7a18afe809
On ads7828 the internal reference defaults to off upon power up. When using internal reference, it needs to be turned on and the voltage needs to settle before normal conversion cycle can be started. Hence perform a dummy read in the probe to enable the internal reference allowing the voltage to settle before performing a normal read. Without this fix, the first read from the ADC when using internal reference always returns incorrect data. Signed-off-by: Akshay Bhat <akshay.bhat@timesys.com> Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Guenter Roeck <linux@roeck-us.net>
193 lines
6 KiB
C
193 lines
6 KiB
C
/*
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* ads7828.c - driver for TI ADS7828 8-channel A/D converter and compatibles
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* (C) 2007 EADS Astrium
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*
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* This driver is based on the lm75 and other lm_sensors/hwmon drivers
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*
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* Written by Steve Hardy <shardy@redhat.com>
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*
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* ADS7830 support, by Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>
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*
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* For further information, see the Documentation/hwmon/ads7828 file.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <linux/err.h>
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#include <linux/hwmon.h>
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#include <linux/hwmon-sysfs.h>
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#include <linux/i2c.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/platform_data/ads7828.h>
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#include <linux/regmap.h>
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#include <linux/slab.h>
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/* The ADS7828 registers */
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#define ADS7828_CMD_SD_SE 0x80 /* Single ended inputs */
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#define ADS7828_CMD_PD1 0x04 /* Internal vref OFF && A/D ON */
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#define ADS7828_CMD_PD3 0x0C /* Internal vref ON && A/D ON */
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#define ADS7828_INT_VREF_MV 2500 /* Internal vref is 2.5V, 2500mV */
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#define ADS7828_EXT_VREF_MV_MIN 50 /* External vref min value 0.05V */
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#define ADS7828_EXT_VREF_MV_MAX 5250 /* External vref max value 5.25V */
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/* List of supported devices */
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enum ads7828_chips { ads7828, ads7830 };
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/* Client specific data */
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struct ads7828_data {
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struct regmap *regmap;
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u8 cmd_byte; /* Command byte without channel bits */
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unsigned int lsb_resol; /* Resolution of the ADC sample LSB */
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};
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/* Command byte C2,C1,C0 - see datasheet */
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static inline u8 ads7828_cmd_byte(u8 cmd, int ch)
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{
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return cmd | (((ch >> 1) | (ch & 0x01) << 2) << 4);
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}
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/* sysfs callback function */
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static ssize_t ads7828_show_in(struct device *dev, struct device_attribute *da,
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char *buf)
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{
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struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
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struct ads7828_data *data = dev_get_drvdata(dev);
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u8 cmd = ads7828_cmd_byte(data->cmd_byte, attr->index);
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unsigned int regval;
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int err;
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err = regmap_read(data->regmap, cmd, ®val);
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if (err < 0)
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return err;
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return sprintf(buf, "%d\n",
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DIV_ROUND_CLOSEST(regval * data->lsb_resol, 1000));
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}
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static SENSOR_DEVICE_ATTR(in0_input, S_IRUGO, ads7828_show_in, NULL, 0);
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static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ads7828_show_in, NULL, 1);
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static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ads7828_show_in, NULL, 2);
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static SENSOR_DEVICE_ATTR(in3_input, S_IRUGO, ads7828_show_in, NULL, 3);
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static SENSOR_DEVICE_ATTR(in4_input, S_IRUGO, ads7828_show_in, NULL, 4);
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static SENSOR_DEVICE_ATTR(in5_input, S_IRUGO, ads7828_show_in, NULL, 5);
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static SENSOR_DEVICE_ATTR(in6_input, S_IRUGO, ads7828_show_in, NULL, 6);
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static SENSOR_DEVICE_ATTR(in7_input, S_IRUGO, ads7828_show_in, NULL, 7);
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static struct attribute *ads7828_attrs[] = {
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&sensor_dev_attr_in0_input.dev_attr.attr,
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&sensor_dev_attr_in1_input.dev_attr.attr,
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&sensor_dev_attr_in2_input.dev_attr.attr,
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&sensor_dev_attr_in3_input.dev_attr.attr,
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&sensor_dev_attr_in4_input.dev_attr.attr,
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&sensor_dev_attr_in5_input.dev_attr.attr,
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&sensor_dev_attr_in6_input.dev_attr.attr,
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&sensor_dev_attr_in7_input.dev_attr.attr,
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NULL
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};
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ATTRIBUTE_GROUPS(ads7828);
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static const struct regmap_config ads2828_regmap_config = {
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.reg_bits = 8,
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.val_bits = 16,
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};
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static const struct regmap_config ads2830_regmap_config = {
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.reg_bits = 8,
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.val_bits = 8,
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};
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static int ads7828_probe(struct i2c_client *client,
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const struct i2c_device_id *id)
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{
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struct device *dev = &client->dev;
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struct ads7828_platform_data *pdata = dev_get_platdata(dev);
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struct ads7828_data *data;
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struct device *hwmon_dev;
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unsigned int vref_mv = ADS7828_INT_VREF_MV;
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bool diff_input = false;
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bool ext_vref = false;
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unsigned int regval;
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data = devm_kzalloc(dev, sizeof(struct ads7828_data), GFP_KERNEL);
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if (!data)
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return -ENOMEM;
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if (pdata) {
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diff_input = pdata->diff_input;
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ext_vref = pdata->ext_vref;
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if (ext_vref && pdata->vref_mv)
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vref_mv = pdata->vref_mv;
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}
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/* Bound Vref with min/max values */
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vref_mv = clamp_val(vref_mv, ADS7828_EXT_VREF_MV_MIN,
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ADS7828_EXT_VREF_MV_MAX);
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/* ADS7828 uses 12-bit samples, while ADS7830 is 8-bit */
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if (id->driver_data == ads7828) {
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data->lsb_resol = DIV_ROUND_CLOSEST(vref_mv * 1000, 4096);
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data->regmap = devm_regmap_init_i2c(client,
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&ads2828_regmap_config);
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} else {
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data->lsb_resol = DIV_ROUND_CLOSEST(vref_mv * 1000, 256);
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data->regmap = devm_regmap_init_i2c(client,
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&ads2830_regmap_config);
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}
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if (IS_ERR(data->regmap))
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return PTR_ERR(data->regmap);
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data->cmd_byte = ext_vref ? ADS7828_CMD_PD1 : ADS7828_CMD_PD3;
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if (!diff_input)
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data->cmd_byte |= ADS7828_CMD_SD_SE;
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/*
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* Datasheet specifies internal reference voltage is disabled by
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* default. The internal reference voltage needs to be enabled and
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* voltage needs to settle before getting valid ADC data. So perform a
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* dummy read to enable the internal reference voltage.
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*/
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if (!ext_vref)
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regmap_read(data->regmap, data->cmd_byte, ®val);
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hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
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data,
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ads7828_groups);
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return PTR_ERR_OR_ZERO(hwmon_dev);
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}
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static const struct i2c_device_id ads7828_device_ids[] = {
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{ "ads7828", ads7828 },
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{ "ads7830", ads7830 },
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{ }
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};
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MODULE_DEVICE_TABLE(i2c, ads7828_device_ids);
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static struct i2c_driver ads7828_driver = {
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.driver = {
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.name = "ads7828",
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},
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.id_table = ads7828_device_ids,
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.probe = ads7828_probe,
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};
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module_i2c_driver(ads7828_driver);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Steve Hardy <shardy@redhat.com>");
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MODULE_DESCRIPTION("Driver for TI ADS7828 A/D converter and compatibles");
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