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 #include <linux/unaligned.h> 16 17 #include <linux/iio/iio.h> 18 #include <linux/iio/driver.h> 19 20 /* 21 * LSB is the ADC single digital step 22 * 1 LSB = (vref_mv / 2 ^ 16) 23 * 24 * LSB is used to calculate analog voltage value 25 * from the number of ADC steps count 26 * 27 * Ain = (count * LSB) 28 */ 29 #define MAX11100_LSB_DIV (1 << 16) 30 31 struct max11100_state { 32 struct regulator *vref_reg; 33 struct spi_device *spi; 34 35 /* 36 * DMA (thus cache coherency maintenance) may require the 37 * transfer buffers to live in their own cache lines. 38 */ 39 u8 buffer[3] __aligned(IIO_DMA_MINALIGN); 40 }; 41 42 static const struct iio_chan_spec max11100_channels[] = { 43 { /* [0] */ 44 .type = IIO_VOLTAGE, 45 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | 46 BIT(IIO_CHAN_INFO_SCALE), 47 }, 48 }; 49 50 static int max11100_read_single(struct iio_dev *indio_dev, int *val) 51 { 52 int ret; 53 struct max11100_state *state = iio_priv(indio_dev); 54 55 ret = spi_read(state->spi, state->buffer, sizeof(state->buffer)); 56 if (ret) { 57 dev_err(&indio_dev->dev, "SPI transfer failed\n"); 58 return ret; 59 } 60 61 /* the first 8 bits sent out from ADC must be 0s */ 62 if (state->buffer[0]) { 63 dev_err(&indio_dev->dev, "Invalid value: buffer[0] != 0\n"); 64 return -EINVAL; 65 } 66 67 *val = get_unaligned_be16(&state->buffer[1]); 68 69 return 0; 70 } 71 72 static int max11100_read_raw(struct iio_dev *indio_dev, 73 struct iio_chan_spec const *chan, 74 int *val, int *val2, long info) 75 { 76 int ret, vref_uv; 77 struct max11100_state *state = iio_priv(indio_dev); 78 79 switch (info) { 80 case IIO_CHAN_INFO_RAW: 81 ret = max11100_read_single(indio_dev, val); 82 if (ret) 83 return ret; 84 85 return IIO_VAL_INT; 86 87 case IIO_CHAN_INFO_SCALE: 88 vref_uv = regulator_get_voltage(state->vref_reg); 89 if (vref_uv < 0) 90 /* dummy regulator "get_voltage" returns -EINVAL */ 91 return -EINVAL; 92 93 *val = vref_uv / 1000; 94 *val2 = MAX11100_LSB_DIV; 95 return IIO_VAL_FRACTIONAL; 96 } 97 98 return -EINVAL; 99 } 100 101 static const struct iio_info max11100_info = { 102 .read_raw = max11100_read_raw, 103 }; 104 105 static void max11100_regulator_disable(void *reg) 106 { 107 regulator_disable(reg); 108 } 109 110 static int max11100_probe(struct spi_device *spi) 111 { 112 int ret; 113 struct iio_dev *indio_dev; 114 struct max11100_state *state; 115 116 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*state)); 117 if (!indio_dev) 118 return -ENOMEM; 119 120 state = iio_priv(indio_dev); 121 state->spi = spi; 122 123 indio_dev->name = "max11100"; 124 indio_dev->info = &max11100_info; 125 indio_dev->modes = INDIO_DIRECT_MODE; 126 indio_dev->channels = max11100_channels; 127 indio_dev->num_channels = ARRAY_SIZE(max11100_channels); 128 129 state->vref_reg = devm_regulator_get(&spi->dev, "vref"); 130 if (IS_ERR(state->vref_reg)) 131 return PTR_ERR(state->vref_reg); 132 133 ret = regulator_enable(state->vref_reg); 134 if (ret) 135 return ret; 136 137 ret = devm_add_action_or_reset(&spi->dev, max11100_regulator_disable, 138 state->vref_reg); 139 if (ret) 140 return ret; 141 142 return devm_iio_device_register(&spi->dev, indio_dev); 143 } 144 145 static const struct of_device_id max11100_ids[] = { 146 { .compatible = "maxim,max11100" }, 147 { } 148 }; 149 MODULE_DEVICE_TABLE(of, max11100_ids); 150 151 static struct spi_driver max11100_driver = { 152 .driver = { 153 .name = "max11100", 154 .of_match_table = max11100_ids, 155 }, 156 .probe = max11100_probe, 157 }; 158 159 module_spi_driver(max11100_driver); 160 161 MODULE_AUTHOR("Jacopo Mondi <jacopo@jmondi.org>"); 162 MODULE_DESCRIPTION("Maxim max11100 ADC Driver"); 163 MODULE_LICENSE("GPL v2"); 164