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>
diff --git a/drivers/i2c/chips/tsl2550.c b/drivers/i2c/chips/tsl2550.c
index b96f302..aa96bd2 100644
--- a/drivers/i2c/chips/tsl2550.c
+++ b/drivers/i2c/chips/tsl2550.c
@@ -24,10 +24,9 @@
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
-#include <linux/delay.h>
#define TSL2550_DRV_NAME "tsl2550"
-#define DRIVER_VERSION "1.1.2"
+#define DRIVER_VERSION "1.2"
/*
* Defines
@@ -96,32 +95,13 @@
static int tsl2550_get_adc_value(struct i2c_client *client, u8 cmd)
{
- unsigned long end;
- int loop = 0, ret = 0;
+ int ret;
- /*
- * Read ADC channel waiting at most 400ms (see data sheet for further
- * info).
- * To avoid long busy wait we spin for few milliseconds then
- * start sleeping.
- */
- end = jiffies + msecs_to_jiffies(400);
- while (time_before(jiffies, end)) {
- i2c_smbus_write_byte(client, cmd);
-
- if (loop++ < 5)
- mdelay(1);
- else
- msleep(1);
-
- ret = i2c_smbus_read_byte(client);
- if (ret < 0)
- return ret;
- else if (ret & 0x0080)
- break;
- }
+ ret = i2c_smbus_read_byte_data(client, cmd);
+ if (ret < 0)
+ return ret;
if (!(ret & 0x80))
- return -EIO;
+ return -EAGAIN;
return ret & 0x7f; /* remove the "valid" bit */
}
@@ -285,8 +265,6 @@
return ret;
ch0 = ret;
- mdelay(1);
-
ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC1);
if (ret < 0)
return ret;
@@ -345,11 +323,10 @@
* Probe the chip. To do so we try to power up the device and then to
* read back the 0x03 code
*/
- err = i2c_smbus_write_byte(client, TSL2550_POWER_UP);
+ err = i2c_smbus_read_byte_data(client, TSL2550_POWER_UP);
if (err < 0)
return err;
- mdelay(1);
- if (i2c_smbus_read_byte(client) != TSL2550_POWER_UP)
+ if (err != TSL2550_POWER_UP)
return -ENODEV;
data->power_state = 1;
@@ -374,7 +351,8 @@
struct tsl2550_data *data;
int *opmode, err = 0;
- if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE)) {
+ if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_WRITE_BYTE
+ | I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
err = -EIO;
goto exit;
}