drivers/iio/temperature/maxim_thermocouple.c

   1 /*
   2  * maxim_thermocouple.c  - Support for Maxim thermocouple chips
   3  *
   4  * Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14  * GNU General Public License for more details.
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/init.h>
  19 #include <linux/mutex.h>
  20 #include <linux/err.h>
  21 #include <linux/spi/spi.h>
  22 #include <linux/iio/iio.h>
  23 #include <linux/iio/trigger.h>
  24 #include <linux/iio/buffer.h>
  25 #include <linux/iio/triggered_buffer.h>
  26 #include <linux/iio/trigger_consumer.h>
  27
  28 #define MAXIM_THERMOCOUPLE_DRV_NAME     "maxim_thermocouple"
  29
  30 enum {
  31         MAX6675,
  32         MAX31855,
  33 };
  34
  35 static const struct iio_chan_spec max6675_channels[] = {
  36         {       /* thermocouple temperature */
  37                 .type = IIO_TEMP,
  38                 .info_mask_separate =
  39                         BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
  40                 .scan_index = 0,
  41                 .scan_type = {
  42                         .sign = 's',
  43                         .realbits = 13,
  44                         .storagebits = 16,
  45                         .shift = 3,
  46                         .endianness = IIO_BE,
  47                 },
  48         },
  49         IIO_CHAN_SOFT_TIMESTAMP(1),
  50 };
  51
  52 static const struct iio_chan_spec max31855_channels[] = {
  53         {       /* thermocouple temperature */
  54                 .type = IIO_TEMP,
  55                 .address = 2,
  56                 .info_mask_separate =
  57                         BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
  58                 .scan_index = 0,
  59                 .scan_type = {
  60                         .sign = 's',
  61                         .realbits = 14,
  62                         .storagebits = 16,
  63                         .shift = 2,
  64                         .endianness = IIO_BE,
  65                 },
  66         },
  67         {       /* cold junction temperature */
  68                 .type = IIO_TEMP,
  69                 .address = 0,
  70                 .channel2 = IIO_MOD_TEMP_AMBIENT,
  71                 .modified = 1,
  72                 .info_mask_separate =
  73                         BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
  74                 .scan_index = 1,
  75                 .scan_type = {
  76                         .sign = 's',
  77                         .realbits = 12,
  78                         .storagebits = 16,
  79                         .shift = 4,
  80                         .endianness = IIO_BE,
  81                 },
  82         },
  83         IIO_CHAN_SOFT_TIMESTAMP(2),
  84 };
  85
  86 static const unsigned long max31855_scan_masks[] = {0x3, 0};
  87
  88 struct maxim_thermocouple_chip {
  89         const struct iio_chan_spec *channels;
  90         const unsigned long *scan_masks;
  91         u8 num_channels;
  92         u8 read_size;
  93
  94         /* bit-check for valid input */
  95         u32 status_bit;
  96 };
  97
  98 static const struct maxim_thermocouple_chip maxim_thermocouple_chips[] = {
  99         [MAX6675] = {
 100                         .channels = max6675_channels,
 101                         .num_channels = ARRAY_SIZE(max6675_channels),
 102                         .read_size = 2,
 103                         .status_bit = BIT(2),
 104                 },
 105         [MAX31855] = {
 106                         .channels = max31855_channels,
 107                         .num_channels = ARRAY_SIZE(max31855_channels),
 108                         .read_size = 4,
 109                         .scan_masks = max31855_scan_masks,
 110                         .status_bit = BIT(16),
 111                 },
 112 };
 113
 114 struct maxim_thermocouple_data {
 115         struct spi_device *spi;
 116         const struct maxim_thermocouple_chip *chip;
 117
 118         u8 buffer[16] ____cacheline_aligned;
 119 };
 120
 121 static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
 122                                    struct iio_chan_spec const *chan, int *val)
 123 {
 124         unsigned int storage_bytes = data->chip->read_size;
 125         unsigned int shift = chan->scan_type.shift + (chan->address * 8);
 126         unsigned int buf;
 127         int ret;
 128
 129         ret = spi_read(data->spi, (void *) &buf, storage_bytes);
 130         if (ret)
 131                 return ret;
 132
 133         switch (storage_bytes) {
 134         case 2:
 135                 *val = be16_to_cpu(buf);
 136                 break;
 137         case 4:
 138                 *val = be32_to_cpu(buf);
 139                 break;
 140         }
 141
 142         /* check to be sure this is a valid reading */
 143         if (*val & data->chip->status_bit)
