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