[PATCH v2 1/3] iio: adc: add support for mcp3911

From: Marcus Folkesson
Date: Tue Jul 24 2018 - 14:52:59 EST

MCP3911 is a dual channel Analog Front End (AFE) containing two
synchronous sampling delta-sigma Analog-to-Digital Converters (ADC).

Signed-off-by: Marcus Folkesson <marcus.folkesson@xxxxxxxxx>
Signed-off-by: Kent Gustavsson <kent@xxxxxxxxxx>
---

Notes:
v2:
- cleanups and bugfixes (thanks Peter Meerwald-Stadler)
- drop hardware gain
- use the presence or lack of regulator to indicate if we go for internal or external voltage reference
- do not store device node in private struct
- drop support to set width in devicetree
- use the presence or lack of clock to indicate if we go for internal or external clock

drivers/iio/adc/Kconfig | 10 ++
drivers/iio/adc/Makefile | 1 +
drivers/iio/adc/mcp3911.c | 366 ++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 377 insertions(+)
create mode 100644 drivers/iio/adc/mcp3911.c

diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
index 15606f237480..f9a41fa96fcc 100644
--- a/drivers/iio/adc/Kconfig
+++ b/drivers/iio/adc/Kconfig
@@ -501,6 +501,16 @@ config MCP3422
This driver can also be built as a module. If so, the module will be
called mcp3422.

