iio/potentiometer/x9250.c
@@ -0,0 +1,233 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *
+ * x9250.c  --  Renesas X9250 potentiometers IIO driver
+ *
+ * Copyright 2023 CS GROUP France
+ *
+ * Author: Herve Codina <herve.codina@bootlin.com>
+ */
+
+#include <linux/iio/iio.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+
+struct x9250_cfg {
+	int kohms;
+};
+
+struct x9250 {
+	struct spi_device *spi;
+	const struct x9250_cfg *cfg;
+	struct mutex lock; /* Protect tx and rx buffers */
+	/* Cannot use stack area for SPI (dma-safe memory) */
+	u8 spi_tx_buf[3] __aligned(IIO_DMA_MINALIGN);
+	u8 spi_rx_buf[3] __aligned(IIO_DMA_MINALIGN);
+};
+
+#define X9250_CMD_RD_WCR(_p)    (0x90 | (_p))
+#define X9250_CMD_WR_WCR(_p)    (0xa0 | (_p))
+
+static int x9250_write8(struct x9250 *x9250, u8 cmd, u8 val)
+{
+	struct spi_transfer xfer = {
+		.tx_buf = &x9250->spi_tx_buf,
+		.len = 3,
+	};
+	int ret;
+
+	BUILD_BUG_ON(sizeof(x9250->spi_tx_buf) < 3);
+
+	mutex_lock(&x9250->lock);
+
+	x9250->spi_tx_buf[0] = 0x50;
+	x9250->spi_tx_buf[1] = cmd;
+	x9250->spi_tx_buf[2] = val;
+
+	ret = spi_sync_transfer(x9250->spi, &xfer, 1);
+
+	mutex_unlock(&x9250->lock);
+
+	return ret;
+}
+
+static int x9250_read8(struct x9250 *x9250, u8 cmd, u8 *val)
+{
+	struct spi_transfer xfer = {
+		.tx_buf = &x9250->spi_tx_buf,
+		.rx_buf = &x9250->spi_rx_buf,
+		.len = 3,
+	};
+	int ret;
+
+	BUILD_BUG_ON(sizeof(x9250->spi_tx_buf) < 3);
+	BUILD_BUG_ON(sizeof(x9250->spi_rx_buf) < 3);
+
+	mutex_lock(&x9250->lock);
+
+	x9250->spi_tx_buf[0] = 0x50;
+	x9250->spi_tx_buf[1] = cmd;
+
+	ret = spi_sync_transfer(x9250->spi, &xfer, 1);
+	if (ret)
+		goto end;
+
+	*val = x9250->spi_rx_buf[2];
+	ret = 0;
+end:
+	mutex_unlock(&x9250->lock);
+	return ret;
+}
+
+#define X9250_CHANNEL(ch) {						\
+	.type = IIO_RESISTANCE,						\
+	.indexed = 1,							\
+	.output = 1,							\
+	.channel = (ch),						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_RAW),	\
+}
+
+static const struct iio_chan_spec x9250_channels[] = {
+	X9250_CHANNEL(0),
+	X9250_CHANNEL(1),
+	X9250_CHANNEL(2),
+	X9250_CHANNEL(3),
+};
+
+static int x9250_read_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			  int *val, int *val2, long mask)
+{
+	struct x9250 *x9250 = iio_priv(indio_dev);
+	int ch = chan->channel;
+	int ret;
+	u8 v;
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		ret = x9250_read8(x9250, X9250_CMD_RD_WCR(ch), &v);
+		if (ret)
+			return ret;
+		*val = v;
+		return IIO_VAL_INT;
+
+	case IIO_CHAN_INFO_SCALE:
+		*val = 1000 * x9250->cfg->kohms;
+		*val2 = U8_MAX;
+		return IIO_VAL_FRACTIONAL;
+	}
+
+	return -EINVAL;
+}
+
+static int x9250_read_avail(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			    const int **vals, int *type, int *length, long mask)
+{
+	static const int range[] = {0, 1, 255}; /* min, step, max */
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*length = ARRAY_SIZE(range);
+		*vals = range;
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_RANGE;
+	}
+
+	return -EINVAL;
+}
+
+static int x9250_write_raw(struct iio_dev *indio_dev, struct iio_chan_spec const *chan,
+			   int val, int val2, long mask)
+{
+	struct x9250 *x9250 = iio_priv(indio_dev);
+	int ch = chan->channel;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	if (val > U8_MAX || val < 0)
+		return -EINVAL;
+
+	return x9250_write8(x9250, X9250_CMD_WR_WCR(ch), val);
+}
+
+static const struct iio_info x9250_info = {
+	.read_raw = x9250_read_raw,
+	.read_avail = x9250_read_avail,
+	.write_raw = x9250_write_raw,
+};
+
+enum x9250_type {
+	X9250T,
+	X9250U,
+};
+
+static const struct x9250_cfg x9250_cfg[] = {
+	[X9250T] = { .kohms =  100, },
+	[X9250U] = { .kohms =  50, },
+};
+
+static int x9250_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct x9250 *x9250;
+	int ret;
+
+	spi->bits_per_word = 8;
+	ret = spi_setup(spi);
+	if (ret < 0)
+		return ret;
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*x9250));
+	if (!indio_dev)
+		return -ENOMEM;
+
+	x9250 = iio_priv(indio_dev);
+	x9250->spi = spi;
+	x9250->cfg = device_get_match_data(&spi->dev);
+	if (!x9250->cfg)
+		x9250->cfg = &x9250_cfg[spi_get_device_id(spi)->driver_data];
+
+	mutex_init(&x9250->lock);
+
+	indio_dev->info = &x9250_info;
+	indio_dev->channels = x9250_channels;
+	indio_dev->num_channels = ARRAY_SIZE(x9250_channels);
+	indio_dev->name = spi_get_device_id(spi)->name;
+
+	spi_set_drvdata(spi, indio_dev);
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct of_device_id x9250_of_match[] = {
+	{ .compatible = "renesas,x9250t", &x9250_cfg[X9250T]},
+	{ .compatible = "renesas,x9250u", &x9250_cfg[X9250U]},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, x9250_of_match);
+
+static const struct spi_device_id x9250_id_table[] = {
+	{ "x9250t", X9250T },
+	{ "x9250u", X9250U },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, x9250_id_table);
+
+static struct spi_driver x9250_spi_driver = {
+	.driver  = {
+		.name   = "x9250",
+		.of_match_table = x9250_of_match,
+	},
+	.id_table = x9250_id_table,
+	.probe  = x9250_probe,
+};
+
+module_spi_driver(x9250_spi_driver);
+
+MODULE_AUTHOR("Herve Codina <herve.codina@bootlin.com>");
+MODULE_DESCRIPTION("X9250 ALSA SoC driver");
+MODULE_LICENSE("GPL");