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1// SPDX-License-Identifier: GPL-2.0-only2/*3 * MAX1241 low-power, 12-bit serial ADC4 *5 * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf6 */7 8#include <linux/delay.h>9#include <linux/gpio/consumer.h>10#include <linux/iio/iio.h>11#include <linux/module.h>12#include <linux/regulator/consumer.h>13#include <linux/spi/spi.h>14 15#define MAX1241_VAL_MASK GENMASK(11, 0)16#define MAX1241_SHUTDOWN_DELAY_USEC 417 18enum max1241_id {19 max1241,20};21 22struct max1241 {23 struct spi_device *spi;24 struct mutex lock;25 struct regulator *vref;26 struct gpio_desc *shutdown;27 28 __be16 data __aligned(IIO_DMA_MINALIGN);29};30 31static const struct iio_chan_spec max1241_channels[] = {32 {33 .type = IIO_VOLTAGE,34 .indexed = 1,35 .channel = 0,36 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |37 BIT(IIO_CHAN_INFO_SCALE),38 },39};40 41static int max1241_read(struct max1241 *adc)42{43 struct spi_transfer xfers[] = {44 /*45 * Begin conversion by bringing /CS low for at least46 * tconv us.47 */48 {49 .len = 0,50 .delay.value = 8,51 .delay.unit = SPI_DELAY_UNIT_USECS,52 },53 /*54 * Then read two bytes of data in our RX buffer.55 */56 {57 .rx_buf = &adc->data,58 .len = 2,59 },60 };61 62 return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers));63}64 65static int max1241_read_raw(struct iio_dev *indio_dev,66 struct iio_chan_spec const *chan,67 int *val, int *val2, long mask)68{69 int ret, vref_uV;70 struct max1241 *adc = iio_priv(indio_dev);71 72 switch (mask) {73 case IIO_CHAN_INFO_RAW:74 mutex_lock(&adc->lock);75 76 if (adc->shutdown) {77 gpiod_set_value(adc->shutdown, 0);78 udelay(MAX1241_SHUTDOWN_DELAY_USEC);79 ret = max1241_read(adc);80 gpiod_set_value(adc->shutdown, 1);81 } else82 ret = max1241_read(adc);83 84 if (ret) {85 mutex_unlock(&adc->lock);86 return ret;87 }88 89 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK;90 91 mutex_unlock(&adc->lock);92 return IIO_VAL_INT;93 case IIO_CHAN_INFO_SCALE:94 vref_uV = regulator_get_voltage(adc->vref);95 96 if (vref_uV < 0)97 return vref_uV;98 99 *val = vref_uV / 1000;100 *val2 = 12;101 102 return IIO_VAL_FRACTIONAL_LOG2;103 default:104 return -EINVAL;105 }106}107 108static const struct iio_info max1241_info = {109 .read_raw = max1241_read_raw,110};111 112static void max1241_disable_vref_action(void *data)113{114 struct max1241 *adc = data;115 struct device *dev = &adc->spi->dev;116 int err;117 118 err = regulator_disable(adc->vref);119 if (err)120 dev_err(dev, "could not disable vref regulator.\n");121}122 123static int max1241_probe(struct spi_device *spi)124{125 struct device *dev = &spi->dev;126 struct iio_dev *indio_dev;127 struct max1241 *adc;128 int ret;129 130 indio_dev = devm_iio_device_alloc(dev, sizeof(*adc));131 if (!indio_dev)132 return -ENOMEM;133 134 adc = iio_priv(indio_dev);135 adc->spi = spi;136 mutex_init(&adc->lock);137 138 ret = devm_regulator_get_enable(dev, "vdd");139 if (ret)140 return dev_err_probe(dev, ret,141 "failed to get/enable vdd regulator\n");142 143 adc->vref = devm_regulator_get(dev, "vref");144 if (IS_ERR(adc->vref))145 return dev_err_probe(dev, PTR_ERR(adc->vref),146 "failed to get vref regulator\n");147 148 ret = regulator_enable(adc->vref);149 if (ret)150 return ret;151 152 ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc);153 if (ret) {154 dev_err(dev, "could not set up vref regulator cleanup action\n");155 return ret;156 }157 158 adc->shutdown = devm_gpiod_get_optional(dev, "shutdown",159 GPIOD_OUT_HIGH);160 if (IS_ERR(adc->shutdown))161 return dev_err_probe(dev, PTR_ERR(adc->shutdown),162 "cannot get shutdown gpio\n");163 164 if (adc->shutdown)165 dev_dbg(dev, "shutdown pin passed, low-power mode enabled");166 else167 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled");168 169 indio_dev->name = spi_get_device_id(spi)->name;170 indio_dev->info = &max1241_info;171 indio_dev->modes = INDIO_DIRECT_MODE;172 indio_dev->channels = max1241_channels;173 indio_dev->num_channels = ARRAY_SIZE(max1241_channels);174 175 return devm_iio_device_register(dev, indio_dev);176}177 178static const struct spi_device_id max1241_id[] = {179 { "max1241", max1241 },180 { }181};182 183static const struct of_device_id max1241_dt_ids[] = {184 { .compatible = "maxim,max1241" },185 { }186};187MODULE_DEVICE_TABLE(of, max1241_dt_ids);188 189static struct spi_driver max1241_spi_driver = {190 .driver = {191 .name = "max1241",192 .of_match_table = max1241_dt_ids,193 },194 .probe = max1241_probe,195 .id_table = max1241_id,196};197module_spi_driver(max1241_spi_driver);198 199MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>");200MODULE_DESCRIPTION("MAX1241 ADC driver");201MODULE_LICENSE("GPL v2");202