[PATCH 2/2] iio: dac: driver for MCP4821

From: Anshul Dalal
Date: Fri Nov 17 2023 - 02:33:40 EST

Adds driver for the MCP48xx series of DACs.

Device uses a simplex SPI channel.
To set the value of an output channel, a 16-bit
data of following format must be written:

Bit field | Description
15 [MSB] | Channel selection bit
0 -> Channel A
1 -> Channel B
13 | Output Gain Selection bit
0 -> 2x Gain (Vref = 4.096V)
1 -> 1x Gain (Vref = 2.048V)
12 | Output Shutdown Control bit
0 -> Shutdown the selected channel
1 -> Active mode operation
11-0 [LSB]| DAC Input Data bits
Value's big endian representation is
taken as input for the selected DAC
channel.
For devices with a resolution of less
than 12-bits, only the x most
significant bits are considered where
x is the resolution of the device.
Reference: Page#22 [MCP48x2 Datasheet]

Supported devices:
+---------+--------------+-------------+
| Device | Resolution | Channels |
|---------|--------------|-------------|
| MCP4801 | 8-bit | 1 |
| MCP4811 | 10-bit | 1 |
| MCP4821 | 12-bit | 1 |
| MCP4802 | 8-bit | 2 |
| MCP4812 | 10-bit | 2 |
| MCP4822 | 12-bit | 2 |
+---------+--------------+-------------+

Devices tested:
MCP4821 [12-bit single channel]
MCP4802 [8-bit dual channel]

Tested on Raspberry Pi Zero 2W

Datasheet:
[MCP48x1] https://ww1.microchip.com/downloads/en/DeviceDoc/22244B.pdf
[MCP48x2] https://ww1.microchip.com/downloads/en/DeviceDoc/20002249B.pdf

Signed-off-by: Anshul Dalal <anshulusr@xxxxxxxxx>
---
MAINTAINERS | 7 ++
drivers/iio/dac/Kconfig | 10 ++
drivers/iio/dac/Makefile | 1 +
drivers/iio/dac/mcp4821.c | 207 ++++++++++++++++++++++++++++++++++++++
4 files changed, 225 insertions(+)
create mode 100644 drivers/iio/dac/mcp4821.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 81d5fc0bba68..8d9274c33c6e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13029,6 +13029,13 @@ F: Documentation/ABI/testing/sysfs-bus-iio-potentiometer-mcp4531
F: drivers/iio/potentiometer/mcp4018.c
F: drivers/iio/potentiometer/mcp4531.c

+MCP4821 DAC DRIVER
+M: Anshul Dalal <anshulusr@xxxxxxxxx>
+L: linux-iio@xxxxxxxxxxxxxxx
+S: Maintained
+F: Documentation/devicetree/bindings/iio/dac/microchip,mcp4821.yaml
+F: drivers/iio/dac/mcp4821.c
+
MCR20A IEEE-802.15.4 RADIO DRIVER
M: Stefan Schmidt <stefan@xxxxxxxxxxxxxxxxxx>
L: linux-wpan@xxxxxxxxxxxxxxx
diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
index 93b8be183de6..f5adc364de30 100644
--- a/drivers/iio/dac/Kconfig
+++ b/drivers/iio/dac/Kconfig
@@ -400,6 +400,16 @@ config MCP4728
To compile this driver as a module, choose M here: the module
will be called mcp4728.

