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linux/drivers/i2c/chips/tsl2550.c
Jean Delvare ac7809414f i2c/tsl2550: Use combined SMBus transactions 
Make the I/O faster, mainly by using combined SMBus transactions when
possible. While the TSL2550 datasheet doesn't say the device supports
them, they seem to work just fine in practice, and a combined
transaction is faster than two simple transactions in many cases and
always more reliable.

A side effect is to suppress the delays between SMBus writes and
reads. The datasheet doesn't say they are needed and things work just
fine for me without them.

I also couldn't see any reason for the delay between reading the two
channels. Nor for the loop to get a reading in the first place. The
400 ms delay between samples only matters at chip power-up, after that
the chip always hold the previously sampled value so we never get to
wait.

All these changes make reading the lux value much faster and cheaper.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Michele De Candia <michele.decandia@valueteam.com>
Cc: Rodolfo Giometti <giometti@linux.it>
2009-09-18 22:45:44 +02:00

471 lines
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/*
* tsl2550.c - Linux kernel modules for ambient light sensor
*
* Copyright (C) 2007 Rodolfo Giometti <giometti@linux.it>
* Copyright (C) 2007 Eurotech S.p.A. <info@eurotech.it>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* 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.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
#define TSL2550_DRV_NAME "tsl2550"
#define DRIVER_VERSION "1.2"
/*
* Defines
*/
#define TSL2550_POWER_DOWN 0x00
#define TSL2550_POWER_UP 0x03
#define TSL2550_STANDARD_RANGE 0x18
#define TSL2550_EXTENDED_RANGE 0x1d
#define TSL2550_READ_ADC0 0x43
#define TSL2550_READ_ADC1 0x83
/*
* Structs
*/
struct tsl2550_data {
struct i2c_client *client;
struct mutex update_lock;
unsigned int power_state : 1;
unsigned int operating_mode : 1;
};
/*
* Global data
*/
static const u8 TSL2550_MODE_RANGE[2] = {
TSL2550_STANDARD_RANGE, TSL2550_EXTENDED_RANGE,
};
/*
* Management functions
*/
static int tsl2550_set_operating_mode(struct i2c_client *client, int mode)
{
struct tsl2550_data *data = i2c_get_clientdata(client);
int ret = i2c_smbus_write_byte(client, TSL2550_MODE_RANGE[mode]);
data->operating_mode = mode;
return ret;
}
static int tsl2550_set_power_state(struct i2c_client *client, int state)
{
struct tsl2550_data *data = i2c_get_clientdata(client);
int ret;
if (state == 0)
ret = i2c_smbus_write_byte(client, TSL2550_POWER_DOWN);
else {
ret = i2c_smbus_write_byte(client, TSL2550_POWER_UP);
/* On power up we should reset operating mode also... */
tsl2550_set_operating_mode(client, data->operating_mode);
}
data->power_state = state;
return ret;
}
static int tsl2550_get_adc_value(struct i2c_client *client, u8 cmd)
{
int ret;
ret = i2c_smbus_read_byte_data(client, cmd);
if (ret < 0)
return ret;
if (!(ret & 0x80))
return -EAGAIN;
return ret & 0x7f; /* remove the "valid" bit */
}
/*
* LUX calculation
*/
#define TSL2550_MAX_LUX 1846
static const u8 ratio_lut[] = {
100, 100, 100, 100, 100, 100, 100, 100,
100, 100, 100, 100, 100, 100, 99, 99,
99, 99, 99, 99, 99, 99, 99, 99,
99, 99, 99, 98, 98, 98, 98, 98,
98, 98, 97, 97, 97, 97, 97, 96,
96, 96, 96, 95, 95, 95, 94, 94,
93, 93, 93, 92, 92, 91, 91, 90,
89, 89, 88, 87, 87, 86, 85, 84,
83, 82, 81, 80, 79, 78, 77, 75,
74, 73, 71, 69, 68, 66, 64, 62,
60, 58, 56, 54, 52, 49, 47, 44,
42, 41, 40, 40, 39, 39, 38, 38,
37, 37, 37, 36, 36, 36, 35, 35,
35, 35, 34, 34, 34, 34, 33, 33,
33, 33, 32, 32, 32, 32, 32, 31,
31, 31, 31, 31, 30, 30, 30, 30,
30,
};
static const u16 count_lut[] = {
0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 18, 20, 22, 24, 26, 28, 30,
32, 34, 36, 38, 40, 42, 44, 46,
49, 53, 57, 61, 65, 69, 73, 77,
81, 85, 89, 93, 97, 101, 105, 109,
115, 123, 131, 139, 147, 155, 163, 171,
179, 187, 195, 203, 211, 219, 227, 235,
247, 263, 279, 295, 311, 327, 343, 359,
375, 391, 407, 423, 439, 455, 471, 487,
511, 543, 575, 607, 639, 671, 703, 735,
767, 799, 831, 863, 895, 927, 959, 991,
1039, 1103, 1167, 1231, 1295, 1359, 1423, 1487,
1551, 1615, 1679, 1743, 1807, 1871, 1935, 1999,
2095, 2223, 2351, 2479, 2607, 2735, 2863, 2991,
3119, 3247, 3375, 3503, 3631, 3759, 3887, 4015,
};
/*
* This function is described into Taos TSL2550 Designer's Notebook
* pages 2, 3.
