[PATCH v4 4/4] iio: humidity: si7020: added No Hold read mode

Nicola Corna
2015-10-28T06:58:26Z

The Si7013/20/21 modules support 2 read modes:
* Hold mode (blocking), where the device stretches the clock until the end
of the measurement
* No Hold mode (non-blocking), where the device replies NACK for every I2C
call during the measurement
Here the No Hold mode is implemented, selectable with the blocking_io
variable within si7020_platform_data. The default mode is Hold, unless the
adapter does not support clock stretching, in which case the No Hold mode
is used.

Signed-off-by: Nicola Corna <nicola@corna.info>
---
This patch depends on patch "[PATCH v4 1/2] iio: humidity: si7020: replaced
bitmask on humidity values with range check"
drivers/iio/humidity/si7020.c | 78 ++++++++++++++++++++++++++++++++----
include/linux/platform_data/si7020.h | 21 ++++++++++
2 files changed, 92 insertions(+), 7 deletions(-)
create mode 100644 include/linux/platform_data/si7020.h

diff --git a/drivers/iio/humidity/si7020.c b/drivers/iio/humidity/si7020.c
index 12128d1..c728681 100644
--- a/drivers/iio/humidity/si7020.c
+++ b/drivers/iio/humidity/si7020.c
@@ -2,6 +2,7 @@
* si7020.c - Silicon Labs Si7013/20/21 Relative Humidity and Temp Sensors
* Copyright (c) 2013,2014 Uplogix, Inc.
* David Barksdale <dbarksdale@uplogix.com>
+ * Copyright (c) 2015 Nicola Corna <nicola@corna.info>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms and conditions of the GNU General Public License,
@@ -30,33 +31,79 @@
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/sysfs.h>
+#include <linux/jiffies.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
+#include <linux/platform_data/si7020.h>

/* Measure Relative Humidity, Hold Master Mode */
#define SI7020CMD_RH_HOLD 0xE5
+/* Measure Relative Humidity, No Hold Master Mode */
+#define SI7020CMD_RH_NO_HOLD 0xF5
/* Measure Temperature, Hold Master Mode */
#define SI7020CMD_TEMP_HOLD 0xE3
+/* Measure Temperature, No Hold Master Mode */
+#define SI7020CMD_TEMP_NO_HOLD 0xF3
/* Software Reset */
#define SI7020CMD_RESET 0xFE
+/* Relative humidity measurement timeout (us) */
+#define SI7020_RH_TIMEOUT 22800
+/* Temperature measurement timeout (us) */
+#define SI7020_TEMP_TIMEOUT 10800
+/* Minimum delay between retries (No Hold Mode) in us */
+#define SI7020_NOHOLD_SLEEP_MIN 2000
+/* Maximum delay between retries (No Hold Mode) in us */
+#define SI7020_NOHOLD_SLEEP_MAX 6000

static int si7020_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan, int *val,
int *val2, long mask)
{
struct i2c_client **client = iio_priv(indio_dev);
+ struct si7020_platform_data *pdata;
int ret;
+ bool holdmode;
+ unsigned char buf[2];
+ unsigned long start;

switch (mask) {
case IIO_CHAN_INFO_RAW:
- ret = i2c_smbus_read_word_data(*client,
- chan->type == IIO_TEMP ?
- SI7020CMD_TEMP_HOLD :
- SI7020CMD_RH_HOLD);
- if (ret < 0)
- return ret;
- *val = ret >> 2;
+ pdata = dev_get_platdata(&(*client)->dev);
+ if (pdata)
+ holdmode = pdata->blocking_io;
+ else
+ holdmode = !((*client)->adapter->quirks &&
+ (*client)->adapter->quirks->flags &
+ I2C_AQ_NO_CLK_STRETCH);
+ if (holdmode) {
+ ret = i2c_smbus_read_word_data(*client,
+ chan->type == IIO_TEMP ?
+ SI7020CMD_TEMP_HOLD :
+ SI7020CMD_RH_HOLD);
+ if (ret < 0)
+ return ret;
+ *val = ret >> 2;
+ } else {
+ ret = i2c_smbus_write_byte(*client,
+ chan->type == IIO_TEMP ?
+ SI7020CMD_TEMP_NO_HOLD :
+ SI7020CMD_RH_NO_HOLD);
+ if (ret < 0)
+ return ret;
+ start = jiffies;
+ while ((ret = i2c_master_recv(*client, buf, 2)) < 0) {
+ if (time_after(jiffies, start +
+ usecs_to_jiffies(
+ chan->type == IIO_TEMP ?
+ SI7020_TEMP_TIMEOUT :
+ SI7020_RH_TIMEOUT)))
+ return ret;
+ usleep_range(SI7020_NOHOLD_SLEEP_MIN,
+ SI7020_NOHOLD_SLEEP_MAX);
+ }
+ *val = ((buf[0] << 8) | buf[1]) >> 2;
+ }
/*
* Humidity values can slightly exceed the 0-100%RH
* range and should be corrected by software
@@ -116,6 +163,7 @@ static int si7020_probe(struct i2c_client *client,
{
struct iio_dev *indio_dev;
struct i2c_client **data;
+ struct si7020_platform_data *pdata;
int ret;

if (!i2c_check_functionality(client->adapter,
@@ -123,6 +171,22 @@ static int si7020_probe(struct i2c_client *client,
I2C_FUNC_SMBUS_READ_WORD_DATA))
return -ENODEV;

+ pdata = dev_get_platdata(&client->dev);
+ if (pdata) {
+ if (pdata->blocking_io) {
+ if (client->adapter->quirks &&
+ client->adapter->quirks->flags &
+ I2C_AQ_NO_CLK_STRETCH)
+ return -ENODEV;
+ } else if (!i2c_check_functionality(client->adapter,
+ I2C_FUNC_I2C))
+ return -ENODEV;
+ } else
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C) &&
+ client->adapter->quirks &&
+ client->adapter->quirks->flags & I2C_AQ_NO_CLK_STRETCH)
+ return -ENODEV;
+
/* Reset device, loads default settings. */
ret = i2c_smbus_write_byte(client, SI7020CMD_RESET);
if (ret < 0)
diff --git a/include/linux/platform_data/si7020.h b/include/linux/platform_data/si7020.h
new file mode 100644
index 0000000..8bb5848
--- /dev/null
+++ b/include/linux/platform_data/si7020.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2015 Nicola Corna <nicola@corna.info>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * 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.
+ *
+ */
+
+#ifndef __SI7020_H_
+#define __SI7020_H_
+
+struct si7020_platform_data {
+ bool blocking_io;
+};
+#endif /* __SI7020_H_ */
--
2.6.1