+config MCP3911
+ tristate "Microchip Technology MCP3911 driver"
+ depends on SPI
+ help
+ Say yes here to build support for Microchip Technology's MCP3911
+ analog to digital converter.
+
+ This driver can also be built as a module. If so, the module will be
+ called mcp3911.
+
config MEDIATEK_MT6577_AUXADC
tristate "MediaTek AUXADC driver"
depends on ARCH_MEDIATEK || COMPILE_TEST
diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
index 28a9423997f3..3cfebfff7d26 100644
--- a/drivers/iio/adc/Makefile
+++ b/drivers/iio/adc/Makefile
@@ -47,6 +47,7 @@ obj-$(CONFIG_MAX1363) += max1363.o
obj-$(CONFIG_MAX9611) += max9611.o
obj-$(CONFIG_MCP320X) += mcp320x.o
obj-$(CONFIG_MCP3422) += mcp3422.o
+obj-$(CONFIG_MCP3911) += mcp3911.o
obj-$(CONFIG_MEDIATEK_MT6577_AUXADC) += mt6577_auxadc.o
obj-$(CONFIG_MEN_Z188_ADC) += men_z188_adc.o
obj-$(CONFIG_MESON_SARADC) += meson_saradc.o
diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
new file mode 100644
index 000000000000..29aa39930ead
--- /dev/null
+++ b/drivers/iio/adc/mcp3911.c
@@ -0,0 +1,366 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Microchip MCP3911, Two-channel Analog Front End
+ *
+ * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@xxxxxxxxx>
+ * Copyright (C) 2018 Kent Gustavsson <kent@xxxxxxxxxx>
+ *
+ */
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/iio/iio.h>
+#include <linux/module.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+
+#define MCP3911_REG_CHANNEL0 0x00
+#define MCP3911_REG_CHANNEL1 0x03
+#define MCP3911_REG_MOD 0x06
+#define MCP3911_REG_PHASE 0x07
+#define MCP3911_REG_GAIN 0x09
+
+#define MCP3911_REG_STATUSCOM 0x0a
+#define MCP3911_STATUSCOM_CH1_24WIDTH BIT(4)
+#define MCP3911_STATUSCOM_CH0_24WIDTH BIT(3)
+#define MCP3911_STATUSCOM_EN_OFFCAL BIT(2)
+#define MCP3911_STATUSCOM_EN_GAINCAL BIT(1)
+
+#define MCP3911_REG_CONFIG 0x0c
+#define MCP3911_CONFIG_CLKEXT BIT(1)
+#define MCP3911_CONFIG_VREFEXT BIT(2)
+
+#define MCP3911_REG_OFFCAL_CH0 0x0e
+#define MCP3911_REG_GAINCAL_CH0 0x11
+#define MCP3911_REG_OFFCAL_CH1 0x14
+#define MCP3911_REG_GAINCAL_CH1 0x17
+#define MCP3911_REG_VREFCAL 0x1a
+
+#define MCP3911_CHANNEL(x) (MCP3911_REG_CHANNEL0 + x * 3)
+#define MCP3911_OFFCAL(x) (MCP3911_REG_OFFCAL_CH0 + x * 6)
+
+/* Internal voltage reference in uV */
+#define MCP3911_INT_VREF_UV 1200000
+
+#define MCP3911_REG_READ(reg, id) ((((reg) << 1) | ((id) << 5) | (1 << 0)) & 0xff)
+#define MCP3911_REG_WRITE(reg, id) ((((reg) << 1) | ((id) << 5) | (0 << 0)) & 0xff)
+
+#define MCP3911_NUM_CHANNELS 2
+
+struct mcp3911 {
+ struct spi_device *spi;
+ struct mutex lock;
+ struct regulator *vref;
+ struct clk *adc_clk;
+ u32 dev_addr;
+};
+
+static int mcp3911_read(struct mcp3911 *adc, u8 reg, u32 *val, u8 len)
+{
+ int ret;
+
+ reg = MCP3911_REG_READ(reg, adc->dev_addr);
+ ret = spi_write_then_read(adc->spi, &reg, 1, val, len);
+ if (ret < 0)
+ return ret;
+
+ be32_to_cpus(val);
+ *val >>= ((4 - len) * 8);
+ dev_dbg(&adc->spi->dev, "reading 0x%x from register 0x%x\n", *val,
+ reg>>1);
+ return ret;
+}
+
+static int mcp3911_write(struct mcp3911 *adc, u8 reg, u32 val, u8 len)
+{
+ dev_dbg(&adc->spi->dev, "writing 0x%x to register 0x%x\n", val, reg);
+
+ val <<= (3 - len) * 8;
+ cpu_to_be32s(&val);
+ val |= MCP3911_REG_WRITE(reg, adc->dev_addr);
+
+ return spi_write(adc->spi, &val, len+1);
+}
+
+static int mcp3911_update(struct mcp3911 *adc, u8 reg, u32 mask,
+ u32 val, u8 len)
+{
+ u32 tmp;
+ int ret;
+
+ ret = mcp3911_read(adc, reg, &tmp, len);
+ if (ret)
+ return ret;
+
+ val &= mask;
+ val |= tmp & ~mask;
+ return mcp3911_write(adc, reg, val, len);
+}
+
+static int mcp3911_read_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *channel, int *val,
+ int *val2, long mask)
+{
+ struct mcp3911 *adc = iio_priv(indio_dev);
+ int ret = -EINVAL;
+
+ mutex_lock(&adc->lock);
+ switch (mask) {
+ case IIO_CHAN_INFO_RAW:
+ ret = mcp3911_read(adc,
+ MCP3911_CHANNEL(channel->channel), val, 3);
+ if (ret)
+ goto out;
+
+ ret = IIO_VAL_INT;
+ break;
+
+ case IIO_CHAN_INFO_OFFSET:
+ ret = mcp3911_read(adc,
+ MCP3911_OFFCAL(channel->channel), val, 3);
+ if (ret)
+ goto out;
+
+ ret = IIO_VAL_INT;
+ break;
+
+ case IIO_CHAN_INFO_SCALE:
+ if (adc->vref) {
+ ret = regulator_get_voltage(adc->vref);
+ if (ret < 0) {
+ dev_err(indio_dev->dev.parent,
+ "failed to get vref voltage: %d\n",
+ ret);
+ goto out;
+ }
+
+ *val = ret / 1000;
+ } else {
+ *val = MCP3911_INT_VREF_UV;
+ }
+
+ *val2 = 24;
+ ret = IIO_VAL_FRACTIONAL_LOG2;
+ break;
+ }
+
+out:
+ mutex_unlock(&adc->lock);
+ return ret;
+}
+
+static int mcp3911_write_raw(struct iio_dev *indio_dev,
+ struct iio_chan_spec const *channel, int val,
+ int val2, long mask)
+{
+ struct mcp3911 *adc = iio_priv(indio_dev);
+ int ret = -EINVAL;
+
+ mutex_lock(&adc->lock);
+ switch (mask) {
