1 files changed, 131 insertions, 0 deletions
diff --git a/drivers/iio/resolver/ad2s90.c b/drivers/iio/resolver/ad2s90.c
new file mode 100644
index 000000000000..a41f5cb10da5
--- /dev/null
+++ b/drivers/iio/resolver/ad2s90.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ad2s90.c simple support for the ADI Resolver to Digital Converters: AD2S90
+ *
+ * Copyright (c) 2010-2010 Analog Devices Inc.
+ */
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/device.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+/*
+ * Although chip's max frequency is 2Mhz, it needs 600ns between CS and the
+ * first falling edge of SCLK, so frequency should be at most 1 / (2 * 6e-7)
+ */
+#define AD2S90_MAX_SPI_FREQ_HZ  830000
+
+struct ad2s90_state {
+	struct mutex lock; /* lock to protect rx buffer */
+	struct spi_device *sdev;
+	u8 rx[2] ____cacheline_aligned;
+};
+
+static int ad2s90_read_raw(struct iio_dev *indio_dev,
+			   struct iio_chan_spec const *chan,
+			   int *val,
+			   int *val2,
+			   long m)
+{
+	int ret;
+	struct ad2s90_state *st = iio_priv(indio_dev);
+
+	if (chan->type != IIO_ANGL)
+		return -EINVAL;
+
+	switch (m) {
+	case IIO_CHAN_INFO_SCALE:
+		/* 2 * Pi / 2^12 */
+		*val = 6283; /* mV */
+		*val2 = 12;
+		return IIO_VAL_FRACTIONAL_LOG2;
+	case IIO_CHAN_INFO_RAW:
+		mutex_lock(&st->lock);
+		ret = spi_read(st->sdev, st->rx, 2);
+		if (ret < 0) {
+			mutex_unlock(&st->lock);
+			return ret;
+		}
+		*val = (((u16)(st->rx[0])) << 4) | ((st->rx[1] & 0xF0) >> 4);
+
+		mutex_unlock(&st->lock);
+
+		return IIO_VAL_INT;
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static const struct iio_info ad2s90_info = {
+	.read_raw = ad2s90_read_raw,
+};
+
+static const struct iio_chan_spec ad2s90_chan = {
+	.type = IIO_ANGL,
+	.indexed = 1,
+	.channel = 0,
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+};
+
+static int ad2s90_probe(struct spi_device *spi)
+{
+	struct iio_dev *indio_dev;
+	struct ad2s90_state *st;
+
+	if (spi->max_speed_hz > AD2S90_MAX_SPI_FREQ_HZ) {
+		dev_err(&spi->dev, "SPI CLK, %d Hz exceeds %d Hz\n",
+			spi->max_speed_hz, AD2S90_MAX_SPI_FREQ_HZ);
+		return -EINVAL;
+	}
+
+	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
+	if (!indio_dev)
+		return -ENOMEM;
+	st = iio_priv(indio_dev);
+	spi_set_drvdata(spi, indio_dev);
+
+	mutex_init(&st->lock);
+	st->sdev = spi;
+	indio_dev->dev.parent = &spi->dev;
+	indio_dev->info = &ad2s90_info;
+	indio_dev->modes = INDIO_DIRECT_MODE;
+	indio_dev->channels = &ad2s90_chan;
+	indio_dev->num_channels = 1;
+	indio_dev->name = spi_get_device_id(spi)->name;
+
+	return devm_iio_device_register(indio_dev->dev.parent, indio_dev);
+}
+
+static const struct of_device_id ad2s90_of_match[] = {
+	{ .compatible = "adi,ad2s90", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, ad2s90_of_match);
+
+static const struct spi_device_id ad2s90_id[] = {
+	{ "ad2s90" },
+	{}
+};
+MODULE_DEVICE_TABLE(spi, ad2s90_id);
+
+static struct spi_driver ad2s90_driver = {
+	.driver = {
+		.name = "ad2s90",
+		.of_match_table = ad2s90_of_match,
+	},
+	.probe = ad2s90_probe,
+	.id_table = ad2s90_id,
+};
+module_spi_driver(ad2s90_driver);
+
+MODULE_AUTHOR("Graff Yang <graff.yang@gmail.com>");
+MODULE_DESCRIPTION("Analog Devices AD2S90 Resolver to Digital SPI driver");
+MODULE_LICENSE("GPL v2");