iio: potentiometer: Add support for the Renesas X9250 potentiometers

The Renesas X9250 integrates four digitally controlled potentiometers.
On each potentiometer, the X9250T has a 100 kOhms total resistance and
the X9250U has a 50 kOhms total resistance.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20230509160852.158101-3-herve.codina@bootlin.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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

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

drivers/iio/potentiometer/x9250.c

+// 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/delay.h>
+#include <linux/gpio/consumer.h>
+#include <linux/iio/iio.h>
+#include <linux/limits.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+#include <linux/spi/spi.h>
+
+struct x9250_cfg {
+	const char *name;
+	int kohms;
+};
+
+struct x9250 {
+	struct spi_device *spi;
+	const struct x9250_cfg *cfg;
+	struct gpio_desc *wp_gpio;
+};
+
+#define X9250_ID		0x50
+#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)
+{
+	u8 txbuf[3];
+
+	txbuf[0] = X9250_ID;
+	txbuf[1] = cmd;
+	txbuf[2] = val;
+
+	return spi_write_then_read(x9250->spi, txbuf, ARRAY_SIZE(txbuf), NULL, 0);
+}
+
+static int x9250_read8(struct x9250 *x9250, u8 cmd, u8 *val)
+{
+	u8 txbuf[2];
+
+	txbuf[0] = X9250_ID;
+	txbuf[1] = cmd;
+
+	return spi_write_then_read(x9250->spi, txbuf, ARRAY_SIZE(txbuf), val, 1);
+}
+
+#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;
+	int ret;
+
+	if (mask != IIO_CHAN_INFO_RAW)
+		return -EINVAL;
+
+	if (val > U8_MAX || val < 0)
+		return -EINVAL;
+
+	gpiod_set_value_cansleep(x9250->wp_gpio, 0);
+	ret = x9250_write8(x9250, X9250_CMD_WR_WCR(ch), val);
+	gpiod_set_value_cansleep(x9250->wp_gpio, 1);
+
+	return ret;
+}
+
+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] = { .name = "x9250t", .kohms =  100, },
+	[X9250U] = { .name = "x9250u", .kohms =  50, },
+};
+
+static const char *const x9250_regulator_names[] = {
+	"vcc",
+	"avp",
+	"avn",
+};
+
+static int x9250_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct x9250 *x9250;
+	int ret;
+
+	ret = devm_regulator_bulk_get_enable(&spi->dev, ARRAY_SIZE(x9250_regulator_names),
+					     x9250_regulator_names);
+	if (ret)
+		return dev_err_probe(&spi->dev, ret, "Failed to get regulators\n");
+
+	/*
+	 * The x9250 needs a 5ms maximum delay after the power-supplies are set
+	 * before performing the first write (1ms for the first read).
+	 */
+	usleep_range(5000, 6000);
+
+	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 = spi_get_device_match_data(spi);
+	x9250->wp_gpio = devm_gpiod_get_optional(&spi->dev, "wp", GPIOD_OUT_LOW);
+	if (IS_ERR(x9250->wp_gpio))
+		return dev_err_probe(&spi->dev, PTR_ERR(x9250->wp_gpio),
+				     "failed to get wp gpio\n");
+
+	indio_dev->info = &x9250_info;
+	indio_dev->channels = x9250_channels;
+	indio_dev->num_channels = ARRAY_SIZE(x9250_channels);
+	indio_dev->name = x9250->cfg->name;
+
+	return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct of_device_id x9250_of_match[] = {
+	{ .compatible = "renesas,x9250t", .data = &x9250_cfg[X9250T]},
+	{ .compatible = "renesas,x9250u", .data = &x9250_cfg[X9250U]},
+	{ }
+};
+MODULE_DEVICE_TABLE(of, x9250_of_match);
+
+static const struct spi_device_id x9250_id_table[] = {
+	{ "x9250t", (kernel_ulong_t)&x9250_cfg[X9250T] },
+	{ "x9250u", (kernel_ulong_t)&x9250_cfg[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");