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 enum max1241_id { 19 max1241, 20 }; 21 22 struct max1241 { 23 struct spi_device *spi; 24 struct mutex lock; 25 struct regulator *vdd; 26 struct regulator *vref; 27 struct gpio_desc *shutdown; 28 29 __be16 data ____cacheline_aligned; 30 }; 31 32 static const struct iio_chan_spec max1241_channels[] = { 33 { 34 .type = IIO_VOLTAGE, 35 .indexed = 1, 36 .channel = 0, 37 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 38 BIT(IIO_CHAN_INFO_SCALE), 39 }, 40 }; 41 42 static int max1241_read(struct max1241 *adc) 43 { 44 struct spi_transfer xfers[] = { 45 /* 46 * Begin conversion by bringing /CS low for at least 47 * tconv us. 48 */ 49 { 50 .len = 0, 51 .delay.value = 8, 52 .delay.unit = SPI_DELAY_UNIT_USECS, 53 }, 54 /* 55 * Then read two bytes of data in our RX buffer. 56 */ 57 { 58 .rx_buf = &adc->data, 59 .len = 2, 60 }, 61 }; 62 63 return spi_sync_transfer(adc->spi, xfers, ARRAY_SIZE(xfers)); 64 } 65 66 static int max1241_read_raw(struct iio_dev *indio_dev, 67 struct iio_chan_spec const *chan, 68 int *val, int *val2, long mask) 69 { 70 int ret, vref_uV; 71 struct max1241 *adc = iio_priv(indio_dev); 72 73 switch (mask) { 74 case IIO_CHAN_INFO_RAW: 75 mutex_lock(&adc->lock); 76 77 if (adc->shutdown) { 78 gpiod_set_value(adc->shutdown, 0); 79 udelay(MAX1241_SHUTDOWN_DELAY_USEC); 80 ret = max1241_read(adc); 81 gpiod_set_value(adc->shutdown, 1); 82 } else 83 ret = max1241_read(adc); 84 85 if (ret) { 86 mutex_unlock(&adc->lock); 87 return ret; 88 } 89 90 *val = (be16_to_cpu(adc->data) >> 3) & MAX1241_VAL_MASK; 91 92 mutex_unlock(&adc->lock); 93 return IIO_VAL_INT; 94 case IIO_CHAN_INFO_SCALE: 95 vref_uV = regulator_get_voltage(adc->vref); 96 97 if (vref_uV < 0) 98 return vref_uV; 99 100 *val = vref_uV / 1000; 101 *val2 = 12; 102 103 return IIO_VAL_FRACTIONAL_LOG2; 104 default: 105 return -EINVAL; 106 } 107 } 108 109 static const struct iio_info max1241_info = { 110 .read_raw = max1241_read_raw, 111 }; 112 113 static void max1241_disable_vdd_action(void *data) 114 { 115 struct max1241 *adc = data; 116 struct device *dev = &adc->spi->dev; 117 int err; 118 119 err = regulator_disable(adc->vdd); 120 if (err) 121 dev_err(dev, "could not disable vdd regulator.\n"); 122 } 123 124 static void max1241_disable_vref_action(void *data) 125 { 126 struct max1241 *adc = data; 127 struct device *dev = &adc->spi->dev; 128 int err; 129 130 err = regulator_disable(adc->vref); 131 if (err) 132 dev_err(dev, "could not disable vref regulator.\n"); 133 } 134 135 static int max1241_probe(struct spi_device *spi) 136 { 137 struct device *dev = &spi->dev; 138 struct iio_dev *indio_dev; 139 struct max1241 *adc; 140 int ret; 141 142 indio_dev = devm_iio_device_alloc(dev, sizeof(*adc)); 143 if (!indio_dev) 144 return -ENOMEM; 145 146 adc = iio_priv(indio_dev); 147 adc->spi = spi; 148 mutex_init(&adc->lock); 149 150 spi_set_drvdata(spi, indio_dev); 151 152 adc->vdd = devm_regulator_get(dev, "vdd"); 153 if (IS_ERR(adc->vdd)) { 154 dev_err(dev, "failed to get vdd regulator\n"); 155 return PTR_ERR(adc->vdd); 156 } 157 158 ret = regulator_enable(adc->vdd); 159 if (ret) 160 return ret; 161 162 ret = devm_add_action_or_reset(dev, max1241_disable_vdd_action, adc); 163 if (ret) { 164 dev_err(dev, "could not set up vdd regulator cleanup action\n"); 165 return ret; 166 } 167 168 adc->vref = devm_regulator_get(dev, "vref"); 169 if (IS_ERR(adc->vref)) { 170 dev_err(dev, "failed to get vref regulator\n"); 171 return PTR_ERR(adc->vref); 172 } 173 174 ret = regulator_enable(adc->vref); 175 if (ret) 176 return ret; 177 178 ret = devm_add_action_or_reset(dev, max1241_disable_vref_action, adc); 179 if (ret) { 180 dev_err(dev, "could not set up vref regulator cleanup action\n"); 181 return ret; 182 } 183 184 adc->shutdown = devm_gpiod_get_optional(dev, "shutdown", 185 GPIOD_OUT_HIGH); 186 if (IS_ERR(adc->shutdown)) 187 return PTR_ERR(adc->shutdown); 188 189 if (adc->shutdown) 190 dev_dbg(dev, "shutdown pin passed, low-power mode enabled"); 191 else 192 dev_dbg(dev, "no shutdown pin passed, low-power mode disabled"); 193 194 indio_dev->name = spi_get_device_id(spi)->name; 195 indio_dev->dev.parent = dev; 196 indio_dev->info = &max1241_info; 197 indio_dev->modes = INDIO_DIRECT_MODE; 198 indio_dev->channels = max1241_channels; 199 indio_dev->num_channels = ARRAY_SIZE(max1241_channels); 200 201 return devm_iio_device_register(dev, indio_dev); 202 } 203 204 static const struct spi_device_id max1241_id[] = { 205 { "max1241", max1241 }, 206 {} 207 }; 208 209 static const struct of_device_id max1241_dt_ids[] = { 210 { .compatible = "maxim,max1241" }, 211 {} 212 }; 213 MODULE_DEVICE_TABLE(of, max1241_dt_ids); 214 215 static struct spi_driver max1241_spi_driver = { 216 .driver = { 217 .name = "max1241", 218 .of_match_table = max1241_dt_ids, 219 }, 220 .probe = max1241_probe, 221 .id_table = max1241_id, 222 }; 223 module_spi_driver(max1241_spi_driver); 224 225 MODULE_AUTHOR("Alexandru Lazar <alazar@startmail.com>"); 226 MODULE_DESCRIPTION("MAX1241 ADC driver"); 227 MODULE_LICENSE("GPL v2"); 228