--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 Anshul Dalal <anshulusr@gmail.com>
+ *
+ * Driver for Microchip MCP4801, MCP4802, MCP4811, MCP4812, MCP4821 and MCP4822
+ *
+ * Based on the work of:
+ * Michael Welling (MCP4922 Driver)
+ *
+ * Datasheet:
+ * MCP48x1: https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
+ * MCP48x2: https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf
+ *
+ * TODO:
+ * - Configurable gain
+ * - Regulator control
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/spi/spi.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+
+#include <asm/unaligned.h>
+
+#define MCP4821_ACTIVE_MODE BIT(12)
+#define MCP4802_SECOND_CHAN BIT(15)
+
+/* DAC uses an internal Voltage reference of 4.096V at a gain of 2x */
+#define MCP4821_2X_GAIN_VREF_MV 4096
+
+enum mcp4821_supported_drvice_ids {
+ ID_MCP4801,
+ ID_MCP4802,
+ ID_MCP4811,
+ ID_MCP4812,
+ ID_MCP4821,
+ ID_MCP4822,
+};
+
+struct mcp4821_state {
+ struct spi_device *spi;
+ u16 dac_value[2];
+};
+
+struct mcp4821_chip_info {
+ const char *name;
+ int num_channels;
+ const struct iio_chan_spec channels[2];
+};
+
+#define MCP4821_CHAN(channel_id, resolution) \
+ { \
+ .type = IIO_VOLTAGE, .output = 1, .indexed = 1, \
+ .channel = (channel_id), \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW), \
+ .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE), \
+ .scan_type = { \
+ .realbits = (resolution), \
+ .shift = 12 - (resolution), \
+ }, \
+ }
+
+static const struct mcp4821_chip_info mcp4821_chip_info_table[6] = {
+ [ID_MCP4801] = {
+ .name = "mcp4801",
+ .num_channels = 1,
+ .channels = {
+ MCP4821_CHAN(0, 8),
+ },
+ },
+ [ID_MCP4802] = {
+ .name = "mcp4802",
+ .num_channels = 2,
+ .channels = {
+ MCP4821_CHAN(0, 8),
+ MCP4821_CHAN(1, 8),
+ },
+ },
+ [ID_MCP4811] = {
+ .name = "mcp4811",
+ .num_channels = 1,
+ .channels = {
+ MCP4821_CHAN(0, 10),
+ },
+ },
+ [ID_MCP4812] = {
+ .name = "mcp4812",
+ .num_channels = 2,
+ .channels = {
+ MCP4821_CHAN(0, 10),
+ MCP4821_CHAN(1, 10),
+ },
+ },
+ [ID_MCP4821] = {
+ .name = "mcp4821",
+ .num_channels = 1,
+ .channels = {
+ MCP4821_CHAN(0, 12),
+ },
+ },
+ [ID_MCP4822] = {
+ .name = "mcp4822",
+ .num_channels = 2,
+ .channels = {
+ MCP4821_CHAN(0, 12),
+ MCP4821_CHAN(1, 12),
+ },
+ },
+};
+
+static int mcp4821_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int *val,
+ int *val2, long mask)
+{
+ struct mcp4821_state *state;
+
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ state = iio_priv(indio_dev);
+ *val = state->dac_value[chan->channel];
+ return IIO_VAL_INT;
+ case IIO_CHAN_INFO_SCALE:
+ *val = MCP4821_2X_GAIN_VREF_MV;
+ *val2 = chan->scan_type.realbits;
+ return IIO_VAL_FRACTIONAL_LOG2;
+ default:
+ return -EINVAL;
+ }
+}
+
+static int mcp4821_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *chan, int val,
+ int val2, long mask)
+{
+ struct mcp4821_state *state = iio_priv(indio_dev);
+ u16 write_val;
+ __be16 write_buffer;
+ int ret;
+
+ if (val2 != 0)
+ return -EINVAL;
+
+ if (val < 0 || val >= BIT(chan->scan_type.realbits))
+ return -EINVAL;
+
+ if (mask != IIO_CHAN_INFO_RAW)
+ return -EINVAL;
+
+ write_val = MCP4821_ACTIVE_MODE | val << chan->scan_type.shift;
+ if (chan->channel)
+ write_val |= MCP4802_SECOND_CHAN;
+
+ write_buffer = cpu_to_be16(write_val);
+ ret = spi_write(state->spi, &write_buffer, sizeof(write_buffer));
+ if (ret) {
+ dev_err(&state->spi->dev, "Failed to write to device: %d", ret);
+ return ret;
+ }
+
+ state->dac_value[chan->channel] = val;
+
+ return 0;
+}
+
+static const struct iio_info mcp4821_info = {
+ .read_raw = &mcp4821_read_raw,
+ .write_raw = &mcp4821_write_raw,
+};
+
+static int mcp4821_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct mcp4821_state *state;
+ const struct mcp4821_chip_info *info;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
+ if (indio_dev == NULL)
+ return -ENOMEM;
+
+ state = iio_priv(indio_dev);
+ state->spi = spi;
+
+ info = spi_get_device_match_data(spi);
+ indio_dev->name = info->name;
+ indio_dev->info = &mcp4821_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = info->channels;
+ indio_dev->num_channels = info->num_channels;
+
+ return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+#define MCP4821_COMPATIBLE(of_compatible, id) \
+ { \
+ .compatible = of_compatible, \
+ .data = &mcp4821_chip_info_table[id] \
+ }
+
+static const struct of_device_id mcp4821_of_table[] = {
+ MCP4821_COMPATIBLE("microchip,mcp4801", ID_MCP4801),
+ MCP4821_COMPATIBLE("microchip,mcp4802", ID_MCP4802),
+ MCP4821_COMPATIBLE("microchip,mcp4811", ID_MCP4811),
+ MCP4821_COMPATIBLE("microchip,mcp4812", ID_MCP4812),
+ MCP4821_COMPATIBLE("microchip,mcp4821", ID_MCP4821),
+ MCP4821_COMPATIBLE("microchip,mcp4822", ID_MCP4822),
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mcp4821_of_table);
+
+static const struct spi_device_id mcp4821_id_table[] = {
+ { "mcp4801", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4801]},
+ { "mcp4802", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4802]},
+ { "mcp4811", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4811]},
+ { "mcp4812", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4812]},
+ { "mcp4821", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4821]},
+ { "mcp4822", (kernel_ulong_t)&mcp4821_chip_info_table[ID_MCP4822]},
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, mcp4821_id_table);
+
+static struct spi_driver mcp4821_driver = {
+ .driver = {
+ .name = "mcp4821",
+ .of_match_table = mcp4821_of_table,
+ },
+ .probe = mcp4821_probe,
+ .id_table = mcp4821_id_table,
+};
+module_spi_driver(mcp4821_driver);
+
+MODULE_AUTHOR("Anshul Dalal <anshulusr@gmail.com>");
+MODULE_DESCRIPTION("Microchip MCP4821 DAC Driver");
+MODULE_LICENSE("GPL");
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