 144                 return -EINVAL;
 145
 146         *val = sign_extend32(*val >> shift, chan->scan_type.realbits - 1);
 147
 148         return 0;
 149 }
 150
 151 static irqreturn_t maxim_thermocouple_trigger_handler(int irq, void *private)
 152 {
 153         struct iio_poll_func *pf = private;
 154         struct iio_dev *indio_dev = pf->indio_dev;
 155         struct maxim_thermocouple_data *data = iio_priv(indio_dev);
 156         int ret;
 157
 158         ret = spi_read(data->spi, data->buffer, data->chip->read_size);
 159         if (!ret) {
 160                 iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
 161                                                    iio_get_time_ns(indio_dev));
 162         }
 163
 164         iio_trigger_notify_done(indio_dev->trig);
 165
 166         return IRQ_HANDLED;
 167 }
 168
 169 static int maxim_thermocouple_read_raw(struct iio_dev *indio_dev,
 170                                        struct iio_chan_spec const *chan,
 171                                        int *val, int *val2, long mask)
 172 {
 173         struct maxim_thermocouple_data *data = iio_priv(indio_dev);
 174         int ret = -EINVAL;
 175
 176         switch (mask) {
 177         case IIO_CHAN_INFO_RAW:
 178                 ret = iio_device_claim_direct_mode(indio_dev);
 179                 if (ret)
 180                         return ret;
 181
 182                 ret = maxim_thermocouple_read(data, chan, val);
 183                 iio_device_release_direct_mode(indio_dev);
 184
 185                 if (!ret)
 186                         return IIO_VAL_INT;
 187
 188                 break;
 189         case IIO_CHAN_INFO_SCALE:
 190                 switch (chan->channel2) {
 191                 case IIO_MOD_TEMP_AMBIENT:
 192                         *val = 62;
 193                         *val2 = 500000; /* 1000 * 0.0625 */
 194                         ret = IIO_VAL_INT_PLUS_MICRO;
 195                         break;
 196                 default:
 197                         *val = 250; /* 1000 * 0.25 */
 198                         ret = IIO_VAL_INT;
 199                 };
 200                 break;
 201         }
 202
 203         return ret;
 204 }
 205
 206 static const struct iio_info maxim_thermocouple_info = {
 207         .driver_module = THIS_MODULE,
 208         .read_raw = maxim_thermocouple_read_raw,
 209 };
 210
 211 static int maxim_thermocouple_probe(struct spi_device *spi)
 212 {
 213         const struct spi_device_id *id = spi_get_device_id(spi);
 214         struct iio_dev *indio_dev;
 215         struct maxim_thermocouple_data *data;
 216         const struct maxim_thermocouple_chip *chip =
 217                         &maxim_thermocouple_chips[id->driver_data];
 218         int ret;
 219
 220         indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
 221         if (!indio_dev)
 222                 return -ENOMEM;
 223
 224         indio_dev->info = &maxim_thermocouple_info;
 225         indio_dev->name = MAXIM_THERMOCOUPLE_DRV_NAME;
 226         indio_dev->channels = chip->channels;
 227         indio_dev->available_scan_masks = chip->scan_masks;
 228         indio_dev->num_channels = chip->num_channels;
 229         indio_dev->modes = INDIO_DIRECT_MODE;
 230
 231         data = iio_priv(indio_dev);
 232         data->spi = spi;
 233         data->chip = chip;
 234
 235         ret = iio_triggered_buffer_setup(indio_dev, NULL,
 236                                 maxim_thermocouple_trigger_handler, NULL);
 237         if (ret)
 238                 return ret;
 239
 240         ret = iio_device_register(indio_dev);
 241         if (ret)
 242                 goto error_unreg_buffer;
 243
 244         return 0;
 245
 246 error_unreg_buffer:
 247         iio_triggered_buffer_cleanup(indio_dev);
 248
 249         return ret;
 250 }
 251
 252 static int maxim_thermocouple_remove(struct spi_device *spi)
 253 {
 254         struct iio_dev *indio_dev = spi_get_drvdata(spi);
 255
 256         iio_device_unregister(indio_dev);
 257         iio_triggered_buffer_cleanup(indio_dev);
 258
 259         return 0;
 260 }
 261
 262 static const struct spi_device_id maxim_thermocouple_id[] = {
 263         {"max6675", MAX6675},
 264         {"max31855", MAX31855},
 265         {},
 266 };
 267 MODULE_DEVICE_TABLE(spi, maxim_thermocouple_id);
 268
 269 static struct spi_driver maxim_thermocouple_driver = {
 270         .driver = {
 271                 .name   = MAXIM_THERMOCOUPLE_DRV_NAME,
 272         },
 273         .probe          = maxim_thermocouple_probe,
 274         .remove         = maxim_thermocouple_remove,
 275         .id_table       = maxim_thermocouple_id,
 276 };
 277 module_spi_driver(maxim_thermocouple_driver);
 278
 279 MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
 280 MODULE_DESCRIPTION("Maxim thermocouple sensors");
 281 MODULE_LICENSE("GPL");