On Fri, Jan 12, 2018 at 09:42:28PM +0100, Emiliano Ingrassia wrote: > An sht3x sensor include limits register which contains temperature > and humidity limit values. After a reset, pre-defined values are loaded > into that register. During the probe function, the driver reads the > limits register. However, if the reads are made too early, and the bus > is clocked at high frequencies (e.g. 100 kHz or more), the loading could be > not completed and the sensor returns a NACK which causes the probe to fail. > A delay of at least 500 us before the first read solves this issue. > > Signed-off-by: Emiliano Ingrassia <ingrassia@xxxxxxxxxxxxxx> Applied. Thanks, Guenter > --- > drivers/hwmon/sht3x.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/drivers/hwmon/sht3x.c b/drivers/hwmon/sht3x.c > index 6ea99cd6ae79..370b57dafab7 100644 > --- a/drivers/hwmon/sht3x.c > +++ b/drivers/hwmon/sht3x.c > @@ -732,6 +732,13 @@ static int sht3x_probe(struct i2c_client *client, > mutex_init(&data->i2c_lock); > mutex_init(&data->data_lock); > > + /* > + * An attempt to read limits register too early > + * causes a NACK response from the chip. > + * Waiting for an empirical delay of 500 us solves the issue. > + */ > + usleep_range(500, 600); > + > ret = limits_update(data); > if (ret) > return ret; > -- > 2.15.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
