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 41 42 #define DRVNAME "lm70" 43 44 #define LM70_CHIP_LM70 0 /* original NS LM70 */ 45 #define LM70_CHIP_TMP121 1 /* TI TMP121/TMP123 */ 46 #define LM70_CHIP_LM71 2 /* NS LM71 */ 47 #define LM70_CHIP_LM74 3 /* NS LM74 */ 48 49 struct lm70 { 50 struct spi_device *spi; 51 struct mutex lock; 52 unsigned int chip; 53 }; 54 55 /* sysfs hook function */ 56 static ssize_t lm70_sense_temp(struct device *dev, 57 struct device_attribute *attr, char *buf) 58 { 59 struct lm70 *p_lm70 = dev_get_drvdata(dev); 60 struct spi_device *spi = p_lm70->spi; 61 int status, val = 0; 62 u8 rxbuf[2]; 63 s16 raw = 0; 64 65 if (mutex_lock_interruptible(&p_lm70->lock)) 66 return -ERESTARTSYS; 67 68 /* 69 * spi_read() requires a DMA-safe buffer; so we use 70 * spi_write_then_read(), transmitting 0 bytes. 71 */ 72 status = spi_write_then_read(spi, NULL, 0, &rxbuf[0], 2); 73 if (status < 0) { 74 pr_warn("spi_write_then_read failed with status %d\n", status); 75 goto out; 76 } 77 raw = (rxbuf[0] << 8) + rxbuf[1]; 78 dev_dbg(dev, "rxbuf[0] : 0x%02x rxbuf[1] : 0x%02x raw=0x%04x\n", 79 rxbuf[0], rxbuf[1], raw); 80 81 /* 82 * LM70: 83 * The "raw" temperature read into rxbuf[] is a 16-bit signed 2's 84 * complement value. Only the MSB 11 bits (1 sign + 10 temperature 85 * bits) are meaningful; the LSB 5 bits are to be discarded. 86 * See the datasheet. 87 * 88 * Further, each bit represents 0.25 degrees Celsius; so, multiply 89 * by 0.25. Also multiply by 1000 to represent in millidegrees 90 * Celsius. 91 * So it's equivalent to multiplying by 0.25 * 1000 = 250. 92 * 93 * LM74 and TMP121/TMP123: 94 * 13 bits of 2's complement data, discard LSB 3 bits, 95 * resolution 0.0625 degrees celsius. 96 * 97 * LM71: 98 * 14 bits of 2's complement data, discard LSB 2 bits, 99 * resolution 0.0312 degrees celsius. 100 */ 101 switch (p_lm70->chip) { 102 case LM70_CHIP_LM70: 103 val = ((int)raw / 32) * 250; 104 break; 105 106 case LM70_CHIP_TMP121: 107 case LM70_CHIP_LM74: 108 val = ((int)raw / 8) * 625 / 10; 109 break; 110 111 case LM70_CHIP_LM71: 112 val = ((int)raw / 4) * 3125 / 100; 113 break; 114 } 115 116 status = sprintf(buf, "%d\n", val); /* millidegrees Celsius */ 117 out: 118 mutex_unlock(&p_lm70->lock); 119 return status; 120 } 121 122 static DEVICE_ATTR(temp1_input, S_IRUGO, lm70_sense_temp, NULL); 123 124 static struct attribute *lm70_attrs[] = { 125 &dev_attr_temp1_input.attr, 126 NULL 127 }; 128 129 ATTRIBUTE_GROUPS(lm70); 130 131 /*----------------------------------------------------------------------*/ 132 133 static int lm70_probe(struct spi_device *spi) 134 { 135 int chip = spi_get_device_id(spi)->driver_data; 136 struct device *hwmon_dev; 137 struct lm70 *p_lm70; 138 139 /* signaling is SPI_MODE_0 */ 140 if (spi->mode & (SPI_CPOL | SPI_CPHA)) 141 return -EINVAL; 142 143 /* NOTE: we assume 8-bit words, and convert to 16 bits manually */ 144 145 p_lm70 = devm_kzalloc(&spi->dev, sizeof(*p_lm70), GFP_KERNEL); 146 if (!p_lm70) 147 return -ENOMEM; 148 149 mutex_init(&p_lm70->lock); 150 p_lm70->chip = chip; 151 p_lm70->spi = spi; 152 153 hwmon_dev = devm_hwmon_device_register_with_groups(&spi->dev, 154 spi->modalias, 155 p_lm70, lm70_groups); 156 return PTR_ERR_OR_ZERO(hwmon_dev); 157 } 158 159 static const struct spi_device_id lm70_ids[] = { 160 { "lm70", LM70_CHIP_LM70 }, 161 { "tmp121", LM70_CHIP_TMP121 }, 162 { "lm71", LM70_CHIP_LM71 }, 163 { "lm74", LM70_CHIP_LM74 }, 164 { }, 165 }; 166 MODULE_DEVICE_TABLE(spi, lm70_ids); 167 168 static struct spi_driver lm70_driver = { 169 .driver = { 170 .name = "lm70", 171 .owner = THIS_MODULE, 172 }, 173 .id_table = lm70_ids, 174 .probe = lm70_probe, 175 }; 176 177 module_spi_driver(lm70_driver); 178 179 MODULE_AUTHOR("Kaiwan N Billimoria"); 180 MODULE_DESCRIPTION("NS LM70 and compatibles Linux driver"); 181 MODULE_LICENSE("GPL"); 182