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 <[email protected]> Cc: Michele De Candia <[email protected]> Cc: Rodolfo Giometti <[email protected]> --- Michele, Rodolfo, can you please test and confirm the driver still works OK for you? Thanks. drivers/i2c/chips/tsl2550.c | 42 ++++++++++-------------------------------- 1 file changed, 10 insertions(+), 32 deletions(-) --- linux-2.6.31-rc3.orig/drivers/i2c/chips/tsl2550.c 2009-07-15 22:19:51.000000000 +0200 +++ linux-2.6.31-rc3/drivers/i2c/chips/tsl2550.c 2009-07-15 22:20:03.000000000 +0200 @@ -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_set_power_state(struc 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 @@ static ssize_t __tsl2550_show_lux(struct return ret; ch0 = ret; - mdelay(1); - ret = tsl2550_get_adc_value(client, TSL2550_READ_ADC1); if (ret < 0) return ret; @@ -345,11 +323,10 @@ static int tsl2550_init_client(struct i2 * 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 @@ static int __devinit tsl2550_probe(struc 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; } -- Jean Delvare -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