+config MCP4821
+ tristate "MCP4801/11/21/02/12/22 DAC driver"
+ depends on SPI
+ help
+ Say yes here to build the driver for the Microchip MCP4801
+ MCP4811, MCP4821, MCP4802, MCP4812 and MCP4822 DAC devices.
+
+ To compile this driver as a module, choose M here: the module
+ will be called mcp4821.
+
config MCP4922
tristate "MCP4902, MCP4912, MCP4922 DAC driver"
depends on SPI
diff --git a/drivers/iio/dac/Makefile b/drivers/iio/dac/Makefile
index 5b2bac900d5a..55bf89739d14 100644
--- a/drivers/iio/dac/Makefile
+++ b/drivers/iio/dac/Makefile
@@ -42,6 +42,7 @@ obj-$(CONFIG_MAX5522) += max5522.o
obj-$(CONFIG_MAX5821) += max5821.o
obj-$(CONFIG_MCP4725) += mcp4725.o
obj-$(CONFIG_MCP4728) += mcp4728.o
+obj-$(CONFIG_MCP4821) += mcp4821.o
obj-$(CONFIG_MCP4922) += mcp4922.o
obj-$(CONFIG_STM32_DAC_CORE) += stm32-dac-core.o
obj-$(CONFIG_STM32_DAC) += stm32-dac.o
diff --git a/drivers/iio/dac/mcp4821.c b/drivers/iio/dac/mcp4821.c
new file mode 100644
index 000000000000..d08acf6b8993
--- /dev/null
+++ b/drivers/iio/dac/mcp4821.c
@@ -0,0 +1,207 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 Anshul Dalal <anshulusr@xxxxxxxxx>
+ *
+ * Driver for Microchip MCP4801, MCP4811, MCP4821, MCP4802, MCP4812 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 <asm/unaligned.h>
+#include <linux/iio/iio.h>
+#include <linux/iio/types.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/spi/spi.h>
+
+#define MCP4821_ACTIVE_MODE BIT(12)
+#define MCP4802_SECOND_CHAN BIT(15)
+#define MCP4821_CHAN_NUM 1
+
+/* 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_MCP4811,
+ ID_MCP4821,
+ ID_MCP4802,
+ ID_MCP4812,
+ ID_MCP4822,
+};
+
+static int mcp4821_chan_count(enum mcp4821_supported_drvice_ids device_id)
+{
+ switch (device_id) {
+ case ID_MCP4801:
+ case ID_MCP4811:
+ case ID_MCP4821:
+ return 1;
+ default:
+ return 2;
+ }
+}
+
+struct mcp4821_state {
+ struct spi_device *spi;
+ struct mutex lock;
+ u16 dac_value[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 = { \
+ .sign = 'u', \
+ .realbits = (resolution), \
+ .storagebits = 16, \
+ .shift = 12 - (resolution), \
+ }, \
+ }
+
+static const struct iio_chan_spec mcp4821_channels[6][2] = {
+ [ID_MCP4801] = { MCP4821_CHAN(0, 8), {} },
+ [ID_MCP4811] = { MCP4821_CHAN(0, 10), {} },
+ [ID_MCP4821] = { MCP4821_CHAN(0, 12), {} },
+ [ID_MCP4802] = { MCP4821_CHAN(0, 8), MCP4821_CHAN(1, 8) },
+ [ID_MCP4812] = { MCP4821_CHAN(0, 10), MCP4821_CHAN(1, 10) },
+ [ID_MCP4822] = { 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);
+ mutex_lock(&state->lock);
+ *val = state->dac_value[chan->channel];
+ mutex_unlock(&state->lock);
+ 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;
+ __be16 write_val;
+ u8 write_buffer[2];
+ int ret;
+ bool is_value_valid = val >= 0 && val < BIT(chan->scan_type.realbits) &&
+ val2 == 0;
+ if (mask == IIO_CHAN_INFO_RAW && is_value_valid) {
+ state = iio_priv(indio_dev);
+
+ write_val = MCP4821_ACTIVE_MODE | val << chan->scan_type.shift;
+ if (chan->channel)
+ write_val |= MCP4802_SECOND_CHAN;
+ put_unaligned_be16(write_val, write_buffer);
+ 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;
+ }
+
+ mutex_lock(&state->lock);
+ state->dac_value[chan->channel] = val;
+ mutex_unlock(&state->lock);
+ return 0;
+ } else {
+ return -EINVAL;
+ }
+}
+
+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 spi_device_id *id;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state));
+ if (indio_dev == NULL) {
+ dev_err(&spi->dev, "Failed to allocate iio device\n");
+ return -ENOMEM;
+ }
+
+ state = iio_priv(indio_dev);
+ spi_set_drvdata(spi, indio_dev);
+ id = spi_get_device_id(spi);
+
+ state->spi = spi;
+ mutex_init(&state->lock);
+
+ indio_dev->name = id->name;
+ indio_dev->info = &mcp4821_info;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->channels = mcp4821_channels[id->driver_data];
+ indio_dev->num_channels = mcp4821_chan_count(id->driver_data);
+ return devm_iio_device_register(&spi->dev, indio_dev);
+}
+
+static const struct spi_device_id mcp4821_id_table[] = {
+ { "mcp4801", ID_MCP4801},
+ { "mcp4811", ID_MCP4811},
+ { "mcp4821", ID_MCP4821},
+ { "mcp4802", ID_MCP4802},
+ { "mcp4812", ID_MCP4812},
+ { "mcp4822", ID_MCP4822},
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(spi, mcp4821_id_table);
+
+static const struct of_device_id mcp4821_of_table[] = {
+ { .compatible = "microchip,mcp4801"},
+ { .compatible = "microchip,mcp4811"},
+ { .compatible = "microchip,mcp4821"},
+ { .compatible = "microchip,mcp4802"},
+ { .compatible = "microchip,mcp4812"},
+ { .compatible = "microchip,mcp4822"},
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mcp4821_of_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@xxxxxxxxx>");
+MODULE_DESCRIPTION("Microchip MCP4821 DAC Driver");
+MODULE_LICENSE("GPL");
--
2.42.1