*/
static int tsl2550_calculate_lux(u8 ch0, u8 ch1)
{
unsigned int lux;
/* Look up count from channel values */
u16 c0 = count_lut[ch0];
u16 c1 = count_lut[ch1];
/*
* Calculate ratio.
* Note: the "128" is a scaling factor
*/
u8 r = 128;
/* Avoid division by 0 and count 1 cannot be greater than count 0 */
if (c1 <= c0)
if (c0) {
r = c1 * 128 / c0;
/* Calculate LUX */
lux = ((c0 - c1) * ratio_lut[r]) / 256;
} else
lux = 0;
else
return -EAGAIN;
/* LUX range check */
return lux > TSL2550_MAX_LUX ? TSL2550_MAX_LUX : lux;
}
/*
* SysFS support
*/
static ssize_t tsl2550_show_power_state(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));
return sprintf(buf, "%u\n", data->power_state);
}
static ssize_t tsl2550_store_power_state(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct i2c_client *client = to_i2c_client(dev);
struct tsl2550_data *data = i2c_get_clientdata(client);
unsigned long val = simple_strtoul(buf, NULL, 10);
int ret;
if (val < 0 || val > 1)
return -EINVAL;
mutex_lock(&data->update_lock);
ret = tsl2550_set_power_state(client, val);
mutex_unlock(&data->update_lock);
if (ret < 0)
return ret;
return count;
}
static DEVICE_ATTR(power_state, S_IWUSR | S_IRUGO,
tsl2550_show_power_state, tsl2550_store_power_state);
static ssize_t tsl2550_show_operating_mode(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct tsl2550_data *data = i2c_get_clientdata(to_i2c_client(dev));
return sprintf(buf, "%u\n", data->operating_mode);
}
static ssize_t tsl2550_store_operating_mode(struct device *dev,
struct device_attribute *attr, const char *buf, size_t count)
{
struct i2c_client *client = to_i2c_client(dev);
struct tsl2550_data *data = i2c_get_clientdata(client);
unsigned long val = simple_strtoul(buf, NULL, 10);
int ret;
if (val < 0 || val > 1)
return -EINVAL;
if (data->power_state == 0)
return -EBUSY;
mutex_lock(&data->update_lock);
ret = tsl2550_set_operating_mode(client, val);
mutex_unlock(&data->update_lock);
if (ret < 0)
return ret;
return count;
}
static DEVICE_ATTR(operating_mode, S_IWUSR | S_IRUGO,
tsl2550_show_operating_mode, tsl2550_store_operating_mode);
static ssize_t __tsl2550_show_lux(struct i2c_client *client, char *buf)
{
u8 ch0, ch1;
int ret;
ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC0);
if (ret < 0)
return ret;
ch0 = ret;
ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC1);
if (ret < 0)
return ret;
ch1 = ret;
/* Do the job */
ret = tsl2550_calculate_lux(ch0, ch1);
if (ret < 0)
return ret;
return sprintf(buf, "%d\n", ret);
}
static ssize_t tsl2550_show_lux1_input(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct i2c_client *client = to_i2c_client(dev);
struct tsl2550_data *data = i2c_get_clientdata(client);
int ret;
/* No LUX data if not operational */
if (!data->power_state)
return -EBUSY;
mutex_lock(&data->update_lock);
ret = __tsl2550_show_lux(client, buf);
mutex_unlock(&data->update_lock);
return ret;
}
static DEVICE_ATTR(lux1_input, S_IRUGO,
tsl2550_show_lux1_input, NULL);
static struct attribute *tsl2550_attributes[] = {
&dev_attr_power_state.attr,
&dev_attr_operating_mode.attr,
&dev_attr_lux1_input.attr,
NULL
};
static const struct attribute_group tsl2550_attr_group = {
.attrs = tsl2550_attributes,
