1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * iio/adc/max11100.c 4 * Maxim max11100 ADC Driver with IIO interface 5 * 6 * Copyright (C) 2016-17 Renesas Electronics Corporation 7 * Copyright (C) 2016-17 Jacopo Mondi 8 */ 9 #include <linux/delay.h> 10 #include <linux/kernel.h> 11 #include <linux/mod_devicetable.h> 12 #include <linux/module.h> 13 #include <linux/regulator/consumer.h> 14 #include <linux/spi/spi.h> 15 16 #include <linux/iio/iio.h> 17 #include <linux/iio/driver.h> 18 19 /* 20 * LSB is the ADC single digital step 21 * 1 LSB = (vref_mv / 2 ^ 16) 22 * 23 * LSB is used to calculate analog voltage value 24 * from the number of ADC steps count 25 * 26 * Ain = (count * LSB) 27 */ 28 #define MAX11100_LSB_DIV (1 << 16) 29 30 struct max11100_state { 31 struct regulator *vref_reg; 32 struct spi_device *spi; 33 34 /* 35 * DMA (thus cache coherency maintenance) requires the 36 * transfer buffers to live in their own cache lines. 37 */ 38 u8 buffer[3] ____cacheline_aligned; 39 }; 40 41 static const struct iio_chan_spec max11100_channels[] = { 42 { /* [0] */ 43 .type = IIO_VOLTAGE, 44 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 45 BIT(IIO_CHAN_INFO_SCALE), 46 }, 47 }; 48 49 static int max11100_read_single(struct iio_dev *indio_dev, int *val) 50 { 51 int ret; 52 struct max11100_state *state = iio_priv(indio_dev); 53 54 ret = spi_read(state->spi, state->buffer, sizeof(state->buffer)); 55 if (ret) { 56 dev_err(&indio_dev->dev, "SPI transfer failed\n"); 57 return ret; 58 } 59 60 /* the first 8 bits sent out from ADC must be 0s */ 61 if (state->buffer[0]) { 62 dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n"); 63 return -EINVAL; 64 } 65 66 *val = (state->buffer[1] << 8) | state->buffer[2]; 67 68 return 0; 69 } 70 71 static int max11100_read_raw(struct iio_dev *indio_dev, 72 struct iio_chan_spec const *chan, 73 int *val, int *val2, long info) 74 { 75 int ret, vref_uv; 76 struct max11100_state *state = iio_priv(indio_dev); 77 78 switch (info) { 79 case IIO_CHAN_INFO_RAW: 80 ret = max11100_read_single(indio_dev, val); 81 if (ret) 82 return ret; 83 84 return IIO_VAL_INT; 85 86 case IIO_CHAN_INFO_SCALE: 87 vref_uv = regulator_get_voltage(state->vref_reg); 88 if (vref_uv < 0) 89 /* dummy regulator "get_voltage" returns -EINVAL */ 90 return -EINVAL; 91 92 *val = vref_uv / 1000; 93 *val2 = MAX11100_LSB_DIV; 94 return IIO_VAL_FRACTIONAL; 95 } 96 97 return -EINVAL; 98 } 99 100 static const struct iio_info max11100_info = { 101 .read_raw = max11100_read_raw, 102 }; 103 104 static int max11100_probe(struct spi_device *spi) 105 { 106 int ret; 107 struct iio_dev *indio_dev; 108 struct max11100_state *state; 109 110 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state)); 111 if (!indio_dev) 112 return -ENOMEM; 113 114 spi_set_drvdata(spi, indio_dev); 115 116 state = iio_priv(indio_dev); 117 state->spi = spi; 118 119 indio_dev->name = "max11100"; 120 indio_dev->info = &max11100_info; 121 indio_dev->modes = INDIO_DIRECT_MODE; 122 indio_dev->channels = max11100_channels; 123 indio_dev->num_channels = ARRAY_SIZE(max11100_channels); 124 125 state->vref_reg = devm_regulator_get(&spi->dev, "vref"); 126 if (IS_ERR(state->vref_reg)) 127 return PTR_ERR(state->vref_reg); 128 129 ret = regulator_enable(state->vref_reg); 130 if (ret) 131 return ret; 132 133 ret = iio_device_register(indio_dev); 134 if (ret) 135 goto disable_regulator; 136 137 return 0; 138 139 disable_regulator: 140 regulator_disable(state->vref_reg); 141 142 return ret; 143 } 144 145 static int max11100_remove(struct spi_device *spi) 146 { 147 struct iio_dev *indio_dev = spi_get_drvdata(spi); 148 struct max11100_state *state = iio_priv(indio_dev); 149 150 iio_device_unregister(indio_dev); 151 regulator_disable(state->vref_reg); 152 153 return 0; 154 } 155 156 static const struct of_device_id max11100_ids[] = { 157 {.compatible = "maxim,max11100"}, 158 { }, 159 }; 160 MODULE_DEVICE_TABLE(of, max11100_ids); 161 162 static struct spi_driver max11100_driver = { 163 .driver = { 164 .name = "max11100", 165 .of_match_table = max11100_ids, 166 }, 167 .probe = max11100_probe, 168 .remove = max11100_remove, 169 }; 170 171 module_spi_driver(max11100_driver); 172 173 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>"); 174 MODULE_DESCRIPTION("Maxim max11100 ADC Driver"); 175 MODULE_LICENSE("GPL v2"); 176