drivers/hwmon/lm70.c

   1 /*
   2  * lm70.c
   3  *
   4  * The LM70 is a temperature sensor chip from National Semiconductor (NS).
   5  * Copyright (C) 2006 Kaiwan N Billimoria <kaiwan@designergraphix.com>
   6  *
   7  * The LM70 communicates with a host processor via an SPI/Microwire Bus
   8  * interface. The complete datasheet is available at National's website
   9  * here:
  10  * http://www.national.com/pf/LM/LM70.html
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License
  23  * along with this program; if not, write to the Free Software
  24  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  25  */
  26
  27 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  28
  29 #include <linux/init.h>
  30 #include <linux/module.h>
  31 #include <linux/kernel.h>
  32 #include <linux/device.h>
  33 #include <linux/err.h>
  34 #include <linux/sysfs.h>
  35 #include <linux/hwmon.h>
  36 #include <linux/mutex.h>
  37 #include <linux/mod_devicetable.h>
  38 #include <linux/spi/spi.h>
  39 #include <linux/slab.h>
  40 #include <linux/of_device.h>
  41
  42
  43 #define DRVNAME         "lm70"
  44
  45 #define LM70_CHIP_LM70          0       /* original NS LM70 */
  46 #define LM70_CHIP_TMP121        1       /* TI TMP121/TMP123 */
  47 #define LM70_CHIP_LM71          2       /* NS LM71 */
  48 #define LM70_CHIP_LM74          3       /* NS LM74 */
  49
  50 struct lm70 {
  51         struct spi_device *spi;
  52         struct mutex lock;
  53         unsigned int chip;
  54 };
  55
  56 /* sysfs hook function */
  57 static ssize_t lm70_sense_temp(struct device *dev,
  58                 struct device_attribute *attr, char *buf)
  59 {
  60         struct lm70 *p_lm70 = dev_get_drvdata(dev);
  61         struct spi_device *spi = p_lm70->spi;
  62         int status, val = 0;
  63         u8 rxbuf[2];
  64         s16 raw = 0;
  65
  66         if (mutex_lock_interruptible(&p_lm70->lock))
  67                 return -ERESTARTSYS;
  68
  69         /*
  70          * spi_read() requires a DMA-safe buffer; so we use
  71          * spi_write_then_read(), transmitting 0 bytes.
  72          */
  73         status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2);
  74         if (status < 0) {
  75                 pr_warn("spi_write_then_read failed with status %d\n", status);
  76                 goto out;
  77         }
  78         raw = (rxbuf[0] << 8) + rxbuf[1];
  79         dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n",
  80                 rxbuf[0], rxbuf[1], raw);
  81
  82         /*
  83          * LM70:
  84          * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's
  85          * complement value. Only the MSB 11 bits (1 sign + 10 temperature
  86          * bits) are meaningful; the LSB 5 bits are to be discarded.
  87          * See the datasheet.
  88          *
  89          * Further, each bit represents 0.25 degrees Celsius; so, multiply
  90          * by 0.25. Also multiply by 1000 to represent in millidegrees
  91          * Celsius.
  92          * So it's equivalent to multiplying by 0.25 * 1000 = 250.
  93          *
  94          * LM74 and TMP121/TMP123:
  95          * 13 bits of 2's complement data, discard LSB 3 bits,
  96          * resolution 0.0625 degrees celsius.
  97          *
  98          * LM71:
  99          * 14 bits of 2's complement data, discard LSB 2 bits,
 100          * resolution 0.0312 degrees celsius.
 101          */
 102         switch (p_lm70->chip) {
 103         case LM70_CHIP_LM70:
 104                 val = ((int)raw / 32) * 250;
 105                 break;
 106
 107         case LM70_CHIP_TMP121:
 108         case LM70_CHIP_LM74:
 109                 val = ((int)raw / 8) * 625 / 10;
 110                 break;
 111
 112         case LM70_CHIP_LM71:
 113                 val = ((int)raw / 4) * 3125 / 100;
 114                 break;
 115         }
 116
 117         status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */
 118 out:
 119         mutex_unlock(&p_lm70->lock);
 120         return status;
 121 }
 122
 123 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL);
 124
 125 static struct attribute *lm70_attrs[] = {
 126         &dev_attr_temp1_input.attr,
 127         NULL
 128 };
 129
 130 ATTRIBUTE_GROUPS(lm70);
 131
 132 /*----------------------------------------------------------------------*/
 133
 134 #ifdef CONFIG_OF
 135 static const struct of_device_id lm70_of_ids[] = {
 136         {
 137                 .compatible = "ti,lm70",
 138                 .data = (void *) LM70_CHIP_LM70,
 139         },
 140         {
 141                 .compatible = "ti,tmp121",
 142                 .data = (void *) LM70_CHIP_TMP121,
 143         },
 144         {
 145                 .compatible = "ti,lm71",
 146                 .data = (void *) LM70_CHIP_LM71,
 147         },
 148         {
 149                 .compatible = "ti,lm74",
 150                 .data = (void *) LM70_CHIP_LM74,
 151         },
 152         {},
 153 };
 154 MODULE_DEVICE_TABLE(of, lm70_of_ids);
 155 #endif
 156
 157 static int lm70_probe(struct spi_device *spi)
 158 {
 159         const struct of_device_id *match;
 160         struct device *hwmon_dev;
 161         struct lm70 *p_lm70;
 162         int chip;
 163
 164         match = of_match_device(lm70_of_ids, &spi->dev);
 165         if (match)
 166                 chip = (int)(uintptr_t)match->data;
 167         else
 168                 chip = spi_get_device_id(spi)->driver_data;
 169
 170         /* signaling is SPI_MODE_0 */
 171         if (spi->mode & (SPI_CPOL | SPI_CPHA))
 172                 return -EINVAL;
 173
 174         /* NOTE:  we assume 8-bit words, and convert to 16 bits manually */
 175
 176         p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL);
 177         if (!p_lm70)
 178                 return -ENOMEM;
 179
 180         mutex_init(&p_lm70->lock);
 181         p_lm70->chip = chip;
 182         p_lm70->spi = spi;
 183
 184         hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev,
 185                                                            spi->modalias,
 186                                                            p_lm70, lm70_groups);
 187         return PTR_ERR_OR_ZERO(hwmon_dev);
 188 }
 189
 190 static const struct spi_device_id lm70_ids[] = {
 191         { "lm70",   LM70_CHIP_LM70 },
 192         { "tmp121", LM70_CHIP_TMP121 },
 193         { "lm71",   LM70_CHIP_LM71 },
 194         { "lm74",   LM70_CHIP_LM74 },
 195         { },
 196 };
 197 MODULE_DEVICE_TABLE(spi, lm70_ids);
 198
 199 static struct spi_driver lm70_driver = {
 200         .driver = {
 201                 .name   = "lm70",
 202                 .of_match_table = of_match_ptr(lm70_of_ids),
 203         },
 204         .id_table = lm70_ids,
 205         .probe  = lm70_probe,
 206 };
 207
 208 module_spi_driver(lm70_driver);
 209
 210 MODULE_AUTHOR("Kaiwan N Billimoria");
 211 MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver");
 212 MODULE_LICENSE("GPL");