};
/*
* Initialization function
*/
static int tsl2550_init_client(struct i2c_client *client)
{
struct tsl2550_data *data = i2c_get_clientdata(client);
int err;
/*
* Probe the chip. To do so we try to power up the device and then to
* read back the 0x03 code
*/
err = i2c_smbus_read_byte_data(client, TSL2550_POWER_UP);
if (err < 0)
return err;
if (err != TSL2550_POWER_UP)
return -ENODEV;
data->power_state = 1;
/* Set the default operating mode */
err = i2c_smbus_write_byte(client,
TSL2550_MODE_RANGE[data->operating_mode]);
if (err < 0)
return err;
return 0;
}
/*
* I2C init/probing/exit functions
*/
static struct i2c_driver tsl2550_driver;
static int __devinit tsl2550_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
struct tsl2550_data *data;
int *opmode, err = 0;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE
| I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
err = -EIO;
goto exit;
}
data = kzalloc(sizeof(struct tsl2550_data), GFP_KERNEL);
if (!data) {
err = -ENOMEM;
goto exit;
}
data->client = client;
i2c_set_clientdata(client, data);
/* Check platform data */
opmode = client->dev.platform_data;
if (opmode) {
if (*opmode < 0 || *opmode > 1) {
dev_err(&client->dev, "invalid operating_mode (%d)\n",
*opmode);
err = -EINVAL;
goto exit_kfree;
}
data->operating_mode = *opmode;
} else
data->operating_mode = 0; /* default mode is standard */
dev_info(&client->dev, "%s operating mode\n",
data->operating_mode ? "extended" : "standard");
mutex_init(&data->update_lock);
/* Initialize the TSL2550 chip */
err = tsl2550_init_client(client);
if (err)
goto exit_kfree;
/* Register sysfs hooks */
err = sysfs_create_group(&client->dev.kobj, &tsl2550_attr_group);
if (err)
goto exit_kfree;
dev_info(&client->dev, "support ver. %s enabled\n", DRIVER_VERSION);
return 0;
exit_kfree:
kfree(data);
exit:
return err;
}
static int __devexit tsl2550_remove(struct i2c_client *client)
{
sysfs_remove_group(&client->dev.kobj, &tsl2550_attr_group);
/* Power down the device */
tsl2550_set_power_state(client, 0);
kfree(i2c_get_clientdata(client));
return 0;
}
#ifdef CONFIG_PM
static int tsl2550_suspend(struct i2c_client *client, pm_message_t mesg)
{
return tsl2550_set_power_state(client, 0);
}
static int tsl2550_resume(struct i2c_client *client)
{
return tsl2550_set_power_state(client, 1);
}
#else
#define tsl2550_suspend NULL
#define tsl2550_resume NULL
#endif /* CONFIG_PM */
static const struct i2c_device_id tsl2550_id[] = {
{ "tsl2550", 0 },
{ }
};
MODULE_DEVICE_TABLE(i2c, tsl2550_id);
static struct i2c_driver tsl2550_driver = {
.driver = {
.name = TSL2550_DRV_NAME,
.owner = THIS_MODULE,
},
.suspend = tsl2550_suspend,
.resume = tsl2550_resume,
.probe = tsl2550_probe,
.remove = __devexit_p(tsl2550_remove),
.id_table = tsl2550_id,
};
static int __init tsl2550_init(void)
{
return i2c_add_driver(&tsl2550_driver);
}
static void __exit tsl2550_exit(void)
{
i2c_del_driver(&tsl2550_driver);
}
MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("TSL2550 ambient light sensor driver");
MODULE_LICENSE("GPL");
MODULE_VERSION(DRIVER_VERSION);
module_init(tsl2550_init);
module_exit(tsl2550_exit);
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