hwmon: add TI ads7871 a/d converter driver

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Paul Thomas <pthomas8589@gmail.com>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 253 insertions, 0 deletions

diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c
new file mode 100644
index 000000000000..b300a2048af1
--- /dev/null
+++ b/drivers/hwmon/ads7871.c
@@ -0,0 +1,253 @@
+/*
+ *  ads7871 - driver for TI ADS7871 A/D converter
+ *
+ *  Copyright (c) 2010 Paul Thomas <pthomas8589@gmail.com>
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ *  GNU General Public License for more details.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2 or
+ *  later as publishhed by the Free Software Foundation.
+ *
+ *      You need to have something like this in struct spi_board_info
+ *      {
+ *              .modalias       = "ads7871",
+ *              .max_speed_hz   = 2*1000*1000,
+ *              .chip_select    = 0,
+ *              .bus_num        = 1,
+ *      },
+ */
+
+/*From figure 18 in the datasheet*/
+/*Register addresses*/
+#define REG_LS_BYTE     0 /*A/D Output Data, LS Byte*/
+#define REG_MS_BYTE     1 /*A/D Output Data, MS Byte*/
+#define REG_PGA_VALID   2 /*PGA Valid Register*/
+#define REG_AD_CONTROL  3 /*A/D Control Register*/
+#define REG_GAIN_MUX    4 /*Gain/Mux Register*/
+#define REG_IO_STATE    5 /*Digital I/O State Register*/
+#define REG_IO_CONTROL  6 /*Digital I/O Control Register*/
+#define REG_OSC_CONTROL 7 /*Rev/Oscillator Control Register*/
+#define REG_SER_CONTROL 24 /*Serial Interface Control Register*/
+#define REG_ID          31 /*ID Register*/
+
+/*From figure 17 in the datasheet
+* These bits get ORed with the address to form
+* the instruction byte */
+/*Instruction Bit masks*/
+#define INST_MODE_bm    (1<<7)
+#define INST_READ_bm    (1<<6)
+#define INST_16BIT_bm   (1<<5)
+
+/*From figure 18 in the datasheet*/
+/*bit masks for Rev/Oscillator Control Register*/
+#define MUX_CNV_bv      7
+#define MUX_CNV_bm      (1<<MUX_CNV_bv)
+#define MUX_M3_bm       (1<<3) /*M3 selects single ended*/
+#define MUX_G_bv        4 /*allows for reg = (gain << MUX_G_bv) | ...*/
+
+/*From figure 18 in the datasheet*/
+/*bit masks for Rev/Oscillator Control Register*/
+#define OSC_OSCR_bm     (1<<5)
+#define OSC_OSCE_bm     (1<<4)
+#define OSC_REFE_bm     (1<<3)
+#define OSC_BUFE_bm     (1<<2)
+#define OSC_R2V_bm      (1<<1)
+#define OSC_RBG_bm      (1<<0)
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/spi/spi.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+
+#define DEVICE_NAME     "ads7871"
+
+struct ads7871_data {
+        struct device   *hwmon_dev;
+        struct mutex    update_lock;
+};
+
+static int ads7871_read_reg8(struct spi_device *spi, int reg)
+{
+        int ret;
+        reg = reg | INST_READ_bm;
+        ret = spi_w8r8(spi, reg);
+        return ret;
+}
+
+static int ads7871_read_reg16(struct spi_device *spi, int reg)
+{
+        int ret;
+        reg = reg | INST_READ_bm | INST_16BIT_bm;
+        ret = spi_w8r16(spi, reg);
+        return ret;
+}
+
+static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val)
+{
+        u8 tmp[2] = {reg, val};
+        return spi_write(spi, tmp, sizeof(tmp));
+}
+
+static ssize_t show_voltage(struct device *dev,
+                struct device_attribute *da, char *buf)
+{
+        struct spi_device *spi = to_spi_device(dev);
+        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+        int ret, val, i = 0;
+        uint8_t channel, mux_cnv;
+
+        channel = attr->index;
+        /*TODO: add support for conversions
+         *other than single ended with a gain of 1*/
+        /*MUX_M3_bm forces single ended*/
+        /*This is also where the gain of the PGA would be set*/
+        ads7871_write_reg8(spi, REG_GAIN_MUX,
+                (MUX_CNV_bm | MUX_M3_bm | channel));
+
+        ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
+        mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
+        /*on 400MHz arm9 platform the conversion
+         *is already done when we do this test*/
+        while ((i < 2) && mux_cnv) {
+                i++;
+                ret = ads7871_read_reg8(spi, REG_GAIN_MUX);
+                mux_cnv = ((ret & MUX_CNV_bm)>>MUX_CNV_bv);
