1 /* 2 * iio/adc/max11100.c 3 * Maxim max11100 ADC Driver with IIO interface 4 * 5 * Copyright (C) 2016-17 Renesas Electronics Corporation 6 * Copyright (C) 2016-17 Jacopo Mondi 7 * 8 * This program is free software; you can redistribute it and/or modify 9 * it under the terms of the GNU General Public License version 2 as 10 * published by the Free Software Foundation. 11 */ 12 #include <linux/delay.h> 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/regulator/consumer.h> 16 #include <linux/spi/spi.h> 17 18 #include <linux/iio/iio.h> 19 #include <linux/iio/driver.h> 20 21 /* 22 * LSB is the ADC single digital step 23 * 1 LSB = (vref_mv / 2 ^ 16) 24 * 25 * LSB is used to calculate analog voltage value 26 * from the number of ADC steps count 27 * 28 * Ain = (count * LSB) 29 */ 30 #define MAX11100_LSB_DIV (1 << 16) 31 32 struct max11100_state { 33 struct regulator *vref_reg; 34 struct spi_device *spi; 35 36 /* 37 * DMA (thus cache coherency maintenance) requires the 38 * transfer buffers to live in their own cache lines. 39 */ 40 u8 buffer[3] ____cacheline_aligned; 41 }; 42 43 static struct iio_chan_spec max11100_channels[] = { 44 { /* [0] */ 45 .type = IIO_VOLTAGE, 46 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 47 BIT(IIO_CHAN_INFO_SCALE), 48 }, 49 }; 50 51 static int max11100_read_single(struct iio_dev *indio_dev, int *val) 52 { 53 int ret; 54 struct max11100_state *state = iio_priv(indio_dev); 55 56 ret = spi_read(state->spi, state->buffer, sizeof(state->buffer)); 57 if (ret) { 58 dev_err(&indio_dev->dev, "SPI transfer failed\n"); 59 return ret; 60 } 61 62 /* the first 8 bits sent out from ADC must be 0s */ 63 if (state->buffer[0]) { 64 dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n"); 65 return -EINVAL; 66 } 67 68 *val = (state->buffer[1] << 8) | state->buffer[2]; 69 70 return 0; 71 } 72 73 static int max11100_read_raw(struct iio_dev *indio_dev, 74 struct iio_chan_spec const *chan, 75 int *val, int *val2, long info) 76 { 77 int ret, vref_uv; 78 struct max11100_state *state = iio_priv(indio_dev); 79 80 switch (info) { 81 case IIO_CHAN_INFO_RAW: 82 ret = max11100_read_single(indio_dev, val); 83 if (ret) 84 return ret; 85 86 return IIO_VAL_INT; 87 88 case IIO_CHAN_INFO_SCALE: 89 vref_uv = regulator_get_voltage(state->vref_reg); 90 if (vref_uv < 0) 91 /* dummy regulator "get_voltage" returns -EINVAL */ 92 return -EINVAL; 93 94 *val = vref_uv / 1000; 95 *val2 = MAX11100_LSB_DIV; 96 return IIO_VAL_FRACTIONAL; 97 } 98 99 return -EINVAL; 100 } 101 102 static const struct iio_info max11100_info = { 103 .driver_module = THIS_MODULE, 104 .read_raw = max11100_read_raw, 105 }; 106 107 static int max11100_probe(struct spi_device *spi) 108 { 109 int ret; 110 struct iio_dev *indio_dev; 111 struct max11100_state *state; 112 113 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state)); 114 if (!indio_dev) 115 return -ENOMEM; 116 117 spi_set_drvdata(spi, indio_dev); 118 119 state = iio_priv(indio_dev); 120 state->spi = spi; 121 122 indio_dev->dev.parent = &spi->dev; 123 indio_dev->dev.of_node = spi->dev.of_node; 124 indio_dev->name = "max11100"; 125 indio_dev->info = &max11100_info; 126 indio_dev->modes = INDIO_DIRECT_MODE; 127 indio_dev->channels = max11100_channels; 128 indio_dev->num_channels = ARRAY_SIZE(max11100_channels); 129 130 state->vref_reg = devm_regulator_get(&spi->dev, "vref"); 131 if (IS_ERR(state->vref_reg)) 132 return PTR_ERR(state->vref_reg); 133 134 ret = regulator_enable(state->vref_reg); 135 if (ret) 136 return ret; 137 138 ret = iio_device_register(indio_dev); 139 if (ret) 140 goto disable_regulator; 141 142 return 0; 143 144 disable_regulator: 145 regulator_disable(state->vref_reg); 146 147 return ret; 148 } 149 150 static int max11100_remove(struct spi_device *spi) 151 { 152 struct iio_dev *indio_dev = spi_get_drvdata(spi); 153 struct max11100_state *state = iio_priv(indio_dev); 154 155 iio_device_unregister(indio_dev); 156 regulator_disable(state->vref_reg); 157 158 return 0; 159 } 160 161 static const struct of_device_id max11100_ids[] = { 162 {.compatible = "maxim,max11100"}, 163 { }, 164 }; 165 MODULE_DEVICE_TABLE(of, max11100_ids); 166 167 static struct spi_driver max11100_driver = { 168 .driver = { 169 .name = "max11100", 170 .of_match_table = of_match_ptr(max11100_ids), 171 }, 172 .probe = max11100_probe, 173 .remove = max11100_remove, 174 }; 175 176 module_spi_driver(max11100_driver); 177 178 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>"); 179 MODULE_DESCRIPTION("Maxim max11100 ADC Driver"); 180 MODULE_LICENSE("GPL v2"); 181