+ case IIO_CHAN_INFO_OFFSET:
+ if (val2 != 0) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* Write offset */
+ ret = mcp3911_write(adc, MCP3911_OFFCAL(channel->channel), val,
+ 3);
+ if (ret)
+ goto out;
+
+ /* Enable offset*/
+ ret = mcp3911_update(adc, MCP3911_REG_STATUSCOM,
+ MCP3911_STATUSCOM_EN_OFFCAL,
+ MCP3911_STATUSCOM_EN_OFFCAL, 2);
+ break;
+ }
+
+out:
+ mutex_unlock(&adc->lock);
+ return ret;
+}
+
+#define MCP3911_CHAN(idx) { \
+ .type = IIO_VOLTAGE, \
+ .indexed = 1, \
+ .channel = idx, \
+ .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | \
+ BIT(IIO_CHAN_INFO_OFFSET) | \
+ BIT(IIO_CHAN_INFO_SCALE), \
+}
+
+static const struct iio_chan_spec mcp3911_channels[] = {
+ MCP3911_CHAN(0),
+ MCP3911_CHAN(1),
+};
+
+static const struct iio_info mcp3911_info = {
+ .read_raw = mcp3911_read_raw,
+ .write_raw = mcp3911_write_raw,
+};
+
+static int mcp3911_config(struct mcp3911 *adc, struct device_node *of_node)
+{
+ u32 configreg;
+ int ret;
+
+ of_property_read_u32(of_node, "device-addr", &adc->dev_addr);
+ if (adc->dev_addr > 3) {
+ dev_err(&adc->spi->dev,
+ "invalid device address (%i). Must be in range 0-3.\n",
+ adc->dev_addr);
+ return -EINVAL;
+ }
+ dev_dbg(&adc->spi->dev, "use device address %i\n", adc->dev_addr);
+
+ ret = mcp3911_read(adc, MCP3911_REG_CONFIG, &configreg, 2);
+ if (ret)
+ return ret;
+
+ if (adc->vref) {
+ dev_dbg(&adc->spi->dev, "use external voltage reference\n");
+ configreg |= MCP3911_CONFIG_VREFEXT;
+
+ } else {
+ dev_dbg(&adc->spi->dev, "use internal voltage reference (1.2V)\n");
+ configreg &= ~MCP3911_CONFIG_VREFEXT;
+ }
+
+ if (adc->adc_clk) {
+ dev_dbg(&adc->spi->dev, "use external clock as clocksource\n");
+ configreg |= MCP3911_CONFIG_CLKEXT;
+ } else {
+ dev_dbg(&adc->spi->dev, "use crystal oscillator as clocksource\n");
+ configreg &= ~MCP3911_CONFIG_CLKEXT;
+ }
+
+ return mcp3911_write(adc, MCP3911_REG_CONFIG, configreg, 2);
+}
+
+static int mcp3911_probe(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev;
+ struct mcp3911 *adc;
+ int ret;
+
+ indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*adc));
+ if (!indio_dev)
+ return -ENOMEM;
+
+ adc = iio_priv(indio_dev);
+ adc->spi = spi;
+
+ adc->vref = devm_regulator_get_optional(&adc->spi->dev, "vref");
+ if (IS_ERR(adc->vref)) {
+
+ if (PTR_ERR(adc->vref) == -ENODEV) {
+ adc->vref = NULL;
+ } else {
+ dev_err(&adc->spi->dev,
+ "failed to get regulator (%ld)\n",
+ PTR_ERR(adc->vref));
+ return PTR_ERR(adc->vref);
+ }
+
+ } else {
+ ret = regulator_enable(adc->vref);
+ if (ret)
+ return ret;
+ }
+
+ adc->adc_clk = devm_clk_get(&adc->spi->dev, "adc_clk");
+ if (IS_ERR(adc->adc_clk)) {
+ if (PTR_ERR(adc->adc_clk) == -ENOENT) {
+ adc->adc_clk = NULL;
+ } else {
+ dev_err(&adc->spi->dev,
+ "failed to get adc clk (%ld)\n",
+ PTR_ERR(adc->adc_clk));
+ ret = PTR_ERR(adc->adc_clk);
+ goto reg_disable;
+ }
+ } else {
+ ret = clk_prepare_enable(adc->adc_clk);
+ if (ret < 0) {
+ dev_err(&adc->spi->dev,
+ "Failed to enable adc_clk: %d\n", ret);
+ goto reg_disable;
+ }
+ }
+
+ ret = mcp3911_config(adc, spi->dev.of_node);
+ if (ret)
+ goto clk_disable;
+
+ indio_dev->dev.parent = &spi->dev;
+ indio_dev->dev.of_node = spi->dev.of_node;
+ indio_dev->name = spi_get_device_id(spi)->name;
+ indio_dev->modes = INDIO_DIRECT_MODE;
+ indio_dev->info = &mcp3911_info;
+ spi_set_drvdata(spi, indio_dev);
+
+ indio_dev->channels = mcp3911_channels;
+ indio_dev->num_channels = ARRAY_SIZE(mcp3911_channels);
+
+ mutex_init(&adc->lock);
+
+ ret = iio_device_register(indio_dev);
+ if (ret)
+ goto clk_disable;
+
+ return ret;
+
+clk_disable:
+ if (adc->adc_clk)
+ clk_disable_unprepare(adc->adc_clk);
+reg_disable:
+ if (adc->vref)
+ regulator_disable(adc->vref);
+
+ return ret;
+}
+
+static int mcp3911_remove(struct spi_device *spi)
+{
+ struct iio_dev *indio_dev = spi_get_drvdata(spi);
+ struct mcp3911 *adc = iio_priv(indio_dev);
+
+ iio_device_unregister(indio_dev);
+
+ if (adc->vref)
+ regulator_disable(adc->vref);
+
+ return 0;
+}
+
+#if defined(CONFIG_OF)
+static const struct of_device_id mcp3911_dt_ids[] = {
+ { .compatible = "microchip,mcp3911" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, mcp3911_dt_ids);
+#endif
+
+static const struct spi_device_id mcp3911_id[] = {
+ { "mcp3911", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(spi, mcp3911_id);
+
+static struct spi_driver mcp3911_driver = {
+ .driver = {
+ .name = "mcp3911",
+ .of_match_table = of_match_ptr(mcp3911_dt_ids),
+ },
+ .probe = mcp3911_probe,
+ .remove = mcp3911_remove,
+ .id_table = mcp3911_id,
+};
+module_spi_driver(mcp3911_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@xxxxxxxxx>");
+MODULE_AUTHOR("Kent Gustavsson <kent@xxxxxxxxxx>");
+MODULE_DESCRIPTION("Microchip Technology MCP3911");
+MODULE_LICENSE("GPL v2");
--
2.11.0.rc2