+                msleep_interruptible(1);
+        }
+
+        if (mux_cnv == 0) {
+                val = ads7871_read_reg16(spi, REG_LS_BYTE);
+                /*result in volts*10000 = (val/8192)*2.5*10000*/
+                val = ((val>>2) * 25000) / 8192;
+                return sprintf(buf, "%d\n", val);
+        } else {
+                return -1;
+        }
+}
+
+static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, show_voltage, NULL, 0);
+static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, show_voltage, NULL, 1);
+static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, show_voltage, NULL, 2);
+static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, show_voltage, NULL, 3);
+static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, show_voltage, NULL, 4);
+static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, show_voltage, NULL, 5);
+static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, show_voltage, NULL, 6);
+static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, show_voltage, NULL, 7);
+
+static struct attribute *ads7871_attributes[] = {
+        &sensor_dev_attr_in0_input.dev_attr.attr,
+        &sensor_dev_attr_in1_input.dev_attr.attr,
+        &sensor_dev_attr_in2_input.dev_attr.attr,
+        &sensor_dev_attr_in3_input.dev_attr.attr,
+        &sensor_dev_attr_in4_input.dev_attr.attr,
+        &sensor_dev_attr_in5_input.dev_attr.attr,
+        &sensor_dev_attr_in6_input.dev_attr.attr,
+        &sensor_dev_attr_in7_input.dev_attr.attr,
+        NULL
+};
+
+static const struct attribute_group ads7871_group = {
+        .attrs = ads7871_attributes,
+};
+
+static int __devinit ads7871_probe(struct spi_device *spi)
+{
+        int status, ret, err = 0;
+        uint8_t val;
+        struct ads7871_data *pdata;
+
+        dev_dbg(&spi->dev, "probe\n");
+
+        pdata = kzalloc(sizeof(struct ads7871_data), GFP_KERNEL);
+        if (!pdata) {
+                err = -ENOMEM;
+                goto exit;
+        }
+
+        status = sysfs_create_group(&spi->dev.kobj, &ads7871_group);
+        if (status < 0)
+                goto error_free;
+
+        pdata->hwmon_dev = hwmon_device_register(&spi->dev);
+        if (IS_ERR(pdata->hwmon_dev)) {
+                err = PTR_ERR(pdata->hwmon_dev);
+                goto error_remove;
+        }
+
+        spi_set_drvdata(spi, pdata);
+
+        /* Configure the SPI bus */
+        spi->mode = (SPI_MODE_0);
+        spi->bits_per_word = 8;
+        spi_setup(spi);
+
+        ads7871_write_reg8(spi, REG_SER_CONTROL, 0);
+        ads7871_write_reg8(spi, REG_AD_CONTROL, 0);
+
+        val = (OSC_OSCR_bm | OSC_OSCE_bm | OSC_REFE_bm | OSC_BUFE_bm);
+        ads7871_write_reg8(spi, REG_OSC_CONTROL, val);
+        ret = ads7871_read_reg8(spi, REG_OSC_CONTROL);
+
+        dev_dbg(&spi->dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret);
+        /*because there is no other error checking on an SPI bus
+        we need to make sure we really have a chip*/
+        if (val != ret) {
+                err = -ENODEV;
+                goto error_remove;
+        }
+
+        return 0;
+
+error_remove:
+        sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
+error_free:
+        kfree(pdata);
+exit:
+        return err;
+}
+
+static int __devexit ads7871_remove(struct spi_device *spi)
+{
+        struct ads7871_data *pdata = spi_get_drvdata(spi);
+
+        hwmon_device_unregister(pdata->hwmon_dev);
+        sysfs_remove_group(&spi->dev.kobj, &ads7871_group);
+        kfree(pdata);
+        return 0;
+}
+
+static struct spi_driver ads7871_driver = {
+        .driver = {
+                .name = DEVICE_NAME,
+                .bus = &spi_bus_type,
+                .owner = THIS_MODULE,
+        },
+
+        .probe = ads7871_probe,
+        .remove = __devexit_p(ads7871_remove),
+};
+
+static int __init ads7871_init(void)
+{
+        return spi_register_driver(&ads7871_driver);
+}
+
+static void __exit ads7871_exit(void)
+{
+        spi_unregister_driver(&ads7871_driver);
+}
+
+module_init(ads7871_init);
+module_exit(ads7871_exit);
+
+MODULE_AUTHOR("Paul Thomas <pthomas8589@gmail.com>");
+MODULE_DESCRIPTION("TI ADS7871 A/D driver");
+MODULE_LICENSE("GPL");