1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * MAX1241 low-power, 12-bit serial ADC 4 * 5 * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX1240-MAX1241.pdf 6 */ 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 4 17 18 struct max1241 { 19 struct spi_device *spi; 20 struct mutex lock; 21 struct regulator *vref; 22 struct gpio_desc *shutdown; 23 24 __be16 data __aligned(IIO_DMA_MINALIGN); 25 }; 26 27 static const struct iio_chan_spec max1241_channels[] = { 28 { 29 .type = IIO_VOLTAGE, 30 .indexed = 1, 31 .channel = 0, 32 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 33 BIT(IIO_CHAN_INFO_SCALE), 34 }, 35 }; 36 37 static int max1241_read(struct max1241 *adc) 38 { 39 struct spi_transfer xfers[] = { 40 /* 41 * Begin conversion by bringing /CS low for at least 42 * tconv us. 43 */ 44 { 45 .len = 0, 46 .delay.value = 8, 47 .delay.unit = SPI_DELAY_UNIT_USECS, 48 }, 49 /* 50 * Then read two bytes of data in our RX buffer. 51 */ 52 { 53 .rx_buf = &adc->data, 54 .len = 2, 55 }, 56 }; 57 58 return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers)); 59 } 60 61 static int max1241_read_raw(struct iio_dev *indio_dev, 62 struct iio_chan_spec const *chan, 63 int *val, int *val2, long mask) 64 { 65 int ret, vref_uV; 66 struct max1241 *adc = iio_priv(indio_dev); 67 68 switch (mask) { 69 case IIO_CHAN_INFO_RAW: 70 mutex_lock(&adc->lock); 71 72 if (adc->shutdown) { 73 gpiod_set_value(adc->shutdown, 0); 74 udelay(MAX1241_SHUTDOWN_DELAY_USEC); 75 ret = max1241_read(adc); 76 gpiod_set_value(adc->shutdown, 1); 77 } else 78 ret = max1241_read(adc); 79 80 if (ret) { 81 mutex_unlock(&adc->lock); 82 return ret; 83 } 84 85 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK; 86 87 mutex_unlock(&adc->lock); 88 return IIO_VAL_INT; 89 case IIO_CHAN_INFO_SCALE: 90 vref_uV = regulator_get_voltage(adc->vref); 91 92 if (vref_uV < 0) 93 return vref_uV; 94 95 *val = vref_uV / 1000; 96 *val2 = 12; 97 98 return IIO_VAL_FRACTIONAL_LOG2; 99 default: 100 return -EINVAL; 101 } 102 } 103 104 static const struct iio_info max1241_info = { 105 .read_raw = max1241_read_raw, 106 }; 107 108 static void max1241_disable_vref_action(void *data) 109 { 110 struct max1241 *adc = data; 111 struct device *dev = &adc->spi->dev; 112 int err; 113 114 err = regulator_disable(adc->vref); 115 if (err) 116 dev_err(dev, "could not disable vref regulator.\n"); 117 } 118 119 static int max1241_probe(struct spi_device *spi) 120 { 121 struct device *dev = &spi->dev; 122 struct iio_dev *indio_dev; 123 struct max1241 *adc; 124 int ret; 125 126 indio_dev = devm_iio_device_alloc(dev, sizeof(*adc)); 127 if (!indio_dev) 128 return -ENOMEM; 129 130 adc = iio_priv(indio_dev); 131 adc->spi = spi; 132 mutex_init(&adc->lock); 133 134 ret = devm_regulator_get_enable(dev, "vdd"); 135 if (ret) 136 return dev_err_probe(dev, ret, 137 "failed to get/enable vdd regulator\n"); 138 139 adc->vref = devm_regulator_get(dev, "vref"); 140 if (IS_ERR(adc->vref)) 141 return dev_err_probe(dev, PTR_ERR(adc->vref), 142 "failed to get vref regulator\n"); 143 144 ret = regulator_enable(adc->vref); 145 if (ret) 146 return ret; 147 148 ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc); 149 if (ret) { 150 dev_err(dev, "could not set up vref regulator cleanup action\n"); 151 return ret; 152 } 153 154 adc->shutdown = devm_gpiod_get_optional(dev, "shutdown", 155 GPIOD_OUT_HIGH); 156 if (IS_ERR(adc->shutdown)) 157 return dev_err_probe(dev, PTR_ERR(adc->shutdown), 158 "cannot get shutdown gpio\n"); 159 160 if (adc->shutdown) 161 dev_dbg(dev, "shutdown pin passed, low-power mode enabled"); 162 else 163 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled"); 164 165 indio_dev->name = "max1241"; 166 indio_dev->info = &max1241_info; 167 indio_dev->modes = INDIO_DIRECT_MODE; 168 indio_dev->channels = max1241_channels; 169 indio_dev->num_channels = ARRAY_SIZE(max1241_channels); 170 171 return devm_iio_device_register(dev, indio_dev); 172 } 173 174 static const struct spi_device_id max1241_id[] = { 175 { .name = "max1241" }, 176 { } 177 }; 178 MODULE_DEVICE_TABLE(spi, max1241_id); 179 180 static const struct of_device_id max1241_dt_ids[] = { 181 { .compatible = "maxim,max1241" }, 182 { } 183 }; 184 MODULE_DEVICE_TABLE(of, max1241_dt_ids); 185 186 static struct spi_driver max1241_spi_driver = { 187 .driver = { 188 .name = "max1241", 189 .of_match_table = max1241_dt_ids, 190 }, 191 .probe = max1241_probe, 192 .id_table = max1241_id, 193 }; 194 module_spi_driver(max1241_spi_driver); 195 196 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>"); 197 MODULE_DESCRIPTION("MAX1241 ADC driver"); 198 MODULE_LICENSE("GPL v2"); 199